{"type":"file-history-snapshot","messageId":"7fe64e31-f76e-403e-88ab-3a6e6ef368e7","snapshot":{"messageId":"7fe64e31-f76e-403e-88ab-3a6e6ef368e7","trackedFileBackups":{},"timestamp":"2026-03-29T09:04:51.569Z"},"isSnapshotUpdate":false} {"parentUuid":null,"isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":"Previously the throughput of the wal rotation was improved. But it is still not sufficient. It seems that on top of a continous metric instream there are also bursts of metric data. The problem occurs when a checkpoint is written: 3/29/2026, 8:06:02 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1440001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:01 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1430001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:01 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1420001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:01 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1410001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1400001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1390001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1380001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1370001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1360001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1350001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1340001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1330001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1320001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1310001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1300001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1290001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1280001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1270001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1260001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1250001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1240001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1230001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1220001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1210001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1200001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1190001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1180001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1170001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1160001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1150001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1140001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1130001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1120001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1110001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1100001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1090001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1080001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1070001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1060001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1050001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1040001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1030001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1020001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1010001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 1000001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 990001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 980001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 970001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 960001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 950001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 940001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 930001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 920001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 910001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 900001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 890001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 880001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 870001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 860001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 850001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 840001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 830001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 820001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 810001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 800001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 790001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 780001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 770001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 760001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 750001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 740001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 730001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 720001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 710001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 700001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 690001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:06:00 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 680001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 670001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 660001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 580001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 650001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 640001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 630001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 620001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 610001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 600001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 590001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 570001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 560001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 550001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 540001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 530001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 520001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 510001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:59 AMWARN[WARNING] lineprotocol.go:368: [METRICSTORE]> WAL shard channel full, dropped 500001 messages (data safe in memory, next snapshot will capture)\n3/29/2026, 8:05:50 AMINFO[INFO] walCheckpoint.go:690: [METRICSTORE]> Starting binary checkpoint for 1845 hosts with 10 workers . Analyze the problem, improve the throughput and fix the issue."},"uuid":"7fe64e31-f76e-403e-88ab-3a6e6ef368e7","timestamp":"2026-03-29T09:04:50.967Z","permissionMode":"plan","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"7fe64e31-f76e-403e-88ab-3a6e6ef368e7","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01XGtEscuC1rETxmGJfqSnBg","type":"message","role":"assistant","content":[{"type":"thinking","thinking":"","signature":"EqICClkIDBgCKkB2CLeNWm788Q326O8gA9K1qtPETPJd9Z0s3vKRX94gL5/QL4fthplqSR5Tv6sOdKd2BtG+uo5vKbucgahOaG06Mg9jbGF1ZGUtb3B1cy00LTY4ABIMvW4p3p5O8xZrHZXsGgyZAJ8W2aYdUl14G9AiMAccnsEEqEzFnBsF1jIWbfFpPxld0LZFyfcUDOT8WGz1icGX4lDbjyh2Efvx0a4zLCp3pnIJwUlGLU9Xh0YRX22SFdZC3dM4ja1+M3ZBCo0ApuyxZaIft8AnApuRMfjd9KJu9RuPnhHSw4VlCriLv0qY04snhz5wqujOrG4AHlxUf5wrphTos0fzyTzbK3bE64hJGSuOymsSZZGuX+eVpsKvrnksmr/ymLcYAQ=="}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":15379,"cache_read_input_tokens":11336,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":15379},"output_tokens":30,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX6yex5WpbVuZgtwqkqX","type":"assistant","uuid":"5897dd72-2f4f-40c0-aa19-44921924772d","timestamp":"2026-03-29T09:04:55.681Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"5897dd72-2f4f-40c0-aa19-44921924772d","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01XGtEscuC1rETxmGJfqSnBg","type":"message","role":"assistant","content":[{"type":"text","text":"Let me explore the codebase to understand the current WAL pipeline and identify the bottleneck."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":15379,"cache_read_input_tokens":11336,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":15379},"output_tokens":30,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX6yex5WpbVuZgtwqkqX","type":"assistant","uuid":"b5ca9df0-bc26-4a40-96ce-3969f86ea362","timestamp":"2026-03-29T09:04:56.120Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"b5ca9df0-bc26-4a40-96ce-3969f86ea362","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01XGtEscuC1rETxmGJfqSnBg","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01XsF7urfc4THpBjxNhwGqXR","name":"Agent","input":{"subagent_type":"Explore","description":"Explore WAL pipeline architecture","prompt":"I need to understand the WAL (Write-Ahead Log) pipeline in the metricstore package to diagnose a throughput bottleneck. Specifically:\n\n1. In `pkg/metricstore/lineprotocol.go`: Find the WAL message sending code around line 368, the WAL shard channel setup, the `WALMessage` struct, and how messages are dispatched to shards. Look for channel sizes, the non-blocking send pattern, and the drop/warning logic.\n\n2. In `pkg/metricstore/walCheckpoint.go`: Find the `WALStaging` goroutine (or equivalent shard consumer), the binary checkpoint writing code (around line 690), and the `RotateWALFiles` function. I need to understand what happens during checkpointing — does writing a checkpoint block the WAL consumer?\n\n3. In `pkg/metricstore/metricstore.go`: Find where WAL channels are initialized, their buffer sizes, how many shards/workers are created, and the `Init()` / `Shutdown()` flow.\n\nRead these files thoroughly and report back the complete architecture: channel sizes, number of shards, what blocks what during checkpointing, and where the bottleneck likely is."},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":15379,"cache_read_input_tokens":11336,"output_tokens":430,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":15379,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX6yex5WpbVuZgtwqkqX","type":"assistant","uuid":"2ede8e48-fd56-4eab-b141-85c7223b5d69","timestamp":"2026-03-29T09:05:03.204Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"2ede8e48-fd56-4eab-b141-85c7223b5d69","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01XsF7urfc4THpBjxNhwGqXR","type":"tool_result","content":[{"type":"text","text":"Perfect! Now I have all the information I need. Let me create a comprehensive analysis document:\n\n## Complete WAL Pipeline Architecture Analysis\n\nBased on my thorough examination of the three key files, here is the complete architecture of the WAL pipeline and where the throughput bottleneck likely exists:\n\n---\n\n### **1. CHANNEL CONFIGURATION & SHARD DISPATCH**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/lineprotocol.go` (lines 355-371)\n\n**WAL Message Structure** (`lineprotocol.go` line 356-363):\n```go\ntype WALMessage struct {\n MetricName string\n Cluster string\n Node string\n Selector []string\n Value schema.Float\n Timestamp int64\n}\n```\n\n**Sending Pattern** (line 364):\n- Non-blocking send using `select` with `default` case\n- Returns `false` if shard channel is full\n- Dropped messages tracked via `walDropped` atomic counter\n- Warning logged every 10,000 drops (line 368)\n\n---\n\n### **2. SHARD CHANNEL SETUP & SIZING**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go` (lines 162-176)\n\n**Initialization** (lines 167-176):\n```go\nwalNumShards = max(Keys.NumWorkers, 1)\nchBufSize := max(65536/walNumShards, 1024)\n\nwalShardChs = make([]chan *WALMessage, walNumShards)\nwalShardRotateChs = make([]chan walRotateReq, walNumShards)\n\nfor i := range walNumShards {\n walShardChs[i] = make(chan *WALMessage, chBufSize)\n walShardRotateChs[i] = make(chan walRotateReq, 64)\n}\n```\n\n**Key Parameters:**\n- **Number of Shards:** Equal to `Keys.NumWorkers` (configurable, defaults to `min(runtime.NumCPU()/2+1, 10)`)\n- **Channel Buffer Size per Shard:** `max(65536/walNumShards, 1024)`\n - Default assumption: if `NumWorkers=4`, then `chBufSize = max(16384, 1024) = 16,384` messages per shard\n - If `NumWorkers=8`, then `chBufSize = max(8192, 1024) = 8,192` messages per shard\n - **Total system capacity:** ~65,536 buffered WAL messages across all shards\n- **Rotation Channel Buffer:** 64 (fixed, small - for rotation signaling only)\n\n**Message Routing** (lines 135-141, 145-156):\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n shard := walShardIndex(msg.Cluster, msg.Node)\n select {\n case walShardChs[shard] <- msg:\n return true\n default:\n return false\n }\n}\n```\n- Uses FNV-1a hash of `cluster+node` to determine shard\n- Each host affinity maintained within a shard (good for locality)\n\n---\n\n### **3. WAL STAGING GOROUTINE (Consumer Side)**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go` (lines 162-342)\n\n**Architecture (lines 178-341):**\n- Creates `walNumShards` independent goroutines (one per shard)\n- Each goroutine:\n - Maintains a `map[string]*walFileState` for open host WAL files\n - Receives messages from its dedicated `msgCh` (non-blocking)\n - Receives rotation requests from `rotateCh`\n - Drains up to 4,096 messages per batch (line 300)\n - Flushes dirty files every `walFlushInterval = 1 second` (line 131)\n\n**Critical Blocking Point - The Checkpoint Write Process:**\n\n```go\ncf, err := l.toCheckpointFile(from, to, m) // Locks Level tree, reads buffers\n```\n\nThis happens inside:\n- `ToCheckpointWAL()` (walCheckpoint.go lines 658-760)\n- `toCheckpointBinary()` (walCheckpoint.go lines 764-800)\n\n**Blocking Sequence During Checkpointing:**\n\n1. **toCheckpointFile** (checkpoint.go lines 264-327):\n - Acquires **RLock** on the Level tree for **each host** (line 265)\n - Holds lock while reading buffer data (lines 276-309)\n - For each metric buffer: calls `b.read(from, to, data)` while holding the lock\n - Recursively processes child levels (line 312) - **tree traversal under lock**\n - Lock remains held until entire subtree is serialized to memory\n\n2. **Write to Disk:**\n - No locks held during file I/O (disk writes are async)\n - Uses atomic write pattern: write to `.tmp` then rename\n\n**Worker Pool During Checkpointing:**\n- `ToCheckpointWAL()` uses `Keys.NumWorkers` parallel workers (line 697)\n- Creates work queue with `Keys.NumWorkers*2` buffer (line 698)\n- Each worker calls `level.toCheckpointBinary()` → `level.toCheckpointFile()`\n\n---\n\n### **4. MEMORY STORE & WRITE SIDE LOCKING**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/metricstore.go` (lines 658-686)\n\n**WriteToLevel Function** (lines 658-686):\n```go\nfunc (m *MemoryStore) WriteToLevel(l *Level, selector []string, ts int64, metrics []Metric) error {\n l = l.findLevelOrCreate(selector, len(m.Metrics))\n l.lock.Lock() // ← WRITE LOCK acquired here\n defer l.lock.Unlock()\n \n for _, metric := range metrics {\n // ... write to buffers ...\n }\n return nil\n}\n```\n\n**Lock Hierarchy:**\n- **Write path:** `WriteToLevel()` takes **Lock()** (exclusive) on target Level\n- **Checkpoint read path:** `toCheckpointFile()` takes **RLock()** (shared) on Level\n- **Contention point:** When checkpoint is in progress:\n - All writes to that host's Level are **blocked** (waiting for RLock release)\n - RLock holds entire host's Level while serializing all metrics + children\n\n---\n\n### **5. INITIALIZATION & WORKER CONFIGURATION**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/metricstore.go` (lines 124-193)\n\n**Default Worker Count** (config.go lines 52-57, metricstore.go lines 136-140):\n```go\nconst DefaultMaxWorkers = 10\n\nif Keys.NumWorkers <= 0 {\n Keys.NumWorkers = min(runtime.NumCPU()/2+1, DefaultMaxWorkers)\n}\n```\n\n**Initialization Order** (lines 172-176):\n1. `Retention()` - garbage collection goroutine\n2. `Checkpointing()` - periodic snapshot creator\n3. `CleanUp()` - archive worker\n4. `WALStaging()` - **WAL consumer goroutines** ← Started here\n5. `MemoryUsageTracker()` - emergency free handler\n\n**Shutdown Flow** (metricstore.go lines 273-320):\n- Sets `walShuttingDown.Store(true)` (line 286)\n- Sleeps 100ms to allow in-flight DecodeLine calls to complete (line 288)\n- Closes all `walShardChs` (line 290-292)\n- Waits for `WaitForWALStagingDrain()` (line 294)\n- Writes final checkpoint (line 311)\n\n---\n\n### **6. THE BOTTLENECK - DETAILED ANALYSIS**\n\n**Root Cause: Double Locking During Checkpointing**\n\nThe throughput bottleneck occurs at the intersection of three factors:\n\n1. **WAL Message Production Rate**\n - Decoder threads send messages to shard channels (non-blocking)\n - Buffer capacity: ~65,536 messages total across all shards\n - When full → messages dropped (logged as warnings)\n\n2. **WAL Staging Consumption Rate**\n - Each shard goroutine processes up to 4,096 messages per batch\n - Flushes every 1 second to disk\n - Normal case: no congestion, messages flow through\n\n3. **Checkpoint Write Contention** ← **THE BOTTLENECK**\n \n During periodic checkpoint (every 12 hours by default):\n \n ```\n Checkpointing goroutine:\n ├─ Call ToCheckpointWAL() for all N hosts\n │ ├─ Start Keys.NumWorkers checkpoint workers\n │ └─ Each worker processes host in parallel:\n │ └─ toCheckpointBinary(hostDir) \n │ └─ toCheckpointFile()\n │ └─ l.lock.RLock() ← BLOCKS new writes to Level\n │ └─ Serialize all metrics ← Holds lock for duration\n │ └─ Recursive child traversal ← Lock held for entire subtree\n │ └─ l.lock.RUnlock()\n │ └─ File I/O (disk write)\n │\n └─ After completion: RotateWALFiles(hostDirs)\n └─ Sends rotation requests via walShardRotateChs\n └─ WAL staging goroutines process rotation\n └─ Delete current.wal for each host\n \n DecodeLine threads (in parallel):\n └─ WriteToLevel(cluster, host, ...)\n └─ l.lock.Lock() ← BLOCKS waiting for RLock\n (DEADLOCK if checkpoint reader doesn't release)\n ```\n\n **Lock contention window:** The time `toCheckpointFile()` holds `RLock` on a Level\n - Depends on: number of metrics, size of metric buffers, tree depth\n - Multiply by: number of hosts being checkpointed simultaneously\n - With `Keys.NumWorkers=4`: up to 4 hosts locked simultaneously\n - With `Keys.NumWorkers=8`: up to 8 hosts locked simultaneously\n\n4. **WAL Channel Backpressure**\n - While writes are blocked waiting for checkpoint to complete:\n - `DecodeLine()` threads accumulate in `WriteToLevel()` lock wait queues\n - New WAL messages from NATS are still produced\n - Shard channels fill up (65,536 buffer max)\n - Once full → messages dropped silently\n - Dropped messages logged every 10,000 (walDropped counter)\n\n---\n\n### **7. SPECIFIC BLOCKING SCENARIOS**\n\n**Scenario A: Checkpoint Duration > Message Batch Time**\n```\nt=0ms: Checkpoint starts, locks host \"node001\"\nt=50ms: NATS delivers batch of 10,000 metrics for \"node001\"\nt=50ms: DecodeLine calls WriteToLevel() → blocks on l.lock.Lock()\nt=100ms: Checkpoint finishes, releases RLock\nt=100ms: WriteToLevel() acquires lock, writes buffered data\nt=100ms: WAL messages finally enqueued to shard channel\nResult: 50ms latency added per host per checkpoint\n```\n\n**Scenario B: WAL Channel Saturation**\n```\nt=0ms: Checkpoint running on hosts 1-4 (4 workers)\nt=0ms: NATS rate spike: 50,000 messages/sec for hosts not being checkpointed\nt=10ms: 65,536 shard channel buffers fill\nt=10ms: SendWALMessage() returns false → messages dropped\nt=20ms: Warning logged: \"dropped 10,001 messages\"\nt=120ms: Checkpoint completes\nt=120ms: Writer threads resume → WAL messages enqueue normally\nResult: Bursty throughput, packet loss during checkpoint windows\n```\n\n**Scenario C: Read-Write Priority Inversion** \n```\nLine 624-636 in walCheckpoint.go:\n lvl.lock.Lock() ← WAL replay during startup\n b = lvl.metrics[...]\n b.write(timestamp, value) ← Writes to buffer while checkpoint reader holds RLock\n lvl.lock.Unlock()\n\nDuring startup FromCheckpoint():\n → Replays WAL into buffers (holding exclusive locks per level)\n → Simultaneously: DecodeLine threads try to write new metrics\n → Contention: NewMetrics vs replay writes\n```\n\n---\n\n### **8. SUMMARY: WHERE THE BOTTLENECK IS**\n\n| Component | Location | Capacity | Bottleneck Severity |\n|-----------|----------|----------|-------------------|\n| **WAL Shard Channels** | walCheckpoint.go:174 | 65,536 total msgs | MODERATE - fills during checkpoint |\n| **toCheckpointFile RLock** | checkpoint.go:265 | Duration-based | **SEVERE - blocks writes for N*100ms** |\n| **Checkpoint Workers** | walCheckpoint.go:697 | Keys.NumWorkers | MODERATE - locks up to N hosts |\n| **WAL Flush Interval** | walCheckpoint.go:131 | 1 second | LOW - async to message flow |\n| **Rotation Blocking** | walCheckpoint.go:357-384 | 2 min timeout | MODERATE - can deadlock on error |\n\n**PRIMARY BOTTLENECK:**\nThe `toCheckpointFile()` function's `RLock` on Level nodes during the periodic checkpoint (every 12 hours) blocks **all writes to those hosts**, causing:\n1. NATS message ingestion to stall\n2. WAL shard channels to fill and drop messages\n3. Throughput cliff at checkpoint time\n4. Data loss (dropped messages safe only if next binary snapshot captures them)\n\n**RECOMMENDATION:**\nTo diagnose the exact impact, search logs for:\n- `\"WAL shard channel full, dropped %d messages\"` patterns at checkpoint times\n- Gaps in checkpoint intervals (should be 12h, check if extended)\n- Correlation between checkpoint windows and metric ingestion drops"}]}]},"uuid":"b1d96c9d-3f30-40d4-ba81-0fcc7b738f85","timestamp":"2026-03-29T09:06:25.123Z","toolUseResult":{"status":"completed","prompt":"I need to understand the WAL (Write-Ahead Log) pipeline in the metricstore package to diagnose a throughput bottleneck. Specifically:\n\n1. In `pkg/metricstore/lineprotocol.go`: Find the WAL message sending code around line 368, the WAL shard channel setup, the `WALMessage` struct, and how messages are dispatched to shards. Look for channel sizes, the non-blocking send pattern, and the drop/warning logic.\n\n2. In `pkg/metricstore/walCheckpoint.go`: Find the `WALStaging` goroutine (or equivalent shard consumer), the binary checkpoint writing code (around line 690), and the `RotateWALFiles` function. I need to understand what happens during checkpointing — does writing a checkpoint block the WAL consumer?\n\n3. In `pkg/metricstore/metricstore.go`: Find where WAL channels are initialized, their buffer sizes, how many shards/workers are created, and the `Init()` / `Shutdown()` flow.\n\nRead these files thoroughly and report back the complete architecture: channel sizes, number of shards, what blocks what during checkpointing, and where the bottleneck likely is.","agentId":"ac99bc6c2f1c0febc","agentType":"Explore","content":[{"type":"text","text":"Perfect! Now I have all the information I need. Let me create a comprehensive analysis document:\n\n## Complete WAL Pipeline Architecture Analysis\n\nBased on my thorough examination of the three key files, here is the complete architecture of the WAL pipeline and where the throughput bottleneck likely exists:\n\n---\n\n### **1. CHANNEL CONFIGURATION & SHARD DISPATCH**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/lineprotocol.go` (lines 355-371)\n\n**WAL Message Structure** (`lineprotocol.go` line 356-363):\n```go\ntype WALMessage struct {\n MetricName string\n Cluster string\n Node string\n Selector []string\n Value schema.Float\n Timestamp int64\n}\n```\n\n**Sending Pattern** (line 364):\n- Non-blocking send using `select` with `default` case\n- Returns `false` if shard channel is full\n- Dropped messages tracked via `walDropped` atomic counter\n- Warning logged every 10,000 drops (line 368)\n\n---\n\n### **2. SHARD CHANNEL SETUP & SIZING**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go` (lines 162-176)\n\n**Initialization** (lines 167-176):\n```go\nwalNumShards = max(Keys.NumWorkers, 1)\nchBufSize := max(65536/walNumShards, 1024)\n\nwalShardChs = make([]chan *WALMessage, walNumShards)\nwalShardRotateChs = make([]chan walRotateReq, walNumShards)\n\nfor i := range walNumShards {\n walShardChs[i] = make(chan *WALMessage, chBufSize)\n walShardRotateChs[i] = make(chan walRotateReq, 64)\n}\n```\n\n**Key Parameters:**\n- **Number of Shards:** Equal to `Keys.NumWorkers` (configurable, defaults to `min(runtime.NumCPU()/2+1, 10)`)\n- **Channel Buffer Size per Shard:** `max(65536/walNumShards, 1024)`\n - Default assumption: if `NumWorkers=4`, then `chBufSize = max(16384, 1024) = 16,384` messages per shard\n - If `NumWorkers=8`, then `chBufSize = max(8192, 1024) = 8,192` messages per shard\n - **Total system capacity:** ~65,536 buffered WAL messages across all shards\n- **Rotation Channel Buffer:** 64 (fixed, small - for rotation signaling only)\n\n**Message Routing** (lines 135-141, 145-156):\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n shard := walShardIndex(msg.Cluster, msg.Node)\n select {\n case walShardChs[shard] <- msg:\n return true\n default:\n return false\n }\n}\n```\n- Uses FNV-1a hash of `cluster+node` to determine shard\n- Each host affinity maintained within a shard (good for locality)\n\n---\n\n### **3. WAL STAGING GOROUTINE (Consumer Side)**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go` (lines 162-342)\n\n**Architecture (lines 178-341):**\n- Creates `walNumShards` independent goroutines (one per shard)\n- Each goroutine:\n - Maintains a `map[string]*walFileState` for open host WAL files\n - Receives messages from its dedicated `msgCh` (non-blocking)\n - Receives rotation requests from `rotateCh`\n - Drains up to 4,096 messages per batch (line 300)\n - Flushes dirty files every `walFlushInterval = 1 second` (line 131)\n\n**Critical Blocking Point - The Checkpoint Write Process:**\n\n```go\ncf, err := l.toCheckpointFile(from, to, m) // Locks Level tree, reads buffers\n```\n\nThis happens inside:\n- `ToCheckpointWAL()` (walCheckpoint.go lines 658-760)\n- `toCheckpointBinary()` (walCheckpoint.go lines 764-800)\n\n**Blocking Sequence During Checkpointing:**\n\n1. **toCheckpointFile** (checkpoint.go lines 264-327):\n - Acquires **RLock** on the Level tree for **each host** (line 265)\n - Holds lock while reading buffer data (lines 276-309)\n - For each metric buffer: calls `b.read(from, to, data)` while holding the lock\n - Recursively processes child levels (line 312) - **tree traversal under lock**\n - Lock remains held until entire subtree is serialized to memory\n\n2. **Write to Disk:**\n - No locks held during file I/O (disk writes are async)\n - Uses atomic write pattern: write to `.tmp` then rename\n\n**Worker Pool During Checkpointing:**\n- `ToCheckpointWAL()` uses `Keys.NumWorkers` parallel workers (line 697)\n- Creates work queue with `Keys.NumWorkers*2` buffer (line 698)\n- Each worker calls `level.toCheckpointBinary()` → `level.toCheckpointFile()`\n\n---\n\n### **4. MEMORY STORE & WRITE SIDE LOCKING**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/metricstore.go` (lines 658-686)\n\n**WriteToLevel Function** (lines 658-686):\n```go\nfunc (m *MemoryStore) WriteToLevel(l *Level, selector []string, ts int64, metrics []Metric) error {\n l = l.findLevelOrCreate(selector, len(m.Metrics))\n l.lock.Lock() // ← WRITE LOCK acquired here\n defer l.lock.Unlock()\n \n for _, metric := range metrics {\n // ... write to buffers ...\n }\n return nil\n}\n```\n\n**Lock Hierarchy:**\n- **Write path:** `WriteToLevel()` takes **Lock()** (exclusive) on target Level\n- **Checkpoint read path:** `toCheckpointFile()` takes **RLock()** (shared) on Level\n- **Contention point:** When checkpoint is in progress:\n - All writes to that host's Level are **blocked** (waiting for RLock release)\n - RLock holds entire host's Level while serializing all metrics + children\n\n---\n\n### **5. INITIALIZATION & WORKER CONFIGURATION**\n\n**File:** `/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/metricstore.go` (lines 124-193)\n\n**Default Worker Count** (config.go lines 52-57, metricstore.go lines 136-140):\n```go\nconst DefaultMaxWorkers = 10\n\nif Keys.NumWorkers <= 0 {\n Keys.NumWorkers = min(runtime.NumCPU()/2+1, DefaultMaxWorkers)\n}\n```\n\n**Initialization Order** (lines 172-176):\n1. `Retention()` - garbage collection goroutine\n2. `Checkpointing()` - periodic snapshot creator\n3. `CleanUp()` - archive worker\n4. `WALStaging()` - **WAL consumer goroutines** ← Started here\n5. `MemoryUsageTracker()` - emergency free handler\n\n**Shutdown Flow** (metricstore.go lines 273-320):\n- Sets `walShuttingDown.Store(true)` (line 286)\n- Sleeps 100ms to allow in-flight DecodeLine calls to complete (line 288)\n- Closes all `walShardChs` (line 290-292)\n- Waits for `WaitForWALStagingDrain()` (line 294)\n- Writes final checkpoint (line 311)\n\n---\n\n### **6. THE BOTTLENECK - DETAILED ANALYSIS**\n\n**Root Cause: Double Locking During Checkpointing**\n\nThe throughput bottleneck occurs at the intersection of three factors:\n\n1. **WAL Message Production Rate**\n - Decoder threads send messages to shard channels (non-blocking)\n - Buffer capacity: ~65,536 messages total across all shards\n - When full → messages dropped (logged as warnings)\n\n2. **WAL Staging Consumption Rate**\n - Each shard goroutine processes up to 4,096 messages per batch\n - Flushes every 1 second to disk\n - Normal case: no congestion, messages flow through\n\n3. **Checkpoint Write Contention** ← **THE BOTTLENECK**\n \n During periodic checkpoint (every 12 hours by default):\n \n ```\n Checkpointing goroutine:\n ├─ Call ToCheckpointWAL() for all N hosts\n │ ├─ Start Keys.NumWorkers checkpoint workers\n │ └─ Each worker processes host in parallel:\n │ └─ toCheckpointBinary(hostDir) \n │ └─ toCheckpointFile()\n │ └─ l.lock.RLock() ← BLOCKS new writes to Level\n │ └─ Serialize all metrics ← Holds lock for duration\n │ └─ Recursive child traversal ← Lock held for entire subtree\n │ └─ l.lock.RUnlock()\n │ └─ File I/O (disk write)\n │\n └─ After completion: RotateWALFiles(hostDirs)\n └─ Sends rotation requests via walShardRotateChs\n └─ WAL staging goroutines process rotation\n └─ Delete current.wal for each host\n \n DecodeLine threads (in parallel):\n └─ WriteToLevel(cluster, host, ...)\n └─ l.lock.Lock() ← BLOCKS waiting for RLock\n (DEADLOCK if checkpoint reader doesn't release)\n ```\n\n **Lock contention window:** The time `toCheckpointFile()` holds `RLock` on a Level\n - Depends on: number of metrics, size of metric buffers, tree depth\n - Multiply by: number of hosts being checkpointed simultaneously\n - With `Keys.NumWorkers=4`: up to 4 hosts locked simultaneously\n - With `Keys.NumWorkers=8`: up to 8 hosts locked simultaneously\n\n4. **WAL Channel Backpressure**\n - While writes are blocked waiting for checkpoint to complete:\n - `DecodeLine()` threads accumulate in `WriteToLevel()` lock wait queues\n - New WAL messages from NATS are still produced\n - Shard channels fill up (65,536 buffer max)\n - Once full → messages dropped silently\n - Dropped messages logged every 10,000 (walDropped counter)\n\n---\n\n### **7. SPECIFIC BLOCKING SCENARIOS**\n\n**Scenario A: Checkpoint Duration > Message Batch Time**\n```\nt=0ms: Checkpoint starts, locks host \"node001\"\nt=50ms: NATS delivers batch of 10,000 metrics for \"node001\"\nt=50ms: DecodeLine calls WriteToLevel() → blocks on l.lock.Lock()\nt=100ms: Checkpoint finishes, releases RLock\nt=100ms: WriteToLevel() acquires lock, writes buffered data\nt=100ms: WAL messages finally enqueued to shard channel\nResult: 50ms latency added per host per checkpoint\n```\n\n**Scenario B: WAL Channel Saturation**\n```\nt=0ms: Checkpoint running on hosts 1-4 (4 workers)\nt=0ms: NATS rate spike: 50,000 messages/sec for hosts not being checkpointed\nt=10ms: 65,536 shard channel buffers fill\nt=10ms: SendWALMessage() returns false → messages dropped\nt=20ms: Warning logged: \"dropped 10,001 messages\"\nt=120ms: Checkpoint completes\nt=120ms: Writer threads resume → WAL messages enqueue normally\nResult: Bursty throughput, packet loss during checkpoint windows\n```\n\n**Scenario C: Read-Write Priority Inversion** \n```\nLine 624-636 in walCheckpoint.go:\n lvl.lock.Lock() ← WAL replay during startup\n b = lvl.metrics[...]\n b.write(timestamp, value) ← Writes to buffer while checkpoint reader holds RLock\n lvl.lock.Unlock()\n\nDuring startup FromCheckpoint():\n → Replays WAL into buffers (holding exclusive locks per level)\n → Simultaneously: DecodeLine threads try to write new metrics\n → Contention: NewMetrics vs replay writes\n```\n\n---\n\n### **8. SUMMARY: WHERE THE BOTTLENECK IS**\n\n| Component | Location | Capacity | Bottleneck Severity |\n|-----------|----------|----------|-------------------|\n| **WAL Shard Channels** | walCheckpoint.go:174 | 65,536 total msgs | MODERATE - fills during checkpoint |\n| **toCheckpointFile RLock** | checkpoint.go:265 | Duration-based | **SEVERE - blocks writes for N*100ms** |\n| **Checkpoint Workers** | walCheckpoint.go:697 | Keys.NumWorkers | MODERATE - locks up to N hosts |\n| **WAL Flush Interval** | walCheckpoint.go:131 | 1 second | LOW - async to message flow |\n| **Rotation Blocking** | walCheckpoint.go:357-384 | 2 min timeout | MODERATE - can deadlock on error |\n\n**PRIMARY BOTTLENECK:**\nThe `toCheckpointFile()` function's `RLock` on Level nodes during the periodic checkpoint (every 12 hours) blocks **all writes to those hosts**, causing:\n1. NATS message ingestion to stall\n2. WAL shard channels to fill and drop messages\n3. Throughput cliff at checkpoint time\n4. Data loss (dropped messages safe only if next binary snapshot captures them)\n\n**RECOMMENDATION:**\nTo diagnose the exact impact, search logs for:\n- `\"WAL shard channel full, dropped %d messages\"` patterns at checkpoint times\n- Gaps in checkpoint intervals (should be 12h, check if extended)\n- Correlation between checkpoint windows and metric ingestion drops"}],"totalDurationMs":81630,"totalTokens":53262,"totalToolUseCount":17,"usage":{"input_tokens":4,"cache_creation_input_tokens":1558,"cache_read_input_tokens":48069,"output_tokens":3631,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":0,"ephemeral_5m_input_tokens":1558},"inference_geo":"","iterations":[],"speed":"standard"}},"sourceToolAssistantUUID":"2ede8e48-fd56-4eab-b141-85c7223b5d69","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"b1d96c9d-3f30-40d4-ba81-0fcc7b738f85","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CXGfsb5WqL8iSNihWTQFVN","type":"message","role":"assistant","content":[{"type":"thinking","thinking":"","signature":"Ep8CClkIDBgCKkAZPetZPq3xElJZEC7Xh/EYobN5rxAjYC3/iTDCl8Xl8BQLm3abQNHiwehImRKdgJNbKy2+iIKddVExcTHdQkczMg9jbGF1ZGUtb3B1cy00LTY4ABIMlm5+a7me770scxixGgxZevjX4hmNzlZCMQ0iMLsRqo/wbG9LZhIsRdE05qLNKHWXkKpl3dkgAlCKWLxm+DA9gWNqsUgPAGOTpxvUPyp0lQX2vv0D81EhPZhQVaDIUGBEgaayLGgVlE3D5x+kyFtleWVuJ9elbFhcsrfx6JM2w/WkKUxhA3QzBnUvTHKVFt8yGx4KY2kZzXaHk1Ilkm66DCPOcFzNtt2eYtWXmZajRUyb0p2L2cxLhELbOtvxojPmFWoYAQ=="}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":4071,"cache_read_input_tokens":26715,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":4071},"output_tokens":23,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX76a5antaHx7rUY5XAx","type":"assistant","uuid":"af52bdc1-d14a-4190-a086-188d9526616e","timestamp":"2026-03-29T09:06:28.674Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"af52bdc1-d14a-4190-a086-188d9526616e","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CXGfsb5WqL8iSNihWTQFVN","type":"message","role":"assistant","content":[{"type":"text","text":"Let me read the critical code sections directly to verify the analysis and understand the exact implementation."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":4071,"cache_read_input_tokens":26715,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":4071},"output_tokens":23,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX76a5antaHx7rUY5XAx","type":"assistant","uuid":"4359185b-af67-4d59-991d-c704aeb4297a","timestamp":"2026-03-29T09:06:29.573Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"4359185b-af67-4d59-991d-c704aeb4297a","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CXGfsb5WqL8iSNihWTQFVN","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01685vRuUKmqmTNAPYV5ptBU","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","limit":100,"offset":125},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":4071,"cache_read_input_tokens":26715,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":4071},"output_tokens":23,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX76a5antaHx7rUY5XAx","type":"assistant","uuid":"6b40151a-90ea-43cc-a426-fab93e2e4319","timestamp":"2026-03-29T09:06:30.114Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"6b40151a-90ea-43cc-a426-fab93e2e4319","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01685vRuUKmqmTNAPYV5ptBU","type":"tool_result","content":"125\t\tsize int64 // approximate bytes written (tracked from open + writes)\n126\t}\n127\t\n128\t// walFlushInterval controls how often dirty WAL files are flushed to disk.\n129\t// Decoupling flushes from message processing lets the consumer run at memory\n130\t// speed, amortizing syscall overhead across many writes.\n131\tconst walFlushInterval = 1 * time.Second\n132\t\n133\t// walShardIndex computes which shard a message belongs to based on cluster+node.\n134\t// Uses FNV-1a hash for fast, well-distributed mapping.\n135\tfunc walShardIndex(cluster, node string) int {\n136\t\th := fnv.New32a()\n137\t\th.Write([]byte(cluster))\n138\t\th.Write([]byte{0})\n139\t\th.Write([]byte(node))\n140\t\treturn int(h.Sum32()) % walNumShards\n141\t}\n142\t\n143\t// SendWALMessage routes a WAL message to the appropriate shard channel.\n144\t// Returns false if the channel is full or shutdown is in progress.\n145\tfunc SendWALMessage(msg *WALMessage) bool {\n146\t\tif walShardChs == nil || walShuttingDown.Load() {\n147\t\t\treturn false\n148\t\t}\n149\t\tshard := walShardIndex(msg.Cluster, msg.Node)\n150\t\tselect {\n151\t\tcase walShardChs[shard] <- msg:\n152\t\t\treturn true\n153\t\tdefault:\n154\t\t\treturn false\n155\t\t}\n156\t}\n157\t\n158\t// WALStaging starts N sharded background goroutines that receive WALMessage items\n159\t// and append binary WAL records to per-host current.wal files.\n160\t// Each shard owns a subset of hosts (determined by hash of cluster+node),\n161\t// parallelizing serialization and I/O while keeping per-host writes serial.\n162\tfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n163\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n164\t\t\treturn\n165\t\t}\n166\t\n167\t\twalNumShards = max(Keys.NumWorkers, 1)\n168\t\tchBufSize := max(65536/walNumShards, 1024)\n169\t\n170\t\twalShardChs = make([]chan *WALMessage, walNumShards)\n171\t\twalShardRotateChs = make([]chan walRotateReq, walNumShards)\n172\t\n173\t\tfor i := range walNumShards {\n174\t\t\twalShardChs[i] = make(chan *WALMessage, chBufSize)\n175\t\t\twalShardRotateChs[i] = make(chan walRotateReq, 64)\n176\t\t}\n177\t\n178\t\tfor i := range walNumShards {\n179\t\t\tmsgCh := walShardChs[i]\n180\t\t\trotateCh := walShardRotateChs[i]\n181\t\n182\t\t\twalStagingWg.Add(1)\n183\t\t\twg.Go(func() {\n184\t\t\t\tdefer walStagingWg.Done()\n185\t\t\t\thostFiles := make(map[string]*walFileState)\n186\t\n187\t\t\t\tdefer func() {\n188\t\t\t\t\tfor _, ws := range hostFiles {\n189\t\t\t\t\t\tif ws.f != nil {\n190\t\t\t\t\t\t\tws.w.Flush()\n191\t\t\t\t\t\t\tws.f.Close()\n192\t\t\t\t\t\t}\n193\t\t\t\t\t}\n194\t\t\t\t}()\n195\t\n196\t\t\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n197\t\t\t\t\tws, ok := hostFiles[hostDir]\n198\t\t\t\t\tif ok {\n199\t\t\t\t\t\treturn ws\n200\t\t\t\t\t}\n201\t\n202\t\t\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n203\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n204\t\t\t\t\t\treturn nil\n205\t\t\t\t\t}\n206\t\n207\t\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n208\t\t\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n209\t\t\t\t\tif err != nil {\n210\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n211\t\t\t\t\t\treturn nil\n212\t\t\t\t\t}\n213\t\n214\t\t\t\t\tw := bufio.NewWriter(f)\n215\t\n216\t\t\t\t\t// Write file header magic if file is new (empty).\n217\t\t\t\t\tinfo, err := f.Stat()\n218\t\t\t\t\tvar fileSize int64\n219\t\t\t\t\tif err == nil {\n220\t\t\t\t\t\tfileSize = info.Size()\n221\t\t\t\t\t}\n222\t\t\t\t\tif err == nil && fileSize == 0 {\n223\t\t\t\t\t\tvar hdr [4]byte\n224\t\t\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)"}]},"uuid":"588525d6-4d3f-49c3-8b7e-f07c50e4dcc8","timestamp":"2026-03-29T09:06:30.130Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"\tsize int64 // approximate bytes written (tracked from open + writes)\n}\n\n// walFlushInterval controls how often dirty WAL files are flushed to disk.\n// Decoupling flushes from message processing lets the consumer run at memory\n// speed, amortizing syscall overhead across many writes.\nconst walFlushInterval = 1 * time.Second\n\n// walShardIndex computes which shard a message belongs to based on cluster+node.\n// Uses FNV-1a hash for fast, well-distributed mapping.\nfunc walShardIndex(cluster, node string) int {\n\th := fnv.New32a()\n\th.Write([]byte(cluster))\n\th.Write([]byte{0})\n\th.Write([]byte(node))\n\treturn int(h.Sum32()) % walNumShards\n}\n\n// SendWALMessage routes a WAL message to the appropriate shard channel.\n// Returns false if the channel is full or shutdown is in progress.\nfunc SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}\n\n// WALStaging starts N sharded background goroutines that receive WALMessage items\n// and append binary WAL records to per-host current.wal files.\n// Each shard owns a subset of hosts (determined by hash of cluster+node),\n// parallelizing serialization and I/O while keeping per-host writes serial.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\treturn\n\t}\n\n\twalNumShards = max(Keys.NumWorkers, 1)\n\tchBufSize := max(65536/walNumShards, 1024)\n\n\twalShardChs = make([]chan *WALMessage, walNumShards)\n\twalShardRotateChs = make([]chan walRotateReq, walNumShards)\n\n\tfor i := range walNumShards {\n\t\twalShardChs[i] = make(chan *WALMessage, chBufSize)\n\t\twalShardRotateChs[i] = make(chan walRotateReq, 64)\n\t}\n\n\tfor i := range walNumShards {\n\t\tmsgCh := walShardChs[i]\n\t\trotateCh := walShardRotateChs[i]\n\n\t\twalStagingWg.Add(1)\n\t\twg.Go(func() {\n\t\t\tdefer walStagingWg.Done()\n\t\t\thostFiles := make(map[string]*walFileState)\n\n\t\t\tdefer func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.f != nil {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.f.Close()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}()\n\n\t\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\t\tws, ok := hostFiles[hostDir]\n\t\t\t\tif ok {\n\t\t\t\t\treturn ws\n\t\t\t\t}\n\n\t\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t\t// Write file header magic if file is new (empty).\n\t\t\t\tinfo, err := f.Stat()\n\t\t\t\tvar fileSize int64\n\t\t\t\tif err == nil {\n\t\t\t\t\tfileSize = info.Size()\n\t\t\t\t}\n\t\t\t\tif err == nil && fileSize == 0 {\n\t\t\t\t\tvar hdr [4]byte\n\t\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)","numLines":100,"startLine":125,"totalLines":982}},"sourceToolAssistantUUID":"6b40151a-90ea-43cc-a426-fab93e2e4319","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"588525d6-4d3f-49c3-8b7e-f07c50e4dcc8","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CXGfsb5WqL8iSNihWTQFVN","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01Q2TArzMotZoPuhtVbvxwmi","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","limit":120,"offset":640},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":4071,"cache_read_input_tokens":26715,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":4071},"output_tokens":23,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX76a5antaHx7rUY5XAx","type":"assistant","uuid":"caf53159-4069-4276-be8c-b593c72f64e8","timestamp":"2026-03-29T09:06:31.020Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"caf53159-4069-4276-be8c-b593c72f64e8","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01Q2TArzMotZoPuhtVbvxwmi","type":"tool_result","content":"640\t}\n641\t\n642\t// joinSelector builds a cache key from a selector slice using null bytes as separators.\n643\tfunc joinSelector(sel []string) string {\n644\t\tif len(sel) == 0 {\n645\t\t\treturn \"\"\n646\t\t}\n647\t\tvar result strings.Builder\n648\t\tresult.WriteString(sel[0])\n649\t\tfor i := 1; i < len(sel); i++ {\n650\t\t\tresult.WriteString(\"\\x00\" + sel[i])\n651\t\t}\n652\t\treturn result.String()\n653\t}\n654\t\n655\t// ToCheckpointWAL writes binary snapshot files for all hosts in parallel.\n656\t// Returns the number of files written, the list of host directories that were\n657\t// successfully checkpointed (for WAL rotation), and any errors.\n658\tfunc (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string, error) {\n659\t\t// Collect all cluster/host pairs.\n660\t\tm.root.lock.RLock()\n661\t\ttotalHosts := 0\n662\t\tfor _, l1 := range m.root.children {\n663\t\t\tl1.lock.RLock()\n664\t\t\ttotalHosts += len(l1.children)\n665\t\t\tl1.lock.RUnlock()\n666\t\t}\n667\t\tm.root.lock.RUnlock()\n668\t\n669\t\tlevels := make([]*Level, 0, totalHosts)\n670\t\tselectors := make([][]string, 0, totalHosts)\n671\t\n672\t\tm.root.lock.RLock()\n673\t\tfor sel1, l1 := range m.root.children {\n674\t\t\tl1.lock.RLock()\n675\t\t\tfor sel2, l2 := range l1.children {\n676\t\t\t\tlevels = append(levels, l2)\n677\t\t\t\tselectors = append(selectors, []string{sel1, sel2})\n678\t\t\t}\n679\t\t\tl1.lock.RUnlock()\n680\t\t}\n681\t\tm.root.lock.RUnlock()\n682\t\n683\t\ttype workItem struct {\n684\t\t\tlevel *Level\n685\t\t\thostDir string\n686\t\t\tselector []string\n687\t\t}\n688\t\n689\t\ttotalWork := len(levels)\n690\t\tcclog.Infof(\"[METRICSTORE]> Starting binary checkpoint for %d hosts with %d workers\", totalWork, Keys.NumWorkers)\n691\t\n692\t\tn, errs, completed := int32(0), int32(0), int32(0)\n693\t\tvar successDirs []string\n694\t\tvar successMu sync.Mutex\n695\t\n696\t\tvar wg sync.WaitGroup\n697\t\twg.Add(Keys.NumWorkers)\n698\t\twork := make(chan workItem, Keys.NumWorkers*2)\n699\t\n700\t\t// Progress logging goroutine.\n701\t\tstopProgress := make(chan struct{})\n702\t\tgo func() {\n703\t\t\tticker := time.NewTicker(10 * time.Second)\n704\t\t\tdefer ticker.Stop()\n705\t\t\tfor {\n706\t\t\t\tselect {\n707\t\t\t\tcase <-ticker.C:\n708\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> Checkpoint progress: %d/%d hosts (%d written, %d errors)\",\n709\t\t\t\t\t\tatomic.LoadInt32(&completed), totalWork, atomic.LoadInt32(&n), atomic.LoadInt32(&errs))\n710\t\t\t\tcase <-stopProgress:\n711\t\t\t\t\treturn\n712\t\t\t\t}\n713\t\t\t}\n714\t\t}()\n715\t\n716\t\tfor range Keys.NumWorkers {\n717\t\t\tgo func() {\n718\t\t\t\tdefer wg.Done()\n719\t\t\t\tfor wi := range work {\n720\t\t\t\t\terr := wi.level.toCheckpointBinary(wi.hostDir, from, to, m)\n721\t\t\t\t\tif err != nil {\n722\t\t\t\t\t\tif err == ErrNoNewArchiveData {\n723\t\t\t\t\t\t\tatomic.AddInt32(&completed, 1)\n724\t\t\t\t\t\t\tcontinue\n725\t\t\t\t\t\t}\n726\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpoint error for %s: %v\", wi.hostDir, err)\n727\t\t\t\t\t\tatomic.AddInt32(&errs, 1)\n728\t\t\t\t\t} else {\n729\t\t\t\t\t\tatomic.AddInt32(&n, 1)\n730\t\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n731\t\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n732\t\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n733\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n734\t\t\t\t\t\t}\n735\t\t\t\t\t\tsuccessMu.Lock()\n736\t\t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n737\t\t\t\t\t\tsuccessMu.Unlock()\n738\t\t\t\t\t}\n739\t\t\t\t\tatomic.AddInt32(&completed, 1)\n740\t\t\t\t}\n741\t\t\t}()\n742\t\t}\n743\t\n744\t\tfor i := range levels {\n745\t\t\thostDir := path.Join(dir, path.Join(selectors[i]...))\n746\t\t\twork <- workItem{\n747\t\t\t\tlevel: levels[i],\n748\t\t\t\thostDir: hostDir,\n749\t\t\t\tselector: selectors[i],\n750\t\t\t}\n751\t\t}\n752\t\tclose(work)\n753\t\twg.Wait()\n754\t\tclose(stopProgress)\n755\t\n756\t\tif errs > 0 {\n757\t\t\treturn int(n), successDirs, fmt.Errorf(\"[METRICSTORE]> %d errors during binary checkpoint (%d successes)\", errs, n)\n758\t\t}\n759\t\treturn int(n), successDirs, nil"}]},"uuid":"46f374ed-a3db-4ec7-97d1-c36ede0dfd9d","timestamp":"2026-03-29T09:06:31.027Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"}\n\n// joinSelector builds a cache key from a selector slice using null bytes as separators.\nfunc joinSelector(sel []string) string {\n\tif len(sel) == 0 {\n\t\treturn \"\"\n\t}\n\tvar result strings.Builder\n\tresult.WriteString(sel[0])\n\tfor i := 1; i < len(sel); i++ {\n\t\tresult.WriteString(\"\\x00\" + sel[i])\n\t}\n\treturn result.String()\n}\n\n// ToCheckpointWAL writes binary snapshot files for all hosts in parallel.\n// Returns the number of files written, the list of host directories that were\n// successfully checkpointed (for WAL rotation), and any errors.\nfunc (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string, error) {\n\t// Collect all cluster/host pairs.\n\tm.root.lock.RLock()\n\ttotalHosts := 0\n\tfor _, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\ttotalHosts += len(l1.children)\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\tlevels := make([]*Level, 0, totalHosts)\n\tselectors := make([][]string, 0, totalHosts)\n\n\tm.root.lock.RLock()\n\tfor sel1, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\tfor sel2, l2 := range l1.children {\n\t\t\tlevels = append(levels, l2)\n\t\t\tselectors = append(selectors, []string{sel1, sel2})\n\t\t}\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\ttype workItem struct {\n\t\tlevel *Level\n\t\thostDir string\n\t\tselector []string\n\t}\n\n\ttotalWork := len(levels)\n\tcclog.Infof(\"[METRICSTORE]> Starting binary checkpoint for %d hosts with %d workers\", totalWork, Keys.NumWorkers)\n\n\tn, errs, completed := int32(0), int32(0), int32(0)\n\tvar successDirs []string\n\tvar successMu sync.Mutex\n\n\tvar wg sync.WaitGroup\n\twg.Add(Keys.NumWorkers)\n\twork := make(chan workItem, Keys.NumWorkers*2)\n\n\t// Progress logging goroutine.\n\tstopProgress := make(chan struct{})\n\tgo func() {\n\t\tticker := time.NewTicker(10 * time.Second)\n\t\tdefer ticker.Stop()\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ticker.C:\n\t\t\t\tcclog.Infof(\"[METRICSTORE]> Checkpoint progress: %d/%d hosts (%d written, %d errors)\",\n\t\t\t\t\tatomic.LoadInt32(&completed), totalWork, atomic.LoadInt32(&n), atomic.LoadInt32(&errs))\n\t\t\tcase <-stopProgress:\n\t\t\t\treturn\n\t\t\t}\n\t\t}\n\t}()\n\n\tfor range Keys.NumWorkers {\n\t\tgo func() {\n\t\t\tdefer wg.Done()\n\t\t\tfor wi := range work {\n\t\t\t\terr := wi.level.toCheckpointBinary(wi.hostDir, from, to, m)\n\t\t\t\tif err != nil {\n\t\t\t\t\tif err == ErrNoNewArchiveData {\n\t\t\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t\t\t\tcontinue\n\t\t\t\t\t}\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpoint error for %s: %v\", wi.hostDir, err)\n\t\t\t\t\tatomic.AddInt32(&errs, 1)\n\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tsuccessMu.Lock()\n\t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n\t\t\t\t\tsuccessMu.Unlock()\n\t\t\t\t}\n\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t}\n\t\t}()\n\t}\n\n\tfor i := range levels {\n\t\thostDir := path.Join(dir, path.Join(selectors[i]...))\n\t\twork <- workItem{\n\t\t\tlevel: levels[i],\n\t\t\thostDir: hostDir,\n\t\t\tselector: selectors[i],\n\t\t}\n\t}\n\tclose(work)\n\twg.Wait()\n\tclose(stopProgress)\n\n\tif errs > 0 {\n\t\treturn int(n), successDirs, fmt.Errorf(\"[METRICSTORE]> %d errors during binary checkpoint (%d successes)\", errs, n)\n\t}\n\treturn int(n), successDirs, nil","numLines":120,"startLine":640,"totalLines":982}},"sourceToolAssistantUUID":"caf53159-4069-4276-be8c-b593c72f64e8","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"46f374ed-a3db-4ec7-97d1-c36ede0dfd9d","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CXGfsb5WqL8iSNihWTQFVN","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01H6mcEKC1xus6hPWcAYryUE","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/lineprotocol.go","limit":60,"offset":330},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":4071,"cache_read_input_tokens":26715,"output_tokens":366,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":4071,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX76a5antaHx7rUY5XAx","type":"assistant","uuid":"a84b6cb8-ab9c-4dd2-b505-cde51dc4c3ab","timestamp":"2026-03-29T09:06:31.678Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"a84b6cb8-ab9c-4dd2-b505-cde51dc4c3ab","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01H6mcEKC1xus6hPWcAYryUE","type":"tool_result","content":"330\t\t\t\t\tmetric.Value = schema.Float(val.UintV())\n331\t\t\t\t} else {\n332\t\t\t\t\treturn fmt.Errorf(\"host %s: unsupported value type in message: %s\", host, val.Kind().String())\n333\t\t\t\t}\n334\t\t\t}\n335\t\n336\t\t\tif t, err = dec.Time(lineprotocol.Second, t); err != nil {\n337\t\t\t\tt = time.Now()\n338\t\t\t\tif t, err = dec.Time(lineprotocol.Millisecond, t); err != nil {\n339\t\t\t\t\tt = time.Now()\n340\t\t\t\t\tif t, err = dec.Time(lineprotocol.Microsecond, t); err != nil {\n341\t\t\t\t\t\tt = time.Now()\n342\t\t\t\t\t\tif t, err = dec.Time(lineprotocol.Nanosecond, t); err != nil {\n343\t\t\t\t\t\t\treturn fmt.Errorf(\"host %s: timestamp : %#v with error : %#v\", host, t, err.Error())\n344\t\t\t\t\t\t}\n345\t\t\t\t\t}\n346\t\t\t\t}\n347\t\t\t}\n348\t\n349\t\t\tif err != nil {\n350\t\t\t\treturn fmt.Errorf(\"host %s: timestamp : %#v with error : %#v\", host, t, err.Error())\n351\t\t\t}\n352\t\n353\t\t\ttime := t.Unix()\n354\t\n355\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n356\t\t\t\tmsg := &WALMessage{\n357\t\t\t\t\tMetricName: string(st.metricBuf),\n358\t\t\t\t\tCluster: cluster,\n359\t\t\t\t\tNode: host,\n360\t\t\t\t\tSelector: append([]string{}, st.selector...),\n361\t\t\t\t\tValue: metric.Value,\n362\t\t\t\t\tTimestamp: time,\n363\t\t\t\t}\n364\t\t\t\tif !SendWALMessage(msg) {\n365\t\t\t\t\t// WAL shard channel full — metric is written to memory store but not WAL.\n366\t\t\t\t\t// Next binary snapshot will capture it.\n367\t\t\t\t\tif dropped := walDropped.Add(1); dropped%10000 == 1 {\n368\t\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL shard channel full, dropped %d messages (data safe in memory, next snapshot will capture)\", dropped)\n369\t\t\t\t\t}\n370\t\t\t\t}\n371\t\t\t}\n372\t\n373\t\t\tif err := ms.WriteToLevel(lvl, st.selector, time, []Metric{metric}); err != nil {\n374\t\t\t\tcclog.Warnf(\"write error for host %s metric %s at ts %d: %s\", host, string(st.metricBuf), time, err.Error())\n375\t\t\t\tcontinue\n376\t\t\t}\n377\t\t}\n378\t\treturn nil\n379\t}\n380\t"}]},"uuid":"0706ab42-6ca8-4add-afb0-198a2f773531","timestamp":"2026-03-29T09:06:31.692Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/lineprotocol.go","content":"\t\t\t\tmetric.Value = schema.Float(val.UintV())\n\t\t\t} else {\n\t\t\t\treturn fmt.Errorf(\"host %s: unsupported value type in message: %s\", host, val.Kind().String())\n\t\t\t}\n\t\t}\n\n\t\tif t, err = dec.Time(lineprotocol.Second, t); err != nil {\n\t\t\tt = time.Now()\n\t\t\tif t, err = dec.Time(lineprotocol.Millisecond, t); err != nil {\n\t\t\t\tt = time.Now()\n\t\t\t\tif t, err = dec.Time(lineprotocol.Microsecond, t); err != nil {\n\t\t\t\t\tt = time.Now()\n\t\t\t\t\tif t, err = dec.Time(lineprotocol.Nanosecond, t); err != nil {\n\t\t\t\t\t\treturn fmt.Errorf(\"host %s: timestamp : %#v with error : %#v\", host, t, err.Error())\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tif err != nil {\n\t\t\treturn fmt.Errorf(\"host %s: timestamp : %#v with error : %#v\", host, t, err.Error())\n\t\t}\n\n\t\ttime := t.Unix()\n\n\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n\t\t\tmsg := &WALMessage{\n\t\t\t\tMetricName: string(st.metricBuf),\n\t\t\t\tCluster: cluster,\n\t\t\t\tNode: host,\n\t\t\t\tSelector: append([]string{}, st.selector...),\n\t\t\t\tValue: metric.Value,\n\t\t\t\tTimestamp: time,\n\t\t\t}\n\t\t\tif !SendWALMessage(msg) {\n\t\t\t\t// WAL shard channel full — metric is written to memory store but not WAL.\n\t\t\t\t// Next binary snapshot will capture it.\n\t\t\t\tif dropped := walDropped.Add(1); dropped%10000 == 1 {\n\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL shard channel full, dropped %d messages (data safe in memory, next snapshot will capture)\", dropped)\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tif err := ms.WriteToLevel(lvl, st.selector, time, []Metric{metric}); err != nil {\n\t\t\tcclog.Warnf(\"write error for host %s metric %s at ts %d: %s\", host, string(st.metricBuf), time, err.Error())\n\t\t\tcontinue\n\t\t}\n\t}\n\treturn nil\n}\n","numLines":51,"startLine":330,"totalLines":380}},"sourceToolAssistantUUID":"a84b6cb8-ab9c-4dd2-b505-cde51dc4c3ab","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"0706ab42-6ca8-4add-afb0-198a2f773531","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01VgwAfbfHX2uhUykjZbFxp7","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01AtqK6aoWjdVrdqmYMziTqJ","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","limit":80,"offset":760},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3679,"cache_read_input_tokens":30786,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":3679},"output_tokens":59,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX772vNUR5eDNyFtu6ry","type":"assistant","uuid":"b29131c1-89ad-43fc-847e-cbf20aaa3d56","timestamp":"2026-03-29T09:06:36.079Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"b29131c1-89ad-43fc-847e-cbf20aaa3d56","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01AtqK6aoWjdVrdqmYMziTqJ","type":"tool_result","content":"760\t}\n761\t\n762\t// toCheckpointBinary writes a binary snapshot file for a single host-level node.\n763\t// Uses atomic rename (write to .tmp then rename) to avoid partial reads on crash.\n764\tfunc (l *Level) toCheckpointBinary(dir string, from, to int64, m *MemoryStore) error {\n765\t\tcf, err := l.toCheckpointFile(from, to, m)\n766\t\tif err != nil {\n767\t\t\treturn err\n768\t\t}\n769\t\tif cf == nil {\n770\t\t\treturn ErrNoNewArchiveData\n771\t\t}\n772\t\n773\t\tif err := os.MkdirAll(dir, CheckpointDirPerms); err != nil {\n774\t\t\treturn fmt.Errorf(\"mkdir %s: %w\", dir, err)\n775\t\t}\n776\t\n777\t\t// Write to a temp file first, then rename (atomic on POSIX).\n778\t\ttmpPath := path.Join(dir, fmt.Sprintf(\"%d.bin.tmp\", from))\n779\t\tfinalPath := path.Join(dir, fmt.Sprintf(\"%d.bin\", from))\n780\t\n781\t\tf, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n782\t\tif err != nil {\n783\t\t\treturn fmt.Errorf(\"open binary snapshot %s: %w\", tmpPath, err)\n784\t\t}\n785\t\n786\t\tbw := bufio.NewWriter(f)\n787\t\tif err := writeBinarySnapshotFile(bw, cf); err != nil {\n788\t\t\tf.Close()\n789\t\t\tos.Remove(tmpPath)\n790\t\t\treturn fmt.Errorf(\"write binary snapshot: %w\", err)\n791\t\t}\n792\t\tif err := bw.Flush(); err != nil {\n793\t\t\tf.Close()\n794\t\t\tos.Remove(tmpPath)\n795\t\t\treturn err\n796\t\t}\n797\t\tf.Close()\n798\t\n799\t\treturn os.Rename(tmpPath, finalPath)\n800\t}\n801\t\n802\t// writeBinarySnapshotFile writes the binary snapshot file header and level tree.\n803\tfunc writeBinarySnapshotFile(w io.Writer, cf *CheckpointFile) error {\n804\t\tif err := binary.Write(w, binary.LittleEndian, snapFileMagic); err != nil {\n805\t\t\treturn err\n806\t\t}\n807\t\tif err := binary.Write(w, binary.LittleEndian, cf.From); err != nil {\n808\t\t\treturn err\n809\t\t}\n810\t\tif err := binary.Write(w, binary.LittleEndian, cf.To); err != nil {\n811\t\t\treturn err\n812\t\t}\n813\t\treturn writeBinaryLevel(w, cf)\n814\t}\n815\t\n816\t// writeBinaryLevel recursively writes a CheckpointFile level in binary format.\n817\tfunc writeBinaryLevel(w io.Writer, cf *CheckpointFile) error {\n818\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Metrics))); err != nil {\n819\t\t\treturn err\n820\t\t}\n821\t\n822\t\tfor name, metric := range cf.Metrics {\n823\t\t\tif err := writeString16(w, name); err != nil {\n824\t\t\t\treturn err\n825\t\t\t}\n826\t\t\tif err := binary.Write(w, binary.LittleEndian, metric.Frequency); err != nil {\n827\t\t\t\treturn err\n828\t\t\t}\n829\t\t\tif err := binary.Write(w, binary.LittleEndian, metric.Start); err != nil {\n830\t\t\t\treturn err\n831\t\t\t}\n832\t\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(metric.Data))); err != nil {\n833\t\t\t\treturn err\n834\t\t\t}\n835\t\t\tfor _, v := range metric.Data {\n836\t\t\t\tif err := binary.Write(w, binary.LittleEndian, math.Float32bits(float32(v))); err != nil {\n837\t\t\t\t\treturn err\n838\t\t\t\t}\n839\t\t\t}"}]},"uuid":"54605232-d36f-4464-af64-6717d11c2f2b","timestamp":"2026-03-29T09:06:36.087Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"}\n\n// toCheckpointBinary writes a binary snapshot file for a single host-level node.\n// Uses atomic rename (write to .tmp then rename) to avoid partial reads on crash.\nfunc (l *Level) toCheckpointBinary(dir string, from, to int64, m *MemoryStore) error {\n\tcf, err := l.toCheckpointFile(from, to, m)\n\tif err != nil {\n\t\treturn err\n\t}\n\tif cf == nil {\n\t\treturn ErrNoNewArchiveData\n\t}\n\n\tif err := os.MkdirAll(dir, CheckpointDirPerms); err != nil {\n\t\treturn fmt.Errorf(\"mkdir %s: %w\", dir, err)\n\t}\n\n\t// Write to a temp file first, then rename (atomic on POSIX).\n\ttmpPath := path.Join(dir, fmt.Sprintf(\"%d.bin.tmp\", from))\n\tfinalPath := path.Join(dir, fmt.Sprintf(\"%d.bin\", from))\n\n\tf, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"open binary snapshot %s: %w\", tmpPath, err)\n\t}\n\n\tbw := bufio.NewWriter(f)\n\tif err := writeBinarySnapshotFile(bw, cf); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn fmt.Errorf(\"write binary snapshot: %w\", err)\n\t}\n\tif err := bw.Flush(); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn err\n\t}\n\tf.Close()\n\n\treturn os.Rename(tmpPath, finalPath)\n}\n\n// writeBinarySnapshotFile writes the binary snapshot file header and level tree.\nfunc writeBinarySnapshotFile(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, snapFileMagic); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.From); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.To); err != nil {\n\t\treturn err\n\t}\n\treturn writeBinaryLevel(w, cf)\n}\n\n// writeBinaryLevel recursively writes a CheckpointFile level in binary format.\nfunc writeBinaryLevel(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Metrics))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, metric := range cf.Metrics {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Frequency); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Start); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(metric.Data))); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tfor _, v := range metric.Data {\n\t\t\tif err := binary.Write(w, binary.LittleEndian, math.Float32bits(float32(v))); err != nil {\n\t\t\t\treturn err\n\t\t\t}\n\t\t}","numLines":80,"startLine":760,"totalLines":982}},"sourceToolAssistantUUID":"b29131c1-89ad-43fc-847e-cbf20aaa3d56","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} 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{"parentUuid":"fadb0a07-8d5f-4009-a714-0c45ee27c6e3","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01VwxJZchJtEBr4t6iGMfG12","type":"tool_result","content":"255\t\n256\t\tif errs > 0 {\n257\t\t\treturn int(n), fmt.Errorf(\"[METRICSTORE]> %d errors happened while creating checkpoints (%d successes)\", errs, n)\n258\t\t}\n259\t\treturn int(n), nil\n260\t}\n261\t\n262\t// toCheckpointFile recursively converts a Level tree to CheckpointFile structure.\n263\t// Skips metrics that are already archived. Returns nil if no unarchived data exists.\n264\tfunc (l *Level) toCheckpointFile(from, to int64, m *MemoryStore) (*CheckpointFile, error) {\n265\t\tl.lock.RLock()\n266\t\tdefer l.lock.RUnlock()\n267\t\n268\t\tretval := &CheckpointFile{\n269\t\t\tFrom: from,\n270\t\t\tTo: to,\n271\t\t\tMetrics: make(map[string]*CheckpointMetrics),\n272\t\t\tChildren: make(map[string]*CheckpointFile),\n273\t\t}\n274\t\n275\t\tfor metric, minfo := range m.Metrics {\n276\t\t\tb := l.metrics[minfo.offset]\n277\t\t\tif b == nil {\n278\t\t\t\tcontinue\n279\t\t\t}\n280\t\n281\t\t\tallArchived := true\n282\t\t\tb.iterFromTo(from, to, func(b *buffer) error {\n283\t\t\t\tif !b.archived {\n284\t\t\t\t\tallArchived = false\n285\t\t\t\t\treturn fmt.Errorf(\"stop\") // Early termination signal\n286\t\t\t\t}\n287\t\t\t\treturn nil\n288\t\t\t})\n289\t\n290\t\t\tif allArchived {\n291\t\t\t\tcontinue\n292\t\t\t}\n293\t\n294\t\t\tdata := make([]schema.Float, (to-from)/b.frequency+1)\n295\t\t\tdata, start, end, err := b.read(from, to, data)\n296\t\t\tif err != nil {\n297\t\t\t\treturn nil, err\n298\t\t\t}\n299\t\n300\t\t\tfor i := int((end - start) / b.frequency); i < len(data); i++ {\n301\t\t\t\tdata[i] = schema.NaN\n302\t\t\t}\n303\t\n304\t\t\tretval.Metrics[metric] = &CheckpointMetrics{\n305\t\t\t\tFrequency: b.frequency,\n306\t\t\t\tStart: start,\n307\t\t\t\tData: data,\n308\t\t\t}\n309\t\t}\n310\t\n311\t\tfor name, child := range l.children {\n312\t\t\tval, err := child.toCheckpointFile(from, to, m)\n313\t\t\tif err != nil {\n314\t\t\t\treturn nil, err\n315\t\t\t}\n316\t\n317\t\t\tif val != nil {\n318\t\t\t\tretval.Children[name] = val\n319\t\t\t}\n320\t\t}\n321\t\n322\t\tif len(retval.Children) == 0 && len(retval.Metrics) == 0 {\n323\t\t\treturn nil, nil\n324\t\t}\n325\t\n326\t\treturn retval, nil\n327\t}\n328\t\n329\t// toCheckpoint writes a Level's data to a JSON checkpoint file.\n330\t// Creates directory if needed. Returns ErrNoNewArchiveData if nothing to save.\n331\tfunc (l *Level) toCheckpoint(dir string, from, to int64, m *MemoryStore) error {\n332\t\tcf, err := l.toCheckpointFile(from, to, m)\n333\t\tif err != nil {\n334\t\t\treturn err"}]},"uuid":"2532334c-4e29-486f-8050-dea7d4d20901","timestamp":"2026-03-29T09:06:36.532Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go","content":"\n\tif errs > 0 {\n\t\treturn int(n), fmt.Errorf(\"[METRICSTORE]> %d errors happened while creating checkpoints (%d successes)\", errs, n)\n\t}\n\treturn int(n), nil\n}\n\n// toCheckpointFile recursively converts a Level tree to CheckpointFile structure.\n// Skips metrics that are already archived. Returns nil if no unarchived data exists.\nfunc (l *Level) toCheckpointFile(from, to int64, m *MemoryStore) (*CheckpointFile, error) {\n\tl.lock.RLock()\n\tdefer l.lock.RUnlock()\n\n\tretval := &CheckpointFile{\n\t\tFrom: from,\n\t\tTo: to,\n\t\tMetrics: make(map[string]*CheckpointMetrics),\n\t\tChildren: make(map[string]*CheckpointFile),\n\t}\n\n\tfor metric, minfo := range m.Metrics {\n\t\tb := l.metrics[minfo.offset]\n\t\tif b == nil {\n\t\t\tcontinue\n\t\t}\n\n\t\tallArchived := true\n\t\tb.iterFromTo(from, to, func(b *buffer) error {\n\t\t\tif !b.archived {\n\t\t\t\tallArchived = false\n\t\t\t\treturn fmt.Errorf(\"stop\") // Early termination signal\n\t\t\t}\n\t\t\treturn nil\n\t\t})\n\n\t\tif allArchived {\n\t\t\tcontinue\n\t\t}\n\n\t\tdata := make([]schema.Float, (to-from)/b.frequency+1)\n\t\tdata, start, end, err := b.read(from, to, data)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\n\t\tfor i := int((end - start) / b.frequency); i < len(data); i++ {\n\t\t\tdata[i] = schema.NaN\n\t\t}\n\n\t\tretval.Metrics[metric] = &CheckpointMetrics{\n\t\t\tFrequency: b.frequency,\n\t\t\tStart: start,\n\t\t\tData: data,\n\t\t}\n\t}\n\n\tfor name, child := range l.children {\n\t\tval, err := child.toCheckpointFile(from, to, m)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\n\t\tif val != nil {\n\t\t\tretval.Children[name] = val\n\t\t}\n\t}\n\n\tif len(retval.Children) == 0 && len(retval.Metrics) == 0 {\n\t\treturn nil, nil\n\t}\n\n\treturn retval, nil\n}\n\n// toCheckpoint writes a Level's data to a JSON checkpoint file.\n// Creates directory if needed. Returns ErrNoNewArchiveData if nothing to save.\nfunc (l *Level) toCheckpoint(dir string, from, to int64, m *MemoryStore) error {\n\tcf, err := l.toCheckpointFile(from, to, m)\n\tif err != nil {\n\t\treturn err","numLines":80,"startLine":255,"totalLines":671}},"sourceToolAssistantUUID":"fadb0a07-8d5f-4009-a714-0c45ee27c6e3","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} 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{"parentUuid":"cc63b8dd-4170-4ea6-a53a-a86c952d9bb5","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01L3939TsCQyvgGrh2w1bYTm","type":"tool_result","content":"225\t\t\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n226\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n227\t\t\t\t\t\t\tf.Close()\n228\t\t\t\t\t\t\treturn nil\n229\t\t\t\t\t\t}\n230\t\t\t\t\t\tfileSize = 4\n231\t\t\t\t\t}\n232\t\n233\t\t\t\t\tws = &walFileState{f: f, w: w, size: fileSize}\n234\t\t\t\t\thostFiles[hostDir] = ws\n235\t\t\t\t\treturn ws\n236\t\t\t\t}\n237\t\n238\t\t\t\tprocessMsg := func(msg *WALMessage) {\n239\t\t\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n240\t\t\t\t\tws := getOrOpenWAL(hostDir)\n241\t\t\t\t\tif ws == nil {\n242\t\t\t\t\t\treturn\n243\t\t\t\t\t}\n244\t\n245\t\t\t\t\t// Enforce max WAL size: force-rotate before writing if limit is exceeded.\n246\t\t\t\t\t// The in-memory store still holds the data; only crash-recovery coverage is lost.\n247\t\t\t\t\tif maxSize := Keys.Checkpoints.MaxWALSize; maxSize > 0 && ws.size >= maxSize {\n248\t\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL: force-rotating %s (size %d >= limit %d)\",\n249\t\t\t\t\t\t\thostDir, ws.size, maxSize)\n250\t\t\t\t\t\tws.w.Flush()\n251\t\t\t\t\t\tws.f.Close()\n252\t\t\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n253\t\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n254\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n255\t\t\t\t\t\t}\n256\t\t\t\t\t\tdelete(hostFiles, hostDir)\n257\t\t\t\t\t\tws = getOrOpenWAL(hostDir)\n258\t\t\t\t\t\tif ws == nil {\n259\t\t\t\t\t\t\treturn\n260\t\t\t\t\t\t}\n261\t\t\t\t\t}\n262\t\n263\t\t\t\t\tn, err := writeWALRecordDirect(ws.w, msg)\n264\t\t\t\t\tif err != nil {\n265\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n266\t\t\t\t\t}\n267\t\t\t\t\tws.size += int64(n)\n268\t\t\t\t\tws.dirty = true\n269\t\t\t\t}\n270\t\n271\t\t\t\tprocessRotate := func(req walRotateReq) {\n272\t\t\t\t\tws, ok := hostFiles[req.hostDir]\n273\t\t\t\t\tif ok && ws.f != nil {\n274\t\t\t\t\t\tws.w.Flush()\n275\t\t\t\t\t\tws.f.Close()\n276\t\t\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n277\t\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n278\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n279\t\t\t\t\t\t}\n280\t\t\t\t\t\tdelete(hostFiles, req.hostDir)\n281\t\t\t\t\t}\n282\t\t\t\t\tclose(req.done)\n283\t\t\t\t}\n284\t\n285\t\t\t\tflushDirty := func() {\n286\t\t\t\t\tfor _, ws := range hostFiles {\n287\t\t\t\t\t\tif ws.dirty {\n288\t\t\t\t\t\t\tws.w.Flush()\n289\t\t\t\t\t\t\tws.dirty = false\n290\t\t\t\t\t\t}\n291\t\t\t\t\t}\n292\t\t\t\t}\n293\t\n294\t\t\t\tticker := time.NewTicker(walFlushInterval)\n295\t\t\t\tdefer ticker.Stop()\n296\t\n297\t\t\t\t// drainBatch processes up to 4096 pending messages without blocking.\n298\t\t\t\t// Returns false if the channel was closed.\n299\t\t\t\tdrainBatch := func() bool {\n300\t\t\t\t\tfor range 4096 {\n301\t\t\t\t\t\tselect {\n302\t\t\t\t\t\tcase msg, ok := <-msgCh:\n303\t\t\t\t\t\t\tif !ok {\n304\t\t\t\t\t\t\t\tflushDirty()\n305\t\t\t\t\t\t\t\treturn false\n306\t\t\t\t\t\t\t}\n307\t\t\t\t\t\t\tprocessMsg(msg)\n308\t\t\t\t\t\tcase req := <-rotateCh:\n309\t\t\t\t\t\t\tprocessRotate(req)\n310\t\t\t\t\t\tdefault:\n311\t\t\t\t\t\t\treturn true\n312\t\t\t\t\t\t}\n313\t\t\t\t\t}\n314\t\t\t\t\treturn true\n315\t\t\t\t}\n316\t\n317\t\t\t\tfor {\n318\t\t\t\t\tselect {\n319\t\t\t\t\tcase <-ctx.Done():\n320\t\t\t\t\t\t// On shutdown, skip draining buffered messages — a full binary\n321\t\t\t\t\t\t// checkpoint will be written from in-memory state, making\n322\t\t\t\t\t\t// buffered WAL records redundant.\n323\t\t\t\t\t\tflushDirty()\n324\t\t\t\t\t\treturn\n325\t\t\t\t\tcase msg, ok := <-msgCh:\n326\t\t\t\t\t\tif !ok {\n327\t\t\t\t\t\t\treturn\n328\t\t\t\t\t\t}\n329\t\t\t\t\t\tprocessMsg(msg)\n330\t\t\t\t\t\tif !drainBatch() {\n331\t\t\t\t\t\t\treturn\n332\t\t\t\t\t\t}\n333\t\t\t\t\t\t// No flush here — timer handles periodic flushing.\n334\t\t\t\t\tcase <-ticker.C:\n335\t\t\t\t\t\tflushDirty()\n336\t\t\t\t\tcase req := <-rotateCh:\n337\t\t\t\t\t\tprocessRotate(req)\n338\t\t\t\t\t}\n339\t\t\t\t}\n340\t\t\t})\n341\t\t}\n342\t}\n343\t\n344\t// WaitForWALStagingDrain blocks until all WALStaging goroutines have exited.\n345\t// Must be called after closing walShardChs to ensure all file handles are\n346\t// flushed and closed before checkpoint writes begin.\n347\tfunc WaitForWALStagingDrain() {\n348\t\twalStagingWg.Wait()\n349\t}\n350\t\n351\t// RotateWALFiles sends rotation requests for the given host directories\n352\t// and blocks until all rotations complete. Each request is routed to the\n353\t// shard that owns the host directory.\n354\t//"}]},"uuid":"bfa0ad34-3307-47f0-bd95-db77181608dc","timestamp":"2026-03-29T09:07:07.969Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"\t\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\t\tf.Close()\n\t\t\t\t\t\treturn nil\n\t\t\t\t\t}\n\t\t\t\t\tfileSize = 4\n\t\t\t\t}\n\n\t\t\t\tws = &walFileState{f: f, w: w, size: fileSize}\n\t\t\t\thostFiles[hostDir] = ws\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\t\tif ws == nil {\n\t\t\t\t\treturn\n\t\t\t\t}\n\n\t\t\t\t// Enforce max WAL size: force-rotate before writing if limit is exceeded.\n\t\t\t\t// The in-memory store still holds the data; only crash-recovery coverage is lost.\n\t\t\t\tif maxSize := Keys.Checkpoints.MaxWALSize; maxSize > 0 && ws.size >= maxSize {\n\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL: force-rotating %s (size %d >= limit %d)\",\n\t\t\t\t\t\thostDir, ws.size, maxSize)\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, hostDir)\n\t\t\t\t\tws = getOrOpenWAL(hostDir)\n\t\t\t\t\tif ws == nil {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t}\n\n\t\t\t\tn, err := writeWALRecordDirect(ws.w, msg)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t\t}\n\t\t\t\tws.size += int64(n)\n\t\t\t\tws.dirty = true\n\t\t\t}\n\n\t\t\tprocessRotate := func(req walRotateReq) {\n\t\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\t\tif ok && ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t\t}\n\t\t\t\tclose(req.done)\n\t\t\t}\n\n\t\t\tflushDirty := func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.dirty {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.dirty = false\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tticker := time.NewTicker(walFlushInterval)\n\t\t\tdefer ticker.Stop()\n\n\t\t\t// drainBatch processes up to 4096 pending messages without blocking.\n\t\t\t// Returns false if the channel was closed.\n\t\t\tdrainBatch := func() bool {\n\t\t\t\tfor range 4096 {\n\t\t\t\t\tselect {\n\t\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\t\tif !ok {\n\t\t\t\t\t\t\tflushDirty()\n\t\t\t\t\t\t\treturn false\n\t\t\t\t\t\t}\n\t\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\t\tprocessRotate(req)\n\t\t\t\t\tdefault:\n\t\t\t\t\t\treturn true\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\treturn true\n\t\t\t}\n\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase <-ctx.Done():\n\t\t\t\t\t// On shutdown, skip draining buffered messages — a full binary\n\t\t\t\t\t// checkpoint will be written from in-memory state, making\n\t\t\t\t\t// buffered WAL records redundant.\n\t\t\t\t\tflushDirty()\n\t\t\t\t\treturn\n\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\tif !ok {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tif !drainBatch() {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\t// No flush here — timer handles periodic flushing.\n\t\t\t\tcase <-ticker.C:\n\t\t\t\t\tflushDirty()\n\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\t}\n\t\t\t}\n\t\t})\n\t}\n}\n\n// WaitForWALStagingDrain blocks until all WALStaging goroutines have exited.\n// Must be called after closing walShardChs to ensure all file handles are\n// flushed and closed before checkpoint writes begin.\nfunc WaitForWALStagingDrain() {\n\twalStagingWg.Wait()\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete. 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This file is part of cc-backend.\n3\t// Use of this source code is governed by a MIT-style\n4\t// license that can be found in the LICENSE file.\n5\t\n6\t// Package metricstore provides walCheckpoint.go: WAL-based checkpoint implementation.\n7\t//\n8\t// This replaces the Avro shadow tree with an append-only Write-Ahead Log (WAL)\n9\t// per host, eliminating the extra memory overhead of the AvroStore and providing\n10\t// truly continuous (per-write) crash safety.\n11\t//\n12\t// # Architecture\n13\t//\n14\t//\tMetric write (DecodeLine)\n15\t//\t │\n16\t//\t ├─► WriteToLevel() → main MemoryStore (unchanged)\n17\t//\t │\n18\t//\t └─► WALMessages channel\n19\t//\t │\n20\t//\t ▼\n21\t//\t WALStaging goroutine\n22\t//\t │\n23\t//\t ▼\n24\t//\t checkpoints/cluster/host/current.wal (append-only, binary)\n25\t//\n26\t//\tPeriodic checkpoint (Checkpointing goroutine):\n27\t//\t 1. Write .bin snapshot (column-oriented, from main tree)\n28\t//\t 2. Signal WALStaging to truncate current.wal per host\n29\t//\n30\t//\tOn restart (FromCheckpoint):"}]},"uuid":"d191c3b8-d329-4a04-aa92-57a30c888cbb","timestamp":"2026-03-29T09:07:08.508Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.\n// All rights reserved. This file is part of cc-backend.\n// Use of this source code is governed by a MIT-style\n// license that can be found in the LICENSE file.\n\n// Package metricstore provides walCheckpoint.go: WAL-based checkpoint implementation.\n//\n// This replaces the Avro shadow tree with an append-only Write-Ahead Log (WAL)\n// per host, eliminating the extra memory overhead of the AvroStore and providing\n// truly continuous (per-write) crash safety.\n//\n// # Architecture\n//\n//\tMetric write (DecodeLine)\n//\t │\n//\t ├─► WriteToLevel() → main MemoryStore (unchanged)\n//\t │\n//\t └─► WALMessages channel\n//\t │\n//\t ▼\n//\t WALStaging goroutine\n//\t │\n//\t ▼\n//\t checkpoints/cluster/host/current.wal (append-only, binary)\n//\n//\tPeriodic checkpoint (Checkpointing goroutine):\n//\t 1. Write .bin snapshot (column-oriented, from main tree)\n//\t 2. Signal WALStaging to truncate current.wal per host\n//\n//\tOn restart (FromCheckpoint):","numLines":30,"startLine":1,"totalLines":982}},"sourceToolAssistantUUID":"e8eac6fc-754d-4081-8c07-ee6eeec918be","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} 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{"parentUuid":"65e55d60-7e48-4f64-90e3-cf2b996ce535","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01QokbBLmE9DmTVVSAURqkBZ","type":"message","role":"assistant","content":[{"type":"text","text":"Now let me read the Checkpointing goroutine to see how it calls ToCheckpointWAL and understand the full lifecycle."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3377,"cache_read_input_tokens":36548,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":3377},"output_tokens":28,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX79kUVkQWBEDRF8LWeJ","type":"assistant","uuid":"ebb3d89f-601c-491c-86a5-648d59e9bec7","timestamp":"2026-03-29T09:07:40.360Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"ebb3d89f-601c-491c-86a5-648d59e9bec7","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01QokbBLmE9DmTVVSAURqkBZ","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01K5oZ2CZCUJZhVQgBVtTAdf","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go","limit":80,"offset":130},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3377,"cache_read_input_tokens":36548,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":3377},"output_tokens":28,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX79kUVkQWBEDRF8LWeJ","type":"assistant","uuid":"45c03207-645e-4747-bf96-481fde8e7a33","timestamp":"2026-03-29T09:07:41.263Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"45c03207-645e-4747-bf96-481fde8e7a33","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01K5oZ2CZCUJZhVQgBVtTAdf","type":"tool_result","content":"130\t\t\t\t\t\tif err != nil {\n131\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n132\t\t\t\t\t\t}\n133\t\t\t\t\t\tif n > 0 {\n134\t\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n135\t\t\t\t\t\t\tlastCheckpointMu.Lock()\n136\t\t\t\t\t\t\tlastCheckpoint = now\n137\t\t\t\t\t\t\tlastCheckpointMu.Unlock()\n138\t\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n139\t\t\t\t\t\t\tRotateWALFiles(hostDirs)\n140\t\t\t\t\t\t}\n141\t\t\t\t\t} else {\n142\t\t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n143\t\t\t\t\t\tif err != nil {\n144\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> checkpointing failed: %s\", err.Error())\n145\t\t\t\t\t\t} else {\n146\t\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d checkpoint files created\", n)\n147\t\t\t\t\t\t\tlastCheckpointMu.Lock()\n148\t\t\t\t\t\t\tlastCheckpoint = now\n149\t\t\t\t\t\t\tlastCheckpointMu.Unlock()\n150\t\t\t\t\t\t}\n151\t\t\t\t\t}\n152\t\t\t\t}\n153\t\t\t}\n154\t\t})\n155\t}\n156\t\n157\t// MarshalJSON provides optimized JSON encoding for CheckpointMetrics.\n158\t//\n159\t// Since schema.Float has custom MarshalJSON, serializing []Float has significant overhead.\n160\t// This method manually constructs JSON to avoid allocations and interface conversions.\n161\tfunc (cm *CheckpointMetrics) MarshalJSON() ([]byte, error) {\n162\t\tbuf := make([]byte, 0, 128+len(cm.Data)*8)\n163\t\tbuf = append(buf, `{\"frequency\":`...)\n164\t\tbuf = strconv.AppendInt(buf, cm.Frequency, 10)\n165\t\tbuf = append(buf, `,\"start\":`...)\n166\t\tbuf = strconv.AppendInt(buf, cm.Start, 10)\n167\t\tbuf = append(buf, `,\"data\":[`...)\n168\t\tfor i, x := range cm.Data {\n169\t\t\tif i != 0 {\n170\t\t\t\tbuf = append(buf, ',')\n171\t\t\t}\n172\t\t\tif x.IsNaN() {\n173\t\t\t\tbuf = append(buf, `null`...)\n174\t\t\t} else {\n175\t\t\t\tbuf = strconv.AppendFloat(buf, float64(x), 'f', 1, 32)\n176\t\t\t}\n177\t\t}\n178\t\tbuf = append(buf, `]}`...)\n179\t\treturn buf, nil\n180\t}\n181\t\n182\t// ToCheckpoint writes metric data to checkpoint files in parallel (JSON format).\n183\t//\n184\t// Metrics at root and cluster levels are skipped. One file per host is created.\n185\t// Uses worker pool (Keys.NumWorkers) for parallel processing. Only locks one host\n186\t// at a time, allowing concurrent writes/reads to other hosts.\n187\t//\n188\t// Returns the number of checkpoint files created and any errors encountered.\n189\tfunc (m *MemoryStore) ToCheckpoint(dir string, from, to int64) (int, error) {\n190\t\t// Pre-calculate capacity by counting cluster/host pairs\n191\t\tm.root.lock.RLock()\n192\t\ttotalHosts := 0\n193\t\tfor _, l1 := range m.root.children {\n194\t\t\tl1.lock.RLock()\n195\t\t\ttotalHosts += len(l1.children)\n196\t\t\tl1.lock.RUnlock()\n197\t\t}\n198\t\tm.root.lock.RUnlock()\n199\t\n200\t\tlevels := make([]*Level, 0, totalHosts)\n201\t\tselectors := make([][]string, 0, totalHosts)\n202\t\n203\t\tm.root.lock.RLock()\n204\t\tfor sel1, l1 := range m.root.children {\n205\t\t\tl1.lock.RLock()\n206\t\t\tfor sel2, l2 := range l1.children {\n207\t\t\t\tlevels = append(levels, l2)\n208\t\t\t\tselectors = append(selectors, []string{sel1, sel2})\n209\t\t\t}"}]},"uuid":"f321c935-a031-4137-b164-399b02e5a587","timestamp":"2026-03-29T09:07:41.292Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go","content":"\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n\t\t\t\t\t}\n\t\t\t\t\tif n > 0 {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n\t\t\t\t\t\tRotateWALFiles(hostDirs)\n\t\t\t\t\t}\n\t\t\t\t} else {\n\t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> checkpointing failed: %s\", err.Error())\n\t\t\t\t\t} else {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d checkpoint files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\t})\n}\n\n// MarshalJSON provides optimized JSON encoding for CheckpointMetrics.\n//\n// Since schema.Float has custom MarshalJSON, serializing []Float has significant overhead.\n// This method manually constructs JSON to avoid allocations and interface conversions.\nfunc (cm *CheckpointMetrics) MarshalJSON() ([]byte, error) {\n\tbuf := make([]byte, 0, 128+len(cm.Data)*8)\n\tbuf = append(buf, `{\"frequency\":`...)\n\tbuf = strconv.AppendInt(buf, cm.Frequency, 10)\n\tbuf = append(buf, `,\"start\":`...)\n\tbuf = strconv.AppendInt(buf, cm.Start, 10)\n\tbuf = append(buf, `,\"data\":[`...)\n\tfor i, x := range cm.Data {\n\t\tif i != 0 {\n\t\t\tbuf = append(buf, ',')\n\t\t}\n\t\tif x.IsNaN() {\n\t\t\tbuf = append(buf, `null`...)\n\t\t} else {\n\t\t\tbuf = strconv.AppendFloat(buf, float64(x), 'f', 1, 32)\n\t\t}\n\t}\n\tbuf = append(buf, `]}`...)\n\treturn buf, nil\n}\n\n// ToCheckpoint writes metric data to checkpoint files in parallel (JSON format).\n//\n// Metrics at root and cluster levels are skipped. One file per host is created.\n// Uses worker pool (Keys.NumWorkers) for parallel processing. Only locks one host\n// at a time, allowing concurrent writes/reads to other hosts.\n//\n// Returns the number of checkpoint files created and any errors encountered.\nfunc (m *MemoryStore) ToCheckpoint(dir string, from, to int64) (int, error) {\n\t// Pre-calculate capacity by counting cluster/host pairs\n\tm.root.lock.RLock()\n\ttotalHosts := 0\n\tfor _, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\ttotalHosts += len(l1.children)\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\tlevels := make([]*Level, 0, totalHosts)\n\tselectors := make([][]string, 0, totalHosts)\n\n\tm.root.lock.RLock()\n\tfor sel1, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\tfor sel2, l2 := range l1.children {\n\t\t\tlevels = append(levels, l2)\n\t\t\tselectors = append(selectors, []string{sel1, sel2})\n\t\t}","numLines":80,"startLine":130,"totalLines":671}},"sourceToolAssistantUUID":"45c03207-645e-4747-bf96-481fde8e7a33","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"f321c935-a031-4137-b164-399b02e5a587","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01QokbBLmE9DmTVVSAURqkBZ","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_011TmZWkKbNG6pmaLmCL2Qzf","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","limit":30,"offset":100},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3377,"cache_read_input_tokens":36548,"output_tokens":1605,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":3377,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX79kUVkQWBEDRF8LWeJ","type":"assistant","uuid":"fc768b83-2f16-4705-8c92-222e8c25928a","timestamp":"2026-03-29T09:07:41.928Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"fc768b83-2f16-4705-8c92-222e8c25928a","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_011TmZWkKbNG6pmaLmCL2Qzf","type":"tool_result","content":"100\tvar walShuttingDown atomic.Bool\n101\t\n102\t// WALMessage represents a single metric write to be appended to the WAL.\n103\t// Cluster and Node are NOT stored in the WAL record (inferred from file path).\n104\ttype WALMessage struct {\n105\t\tMetricName string\n106\t\tCluster string\n107\t\tNode string\n108\t\tSelector []string\n109\t\tValue schema.Float\n110\t\tTimestamp int64\n111\t}\n112\t\n113\t// walRotateReq requests WAL file rotation for a specific host directory.\n114\t// The done channel is closed by the WAL goroutine when rotation is complete.\n115\ttype walRotateReq struct {\n116\t\thostDir string\n117\t\tdone chan struct{}\n118\t}\n119\t\n120\t// walFileState holds an open WAL file handle and buffered writer for one host directory.\n121\ttype walFileState struct {\n122\t\tf *os.File\n123\t\tw *bufio.Writer\n124\t\tdirty bool\n125\t\tsize int64 // approximate bytes written (tracked from open + writes)\n126\t}\n127\t\n128\t// walFlushInterval controls how often dirty WAL files are flushed to disk.\n129\t// Decoupling flushes from message processing lets the consumer run at memory"}]},"uuid":"e3b0728a-e7b0-4948-8d80-cf0caf696fc8","timestamp":"2026-03-29T09:07:41.949Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"var walShuttingDown atomic.Bool\n\n// WALMessage represents a single metric write to be appended to the WAL.\n// Cluster and Node are NOT stored in the WAL record (inferred from file path).\ntype WALMessage struct {\n\tMetricName string\n\tCluster string\n\tNode string\n\tSelector []string\n\tValue schema.Float\n\tTimestamp int64\n}\n\n// walRotateReq requests WAL file rotation for a specific host directory.\n// The done channel is closed by the WAL goroutine when rotation is complete.\ntype walRotateReq struct {\n\thostDir string\n\tdone chan struct{}\n}\n\n// walFileState holds an open WAL file handle and buffered writer for one host directory.\ntype walFileState struct {\n\tf *os.File\n\tw *bufio.Writer\n\tdirty bool\n\tsize int64 // approximate bytes written (tracked from open + writes)\n}\n\n// walFlushInterval controls how often dirty WAL files are flushed to disk.\n// Decoupling flushes from message processing lets the consumer run at memory","numLines":30,"startLine":100,"totalLines":982}},"sourceToolAssistantUUID":"fc768b83-2f16-4705-8c92-222e8c25928a","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"e3b0728a-e7b0-4948-8d80-cf0caf696fc8","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01HbVe9pAEkp9Sd8pmNyGFNa","type":"message","role":"assistant","content":[{"type":"text","text":"Now let me also check if there's an existing pause mechanism and look at the config for numWorkers."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3003,"cache_read_input_tokens":39925,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":3003},"output_tokens":2,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7CDNKAQM9D5qxaPzMk","type":"assistant","uuid":"6c05f968-14ec-4c97-be1a-5a11eee1ee73","timestamp":"2026-03-29T09:07:46.618Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"6c05f968-14ec-4c97-be1a-5a11eee1ee73","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01HbVe9pAEkp9Sd8pmNyGFNa","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01B2C3sfdMf4Pba4GcjCEsZ1","name":"Grep","input":{"pattern":"walDropped|walPaused|checkpointing.*atomic|skipWAL","path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore","output_mode":"content"},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3003,"cache_read_input_tokens":39925,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":3003},"output_tokens":2,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7CDNKAQM9D5qxaPzMk","type":"assistant","uuid":"824b4f34-4f57-4b9f-bf80-f75009b9478d","timestamp":"2026-03-29T09:07:48.282Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"824b4f34-4f57-4b9f-bf80-f75009b9478d","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01B2C3sfdMf4Pba4GcjCEsZ1","type":"tool_result","content":"pkg/metricstore/lineprotocol.go:127:// walDropped counts WAL messages dropped due to a full channel.\npkg/metricstore/lineprotocol.go:129:var walDropped atomic.Int64\npkg/metricstore/lineprotocol.go:367:\t\t\t\tif dropped := walDropped.Add(1); dropped%10000 == 1 {"}]},"uuid":"11d37dee-1cb3-455f-9b8d-31ee38f40bf9","timestamp":"2026-03-29T09:07:48.305Z","toolUseResult":{"mode":"content","numFiles":0,"filenames":[],"content":"pkg/metricstore/lineprotocol.go:127:// walDropped counts WAL messages dropped due to a full channel.\npkg/metricstore/lineprotocol.go:129:var walDropped atomic.Int64\npkg/metricstore/lineprotocol.go:367:\t\t\t\tif dropped := walDropped.Add(1); dropped%10000 == 1 {","numLines":3},"sourceToolAssistantUUID":"824b4f34-4f57-4b9f-bf80-f75009b9478d","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"11d37dee-1cb3-455f-9b8d-31ee38f40bf9","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01HbVe9pAEkp9Sd8pmNyGFNa","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01BRq6V7uaqCMuRHdGfV1jge","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","limit":20,"offset":85},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":3003,"cache_read_input_tokens":39925,"output_tokens":249,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":3003,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7CDNKAQM9D5qxaPzMk","type":"assistant","uuid":"697e0458-d2c4-4b50-bcf6-44e0926a5b5a","timestamp":"2026-03-29T09:07:48.639Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"697e0458-d2c4-4b50-bcf6-44e0926a5b5a","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01BRq6V7uaqCMuRHdGfV1jge","type":"tool_result","content":"85\t// walShardChs holds per-shard channels for WAL messages.\n86\t// Initialized by WALStaging; nil when WAL is not active.\n87\tvar walShardChs []chan *WALMessage\n88\t\n89\t// walShardRotateChs holds per-shard channels for WAL rotation requests.\n90\tvar walShardRotateChs []chan walRotateReq\n91\t\n92\t// walNumShards stores the number of shards (set during WALStaging init).\n93\tvar walNumShards int\n94\t\n95\t// walStagingWg tracks WALStaging goroutine exits for shutdown synchronization.\n96\tvar walStagingWg sync.WaitGroup\n97\t\n98\t// walShuttingDown is set before closing shard channels to prevent\n99\t// SendWALMessage from sending on a closed channel (which panics in Go).\n100\tvar walShuttingDown atomic.Bool\n101\t\n102\t// WALMessage represents a single metric write to be appended to the WAL.\n103\t// Cluster and Node are NOT stored in the WAL record (inferred from file path).\n104\ttype WALMessage struct {"}]},"uuid":"1b72fbe7-ea12-4ee0-a1a3-2586bdb7869c","timestamp":"2026-03-29T09:07:48.648Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"// walShardChs holds per-shard channels for WAL messages.\n// Initialized by WALStaging; nil when WAL is not active.\nvar walShardChs []chan *WALMessage\n\n// walShardRotateChs holds per-shard channels for WAL rotation requests.\nvar walShardRotateChs []chan walRotateReq\n\n// walNumShards stores the number of shards (set during WALStaging init).\nvar walNumShards int\n\n// walStagingWg tracks WALStaging goroutine exits for shutdown synchronization.\nvar walStagingWg sync.WaitGroup\n\n// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool\n\n// WALMessage represents a single metric write to be appended to the WAL.\n// Cluster and Node are NOT stored in the WAL record (inferred from file path).\ntype WALMessage struct {","numLines":20,"startLine":85,"totalLines":982}},"sourceToolAssistantUUID":"697e0458-d2c4-4b50-bcf6-44e0926a5b5a","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"1b72fbe7-ea12-4ee0-a1a3-2586bdb7869c","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_0135TFwxtYsmpCJuVywqt37f","type":"message","role":"assistant","content":[{"type":"text","text":"Now let me also look at the RotateWALFiles function and check if the WAL deletion in ToCheckpointWAL (line 731) races with the staging goroutine."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":687,"cache_read_input_tokens":42928,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":687},"output_tokens":1,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7Chw2ras51kfcZuMNp","type":"assistant","uuid":"d731db06-7fc2-4d9a-8e70-3ca3f30ed351","timestamp":"2026-03-29T09:07:52.905Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"d731db06-7fc2-4d9a-8e70-3ca3f30ed351","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_0135TFwxtYsmpCJuVywqt37f","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_011tNgin4cHqvgPQxGWgkXnY","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","limit":60,"offset":350},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":687,"cache_read_input_tokens":42928,"output_tokens":159,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":687,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7Chw2ras51kfcZuMNp","type":"assistant","uuid":"140efddc-0229-49d8-962c-c8805f14e9e7","timestamp":"2026-03-29T09:07:53.566Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"140efddc-0229-49d8-962c-c8805f14e9e7","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_011tNgin4cHqvgPQxGWgkXnY","type":"tool_result","content":"350\t\n351\t// RotateWALFiles sends rotation requests for the given host directories\n352\t// and blocks until all rotations complete. Each request is routed to the\n353\t// shard that owns the host directory.\n354\t//\n355\t// If shutdown is in progress (WAL staging goroutines may have exited),\n356\t// rotation is skipped to avoid deadlocking on abandoned channels.\n357\tfunc RotateWALFiles(hostDirs []string) {\n358\t\tif walShardRotateChs == nil || walShuttingDown.Load() {\n359\t\t\treturn\n360\t\t}\n361\t\tdeadline := time.After(2 * time.Minute)\n362\t\tdones := make([]chan struct{}, 0, len(hostDirs))\n363\t\tfor _, dir := range hostDirs {\n364\t\t\tdone := make(chan struct{})\n365\t\t\tshard := walShardIndexFromDir(dir)\n366\t\t\tselect {\n367\t\t\tcase walShardRotateChs[shard] <- walRotateReq{hostDir: dir, done: done}:\n368\t\t\t\tdones = append(dones, done)\n369\t\t\tcase <-deadline:\n370\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL rotation send timed out, %d of %d hosts remaining\",\n371\t\t\t\t\tlen(hostDirs)-len(dones), len(hostDirs))\n372\t\t\t\tgoto waitDones\n373\t\t\t}\n374\t\t}\n375\twaitDones:\n376\t\tfor _, done := range dones {\n377\t\t\tselect {\n378\t\t\tcase <-done:\n379\t\t\tcase <-time.After(30 * time.Second):\n380\t\t\t\tcclog.Warn(\"[METRICSTORE]> WAL rotation completion timed out, continuing\")\n381\t\t\t\treturn\n382\t\t\t}\n383\t\t}\n384\t}\n385\t\n386\t// walShardIndexFromDir extracts cluster and node from a host directory path\n387\t// and returns the shard index. The path format is: rootDir/cluster/node\n388\tfunc walShardIndexFromDir(hostDir string) int {\n389\t\t// hostDir = .../cluster/node — extract last two path components\n390\t\tnode := path.Base(hostDir)\n391\t\tcluster := path.Base(path.Dir(hostDir))\n392\t\treturn walShardIndex(cluster, node)\n393\t}\n394\t\n395\t// RotateWALFiles sends rotation requests for the given host directories\n396\t// and blocks until all rotations complete.\n397\tfunc RotateWALFilesAfterShutdown(hostDirs []string) {\n398\t\tfor _, dir := range hostDirs {\n399\t\t\twalPath := path.Join(dir, \"current.wal\")\n400\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n401\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n402\t\t\t}\n403\t\t}\n404\t}\n405\t\n406\t// writeWALRecordDirect encodes a WAL record into a contiguous buffer first,\n407\t// then writes it to the bufio.Writer in a single call. This prevents partial\n408\t// records in the write buffer if a write error occurs mid-record (e.g. disk full).\n409\t// Returns the number of bytes written and any error."}]},"uuid":"ba365d12-facd-4a07-8583-ef42a3d53f02","timestamp":"2026-03-29T09:07:53.574Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","content":"\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete. Each request is routed to the\n// shard that owns the host directory.\n//\n// If shutdown is in progress (WAL staging goroutines may have exited),\n// rotation is skipped to avoid deadlocking on abandoned channels.\nfunc RotateWALFiles(hostDirs []string) {\n\tif walShardRotateChs == nil || walShuttingDown.Load() {\n\t\treturn\n\t}\n\tdeadline := time.After(2 * time.Minute)\n\tdones := make([]chan struct{}, 0, len(hostDirs))\n\tfor _, dir := range hostDirs {\n\t\tdone := make(chan struct{})\n\t\tshard := walShardIndexFromDir(dir)\n\t\tselect {\n\t\tcase walShardRotateChs[shard] <- walRotateReq{hostDir: dir, done: done}:\n\t\t\tdones = append(dones, done)\n\t\tcase <-deadline:\n\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL rotation send timed out, %d of %d hosts remaining\",\n\t\t\t\tlen(hostDirs)-len(dones), len(hostDirs))\n\t\t\tgoto waitDones\n\t\t}\n\t}\nwaitDones:\n\tfor _, done := range dones {\n\t\tselect {\n\t\tcase <-done:\n\t\tcase <-time.After(30 * time.Second):\n\t\t\tcclog.Warn(\"[METRICSTORE]> WAL rotation completion timed out, continuing\")\n\t\t\treturn\n\t\t}\n\t}\n}\n\n// walShardIndexFromDir extracts cluster and node from a host directory path\n// and returns the shard index. The path format is: rootDir/cluster/node\nfunc walShardIndexFromDir(hostDir string) int {\n\t// hostDir = .../cluster/node — extract last two path components\n\tnode := path.Base(hostDir)\n\tcluster := path.Base(path.Dir(hostDir))\n\treturn walShardIndex(cluster, node)\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFilesAfterShutdown(hostDirs []string) {\n\tfor _, dir := range hostDirs {\n\t\twalPath := path.Join(dir, \"current.wal\")\n\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t}\n\t}\n}\n\n// writeWALRecordDirect encodes a WAL record into a contiguous buffer first,\n// then writes it to the bufio.Writer in a single call. This prevents partial\n// records in the write buffer if a write error occurs mid-record (e.g. disk full).\n// Returns the number of bytes written and any error.","numLines":60,"startLine":350,"totalLines":982}},"sourceToolAssistantUUID":"140efddc-0229-49d8-962c-c8805f14e9e7","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} 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{"parentUuid":"5bed4624-45ec-4d81-85d7-484b8393b7bb","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01EEDr7Vvsc2XJuAawzZTAJi","type":"message","role":"assistant","content":[{"type":"text","text":"Now I have a thorough understanding of the problem. Let me design the plan."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":979,"cache_read_input_tokens":43615,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":979},"output_tokens":44,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7D4x5HZnPZ8NtyodKx","type":"assistant","uuid":"f5654deb-6c80-4185-a3b1-b1e8f14bd0ae","timestamp":"2026-03-29T09:08:26.017Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"f5654deb-6c80-4185-a3b1-b1e8f14bd0ae","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01EEDr7Vvsc2XJuAawzZTAJi","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01CgQysKimqt4cMmYNo7QnEC","name":"Agent","input":{"subagent_type":"Plan","description":"Design WAL checkpoint fix","prompt":"Design an implementation to fix WAL shard channel saturation during binary checkpointing in a metric store.\n\n## Problem\nDuring periodic binary checkpoints (every 12h), ~1.44M WAL messages are dropped because shard channels fill up. The checkpoint takes 1845 hosts × 10 workers and runs for ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint writes.\n\n## Key Insight\nWAL writes during checkpoint are REDUNDANT: the binary snapshot captures ALL in-memory data. After checkpoint, WAL files are rotated (deleted). So any WAL writes during the checkpoint window are wasted work that will be immediately discarded.\n\n## Current Architecture\n- `lineprotocol.go:364`: `SendWALMessage(msg)` — non-blocking send to shard channel, drops if full\n- `walCheckpoint.go:100`: `var walShuttingDown atomic.Bool` — existing flag for shutdown\n- `walCheckpoint.go:145-156`: `SendWALMessage()` — checks `walShuttingDown`, then does select send\n- `walCheckpoint.go:658`: `ToCheckpointWAL()` — the binary checkpoint writer\n- `checkpoint.go:128-139`: Checkpointing goroutine calls `ToCheckpointWAL()` then `RotateWALFiles()`\n- `walCheckpoint.go:730-733`: Inside ToCheckpointWAL, each worker deletes WAL immediately after successful snapshot (race with staging goroutine that still has file open!)\n\n## Proposed Fix: Pause WAL during checkpoint\n\nAdd an atomic flag `walCheckpointActive` that causes `SendWALMessage` to skip sending (return true, not false — because data is safe in memory and snapshot will capture it). Set the flag before checkpoint starts, clear it after checkpoint + rotation completes.\n\n### Specific changes:\n\n1. **walCheckpoint.go**: Add `var walCheckpointActive atomic.Bool` next to `walShuttingDown`\n\n2. **walCheckpoint.go:SendWALMessage()**: Add early return if `walCheckpointActive.Load()` — return `true` (not false) since data isn't lost\n\n3. **checkpoint.go**: Set `walCheckpointActive.Store(true)` before calling `ToCheckpointWAL()`, and `walCheckpointActive.Store(false)` after `RotateWALFiles()` completes. Also reset `walDropped` counter.\n\n4. **Also fix the race condition**: ToCheckpointWAL line 730-733 deletes WAL directly from checkpoint worker while staging goroutine has the file open. This should be removed — RotateWALFiles already handles this properly via the staging goroutine.\n\n### Benefits:\n- Zero WAL drops during checkpoint (nothing to drop)\n- Reduced disk I/O during checkpoint (no WAL writes competing)\n- Faster checkpoint completion\n- Eliminates the file deletion race condition\n\n### Concerns to address:\n- If the process crashes DURING checkpoint (after snapshot written for some hosts but not all), the pre-checkpoint WAL data for un-snapshotted hosts is needed for recovery. But since we're pausing WAL writes for NEW incoming data (which is already in memory), and the existing WAL files are untouched until after snapshot succeeds, crash recovery is fine.\n\nPlease evaluate this approach and suggest any improvements or issues."},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":979,"cache_read_input_tokens":43615,"output_tokens":2191,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":979,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7D4x5HZnPZ8NtyodKx","type":"assistant","uuid":"72d8e871-b04b-4340-892b-2ab791f52b11","timestamp":"2026-03-29T09:08:43.534Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"72d8e871-b04b-4340-892b-2ab791f52b11","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01CgQysKimqt4cMmYNo7QnEC","type":"tool_result","content":[{"type":"text","text":"Now I have a complete picture. Let me provide the evaluation.\n\n---\n\n## Evaluation of the Proposed Approach\n\nThe proposal is fundamentally sound. I have verified the code paths and confirmed the key claims. Here is a detailed analysis.\n\n### Confirming the Architecture\n\nThe flow is:\n\n1. `DecodeLine()` in `lineprotocol.go` writes each metric to both the in-memory store (`WriteToLevel`) and the WAL (`SendWALMessage`) at line 355-369.\n2. `SendWALMessage()` in `walCheckpoint.go:145-156` does a non-blocking send to a shard channel. If the channel is full, it returns `false` and the caller increments `walDropped`.\n3. `Checkpointing()` in `checkpoint.go:128-139` calls `ToCheckpointWAL()` then `RotateWALFiles()`.\n4. `ToCheckpointWAL()` in `walCheckpoint.go:658-760` writes binary snapshots for all hosts in parallel, and **on line 730-733, each worker deletes the WAL file directly via `os.Remove`**.\n5. `RotateWALFiles()` in `walCheckpoint.go:357-384` sends rotation requests through the shard channels to the staging goroutines, which close the file handle, delete the file, and remove it from their map.\n\n### Confirmed Issues\n\n**Issue 1: WAL writes during checkpoint are wasted work.** Correct. The binary snapshot at `toCheckpointBinary` reads directly from the in-memory Level tree (via `toCheckpointFile`), capturing everything currently in memory. After the snapshot, `RotateWALFiles` deletes the WAL. Any WAL records written during this window are immediately discarded.\n\n**Issue 2: Race condition on WAL file deletion (lines 730-733).** This is a real bug. The checkpoint worker calls `os.Remove(walPath)` directly on the WAL file while the staging goroutine in `WALStaging` may still have the file open via its `walFileState` map entry. The staging goroutine's `getOrOpenWAL` caches file handles in `hostFiles`, and nothing tells it the file was deleted. On Linux, the staging goroutine can continue writing to the unlinked fd (data goes nowhere), and when it next opens a new WAL, it creates a fresh file. But on some edge cases, this can cause confusing behavior. More importantly, `RotateWALFiles` is called right after (checkpoint.go:139), which sends a rotation request through the proper channel -- but by then the file is already deleted by the worker, so the staging goroutine tries to remove an already-gone file (benign due to the `!os.IsNotExist` guard) and closes the handle.\n\nThe double-delete is wasteful but not catastrophic. However, the staging goroutine still holds a stale `walFileState` entry between the worker's `os.Remove` and the rotation request arriving. During that window, any incoming WAL messages for that host would be written to the deleted fd (on Linux) or fail (on other platforms).\n\n### Evaluation of the Proposed Fix\n\nThe proposal to add `walCheckpointActive atomic.Bool` is clean and correct. Here is my assessment of each change:\n\n**Change 1: Add `var walCheckpointActive atomic.Bool`** -- Straightforward. Place it next to `walShuttingDown` at line 100 for clarity.\n\n**Change 2: Early return in `SendWALMessage` returning `true`** -- Correct. Returning `true` is the right choice because the data is not lost; it is in-memory and will be captured by the snapshot. This also prevents the `walDropped` counter from being incremented in `lineprotocol.go:367`, which is the desired behavior (no false alarms).\n\n**Change 3: Set/clear flag around checkpoint + rotation in `checkpoint.go`** -- Correct. The flag should be set before `ToCheckpointWAL()` and cleared after `RotateWALFiles()` completes, so the entire window of snapshot-write + WAL-rotation is covered.\n\n**Change 4: Remove direct WAL deletion in ToCheckpointWAL lines 730-733** -- This is the most important fix. The `os.Remove` on line 731-733 should be removed entirely. `RotateWALFiles` (called from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate` function (walCheckpoint.go:271-283), which flushes, closes the handle, removes the file, and cleans up the map entry. The direct delete is both redundant and racy.\n\n### Suggested Improvements\n\n**1. Reset `walDropped` counter after checkpoint.** The proposal mentions this. After clearing the flag, add `walDropped.Store(0)` in `checkpoint.go` so the next checkpoint cycle starts with a clean count. This avoids confusing log messages that show accumulated drops from previous cycles.\n\n**2. Log the pause/resume.** Add a brief info log when the flag is set and cleared, so operators can correlate any timing anomalies:\n```\ncclog.Infof(\"[METRICSTORE]> pausing WAL writes during binary checkpoint\")\n// ... checkpoint + rotate ...\ncclog.Infof(\"[METRICSTORE]> resuming WAL writes after binary checkpoint\")\n```\n\n**3. Consider a defer for clearing the flag.** If `ToCheckpointWAL` returns an error, the current proposal in `checkpoint.go:128-139` does not call `RotateWALFiles` (it only rotates when `n > 0`). The flag would remain set forever, permanently disabling WAL writes. Use a `defer` or ensure the flag is cleared in all exit paths:\n\nLooking at `checkpoint.go:128-139`:\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ...\n RotateWALFiles(hostDirs)\n }\n}\n```\n\nIf `ToCheckpointWAL` returns `n=0` with an error, the flag would never be cleared. The flag must be cleared unconditionally. The safest pattern:\n\n```go\nwalCheckpointActive.Store(true)\ndefer walCheckpointActive.Store(false)\n```\n\nThis should be placed just before the `ToCheckpointWAL` call, within the `if Keys.Checkpoints.FileFormat == \"wal\"` block.\n\n**4. Drain shard channels after clearing the flag (optional optimization).** When the flag is cleared, the shard channels are empty (no messages were queued during the pause). This is actually beneficial -- the staging goroutines have an empty pipeline and can immediately start processing new messages without backlog. No drain step needed.\n\n**5. Crash safety analysis.** The proposal's crash safety argument is correct. During the checkpoint window:\n- Pre-existing WAL files on disk remain untouched until `RotateWALFiles` (which happens after all snapshots succeed).\n- New incoming metrics are written to the in-memory store (line 373 in `lineprotocol.go` runs regardless of WAL status).\n- If the process crashes mid-checkpoint, on restart `fromCheckpoint` loads the most recent complete `.bin` snapshot plus replays the pre-existing `current.wal`. No data is lost because: (a) snapshots use atomic rename (`.bin.tmp` -> `.bin`), so partial snapshots are invisible; (b) the old WAL is still on disk.\n- The only risk: metrics that arrive DURING checkpoint but AFTER the snapshot reads a particular host's in-memory data would not be in either the snapshot or the WAL. This is a very small window (the read lock in `toCheckpointFile` is brief) and would affect at most a few seconds of data. This is the same risk that exists today (those metrics would have been written to WAL, but the WAL would have been deleted post-checkpoint anyway). So the proposal does not make crash safety any worse.\n\n### Implementation Plan\n\n**Step 1**: In `walCheckpoint.go`, add `var walCheckpointActive atomic.Bool` at line ~100, next to `walShuttingDown`.\n\n**Step 2**: In `walCheckpoint.go`, modify `SendWALMessage()` (lines 145-156) to check the new flag:\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n shard := walShardIndex(msg.Cluster, msg.Node)\n select {\n case walShardChs[shard] <- msg:\n return true\n default:\n return false\n }\n}\n```\n\n**Step 3**: In `walCheckpoint.go`, remove lines 730-733 (the direct `os.Remove` of WAL files inside `ToCheckpointWAL` workers). Keep the `successDirs` tracking since `RotateWALFiles` still needs it.\n\n**Step 4**: In `checkpoint.go`, wrap the WAL checkpoint block (lines 128-139) with the flag:\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n cclog.Infof(...)\n lastCheckpointMu.Lock()\n lastCheckpoint = now\n lastCheckpointMu.Unlock()\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false)\n walDropped.Store(0)\n}\n```\n\nNote that `walCheckpointActive.Store(false)` is placed outside the `if n > 0` block to ensure it is always cleared, even on full failure.\n\n**Step 5**: Add tests. A unit test should verify that `SendWALMessage` returns `true` (not `false`) when `walCheckpointActive` is set, confirming the caller won't increment `walDropped`.\n\n### Critical Files for Implementation\n- /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go\n- /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go\n- /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/lineprotocol.go"}]}]},"uuid":"fabcd0b1-8367-43da-9abe-997ef379e804","timestamp":"2026-03-29T09:10:12.535Z","toolUseResult":{"status":"completed","prompt":"Design an implementation to fix WAL shard channel saturation during binary checkpointing in a metric store.\n\n## Problem\nDuring periodic binary checkpoints (every 12h), ~1.44M WAL messages are dropped because shard channels fill up. The checkpoint takes 1845 hosts × 10 workers and runs for ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint writes.\n\n## Key Insight\nWAL writes during checkpoint are REDUNDANT: the binary snapshot captures ALL in-memory data. After checkpoint, WAL files are rotated (deleted). So any WAL writes during the checkpoint window are wasted work that will be immediately discarded.\n\n## Current Architecture\n- `lineprotocol.go:364`: `SendWALMessage(msg)` — non-blocking send to shard channel, drops if full\n- `walCheckpoint.go:100`: `var walShuttingDown atomic.Bool` — existing flag for shutdown\n- `walCheckpoint.go:145-156`: `SendWALMessage()` — checks `walShuttingDown`, then does select send\n- `walCheckpoint.go:658`: `ToCheckpointWAL()` — the binary checkpoint writer\n- `checkpoint.go:128-139`: Checkpointing goroutine calls `ToCheckpointWAL()` then `RotateWALFiles()`\n- `walCheckpoint.go:730-733`: Inside ToCheckpointWAL, each worker deletes WAL immediately after successful snapshot (race with staging goroutine that still has file open!)\n\n## Proposed Fix: Pause WAL during checkpoint\n\nAdd an atomic flag `walCheckpointActive` that causes `SendWALMessage` to skip sending (return true, not false — because data is safe in memory and snapshot will capture it). Set the flag before checkpoint starts, clear it after checkpoint + rotation completes.\n\n### Specific changes:\n\n1. **walCheckpoint.go**: Add `var walCheckpointActive atomic.Bool` next to `walShuttingDown`\n\n2. **walCheckpoint.go:SendWALMessage()**: Add early return if `walCheckpointActive.Load()` — return `true` (not false) since data isn't lost\n\n3. **checkpoint.go**: Set `walCheckpointActive.Store(true)` before calling `ToCheckpointWAL()`, and `walCheckpointActive.Store(false)` after `RotateWALFiles()` completes. Also reset `walDropped` counter.\n\n4. **Also fix the race condition**: ToCheckpointWAL line 730-733 deletes WAL directly from checkpoint worker while staging goroutine has the file open. This should be removed — RotateWALFiles already handles this properly via the staging goroutine.\n\n### Benefits:\n- Zero WAL drops during checkpoint (nothing to drop)\n- Reduced disk I/O during checkpoint (no WAL writes competing)\n- Faster checkpoint completion\n- Eliminates the file deletion race condition\n\n### Concerns to address:\n- If the process crashes DURING checkpoint (after snapshot written for some hosts but not all), the pre-checkpoint WAL data for un-snapshotted hosts is needed for recovery. But since we're pausing WAL writes for NEW incoming data (which is already in memory), and the existing WAL files are untouched until after snapshot succeeds, crash recovery is fine.\n\nPlease evaluate this approach and suggest any improvements or issues.","agentId":"a7963bf1130e8b9e7","agentType":"Plan","content":[{"type":"text","text":"Now I have a complete picture. Let me provide the evaluation.\n\n---\n\n## Evaluation of the Proposed Approach\n\nThe proposal is fundamentally sound. I have verified the code paths and confirmed the key claims. Here is a detailed analysis.\n\n### Confirming the Architecture\n\nThe flow is:\n\n1. `DecodeLine()` in `lineprotocol.go` writes each metric to both the in-memory store (`WriteToLevel`) and the WAL (`SendWALMessage`) at line 355-369.\n2. `SendWALMessage()` in `walCheckpoint.go:145-156` does a non-blocking send to a shard channel. If the channel is full, it returns `false` and the caller increments `walDropped`.\n3. `Checkpointing()` in `checkpoint.go:128-139` calls `ToCheckpointWAL()` then `RotateWALFiles()`.\n4. `ToCheckpointWAL()` in `walCheckpoint.go:658-760` writes binary snapshots for all hosts in parallel, and **on line 730-733, each worker deletes the WAL file directly via `os.Remove`**.\n5. `RotateWALFiles()` in `walCheckpoint.go:357-384` sends rotation requests through the shard channels to the staging goroutines, which close the file handle, delete the file, and remove it from their map.\n\n### Confirmed Issues\n\n**Issue 1: WAL writes during checkpoint are wasted work.** Correct. The binary snapshot at `toCheckpointBinary` reads directly from the in-memory Level tree (via `toCheckpointFile`), capturing everything currently in memory. After the snapshot, `RotateWALFiles` deletes the WAL. Any WAL records written during this window are immediately discarded.\n\n**Issue 2: Race condition on WAL file deletion (lines 730-733).** This is a real bug. The checkpoint worker calls `os.Remove(walPath)` directly on the WAL file while the staging goroutine in `WALStaging` may still have the file open via its `walFileState` map entry. The staging goroutine's `getOrOpenWAL` caches file handles in `hostFiles`, and nothing tells it the file was deleted. On Linux, the staging goroutine can continue writing to the unlinked fd (data goes nowhere), and when it next opens a new WAL, it creates a fresh file. But on some edge cases, this can cause confusing behavior. More importantly, `RotateWALFiles` is called right after (checkpoint.go:139), which sends a rotation request through the proper channel -- but by then the file is already deleted by the worker, so the staging goroutine tries to remove an already-gone file (benign due to the `!os.IsNotExist` guard) and closes the handle.\n\nThe double-delete is wasteful but not catastrophic. However, the staging goroutine still holds a stale `walFileState` entry between the worker's `os.Remove` and the rotation request arriving. During that window, any incoming WAL messages for that host would be written to the deleted fd (on Linux) or fail (on other platforms).\n\n### Evaluation of the Proposed Fix\n\nThe proposal to add `walCheckpointActive atomic.Bool` is clean and correct. Here is my assessment of each change:\n\n**Change 1: Add `var walCheckpointActive atomic.Bool`** -- Straightforward. Place it next to `walShuttingDown` at line 100 for clarity.\n\n**Change 2: Early return in `SendWALMessage` returning `true`** -- Correct. Returning `true` is the right choice because the data is not lost; it is in-memory and will be captured by the snapshot. This also prevents the `walDropped` counter from being incremented in `lineprotocol.go:367`, which is the desired behavior (no false alarms).\n\n**Change 3: Set/clear flag around checkpoint + rotation in `checkpoint.go`** -- Correct. The flag should be set before `ToCheckpointWAL()` and cleared after `RotateWALFiles()` completes, so the entire window of snapshot-write + WAL-rotation is covered.\n\n**Change 4: Remove direct WAL deletion in ToCheckpointWAL lines 730-733** -- This is the most important fix. The `os.Remove` on line 731-733 should be removed entirely. `RotateWALFiles` (called from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate` function (walCheckpoint.go:271-283), which flushes, closes the handle, removes the file, and cleans up the map entry. The direct delete is both redundant and racy.\n\n### Suggested Improvements\n\n**1. Reset `walDropped` counter after checkpoint.** The proposal mentions this. After clearing the flag, add `walDropped.Store(0)` in `checkpoint.go` so the next checkpoint cycle starts with a clean count. This avoids confusing log messages that show accumulated drops from previous cycles.\n\n**2. Log the pause/resume.** Add a brief info log when the flag is set and cleared, so operators can correlate any timing anomalies:\n```\ncclog.Infof(\"[METRICSTORE]> pausing WAL writes during binary checkpoint\")\n// ... checkpoint + rotate ...\ncclog.Infof(\"[METRICSTORE]> resuming WAL writes after binary checkpoint\")\n```\n\n**3. Consider a defer for clearing the flag.** If `ToCheckpointWAL` returns an error, the current proposal in `checkpoint.go:128-139` does not call `RotateWALFiles` (it only rotates when `n > 0`). The flag would remain set forever, permanently disabling WAL writes. Use a `defer` or ensure the flag is cleared in all exit paths:\n\nLooking at `checkpoint.go:128-139`:\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ...\n RotateWALFiles(hostDirs)\n }\n}\n```\n\nIf `ToCheckpointWAL` returns `n=0` with an error, the flag would never be cleared. The flag must be cleared unconditionally. The safest pattern:\n\n```go\nwalCheckpointActive.Store(true)\ndefer walCheckpointActive.Store(false)\n```\n\nThis should be placed just before the `ToCheckpointWAL` call, within the `if Keys.Checkpoints.FileFormat == \"wal\"` block.\n\n**4. Drain shard channels after clearing the flag (optional optimization).** When the flag is cleared, the shard channels are empty (no messages were queued during the pause). This is actually beneficial -- the staging goroutines have an empty pipeline and can immediately start processing new messages without backlog. No drain step needed.\n\n**5. Crash safety analysis.** The proposal's crash safety argument is correct. During the checkpoint window:\n- Pre-existing WAL files on disk remain untouched until `RotateWALFiles` (which happens after all snapshots succeed).\n- New incoming metrics are written to the in-memory store (line 373 in `lineprotocol.go` runs regardless of WAL status).\n- If the process crashes mid-checkpoint, on restart `fromCheckpoint` loads the most recent complete `.bin` snapshot plus replays the pre-existing `current.wal`. No data is lost because: (a) snapshots use atomic rename (`.bin.tmp` -> `.bin`), so partial snapshots are invisible; (b) the old WAL is still on disk.\n- The only risk: metrics that arrive DURING checkpoint but AFTER the snapshot reads a particular host's in-memory data would not be in either the snapshot or the WAL. This is a very small window (the read lock in `toCheckpointFile` is brief) and would affect at most a few seconds of data. This is the same risk that exists today (those metrics would have been written to WAL, but the WAL would have been deleted post-checkpoint anyway). So the proposal does not make crash safety any worse.\n\n### Implementation Plan\n\n**Step 1**: In `walCheckpoint.go`, add `var walCheckpointActive atomic.Bool` at line ~100, next to `walShuttingDown`.\n\n**Step 2**: In `walCheckpoint.go`, modify `SendWALMessage()` (lines 145-156) to check the new flag:\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n shard := walShardIndex(msg.Cluster, msg.Node)\n select {\n case walShardChs[shard] <- msg:\n return true\n default:\n return false\n }\n}\n```\n\n**Step 3**: In `walCheckpoint.go`, remove lines 730-733 (the direct `os.Remove` of WAL files inside `ToCheckpointWAL` workers). Keep the `successDirs` tracking since `RotateWALFiles` still needs it.\n\n**Step 4**: In `checkpoint.go`, wrap the WAL checkpoint block (lines 128-139) with the flag:\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n cclog.Infof(...)\n lastCheckpointMu.Lock()\n lastCheckpoint = now\n lastCheckpointMu.Unlock()\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false)\n walDropped.Store(0)\n}\n```\n\nNote that `walCheckpointActive.Store(false)` is placed outside the `if n > 0` block to ensure it is always cleared, even on full failure.\n\n**Step 5**: Add tests. A unit test should verify that `SendWALMessage` returns `true` (not `false`) when `walCheckpointActive` is set, confirming the caller won't increment `walDropped`.\n\n### Critical Files for Implementation\n- /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go\n- /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go\n- /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/lineprotocol.go"}],"totalDurationMs":88724,"totalTokens":34315,"totalToolUseCount":10,"usage":{"input_tokens":1,"cache_creation_input_tokens":255,"cache_read_input_tokens":31448,"output_tokens":2611,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":0,"ephemeral_5m_input_tokens":255},"inference_geo":"","iterations":[],"speed":"standard"}},"sourceToolAssistantUUID":"72d8e871-b04b-4340-892b-2ab791f52b11","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"fabcd0b1-8367-43da-9abe-997ef379e804","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_016wFmaRykcCXxeebDdw7gpb","type":"message","role":"assistant","content":[{"type":"text","text":"\n\nGood analysis. Let me write the final plan."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":4924,"cache_read_input_tokens":44594,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":4924},"output_tokens":2,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7PLMorBu36UydTo1Ym","type":"assistant","uuid":"72bc7cca-fb86-4218-934c-b84b654bcb83","timestamp":"2026-03-29T09:10:16.644Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"72bc7cca-fb86-4218-934c-b84b654bcb83","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_016wFmaRykcCXxeebDdw7gpb","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01WgWsTJnRRJBEfbtzPRr3BD","name":"Write","input":{"file_path":"/Users/jan/.claude/plans/lovely-soaring-snail.md","content":"# Fix: WAL shard channel saturation during binary checkpoint\n\n## Context\n\nDuring periodic binary checkpoints (~every 12h), 1.44M+ WAL messages are dropped because shard channels fill up. The checkpoint processes 1845 hosts with 10 workers, taking ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint binary writes.\n\n**Key insight:** WAL writes during checkpoint are completely redundant — the binary snapshot reads directly from the in-memory Level tree, capturing everything. After the snapshot, WAL files are rotated (deleted). Any WAL records written during this window are immediately discarded.\n\n## Changes\n\n### 1. Add `walCheckpointActive` atomic flag (`walCheckpoint.go`)\n\nAdd `var walCheckpointActive atomic.Bool` at ~line 100, next to `walShuttingDown`.\n\n### 2. Skip WAL sends during checkpoint (`walCheckpoint.go:SendWALMessage`)\n\nAdd early return `true` (not `false` — data is safe in memory) when `walCheckpointActive.Load()` is set. This prevents channel pressure AND avoids incrementing `walDropped`.\n\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n // ... existing select/send logic\n}\n```\n\n### 3. Remove direct WAL deletion race in `ToCheckpointWAL` (`walCheckpoint.go:730-733`)\n\nRemove the `os.Remove(walPath)` inside the checkpoint worker loop. This races with the WAL staging goroutine that still has the file open. `RotateWALFiles` (called afterward from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate`.\n\n### 4. Set/clear flag around checkpoint (`checkpoint.go:~128-139`)\n\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ... existing success handling ...\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false) // Always clear, even on error\n walDropped.Store(0) // Reset drop counter\n}\n```\n\n## Files to modify\n\n- `pkg/metricstore/walCheckpoint.go` — add flag, modify `SendWALMessage`, remove direct WAL delete\n- `pkg/metricstore/checkpoint.go` — set/clear flag around checkpoint call\n- `pkg/metricstore/lineprotocol.go` — no changes needed (`walDropped` is already exported)\n\n## Crash safety\n\nNo regression. During the checkpoint window:\n- Pre-existing WAL files remain on disk until `RotateWALFiles` (after all snapshots succeed)\n- New metrics are still written to in-memory store (`WriteToLevel` at line 373 runs regardless)\n- If crash mid-checkpoint: restart loads latest complete `.bin` + replays old `current.wal` — no data loss since snapshots use atomic rename (`.bin.tmp` → `.bin`)\n\n## Verification\n\n1. `go build ./...` — compiles\n2. `go test ./pkg/metricstore/...` — existing tests pass\n3. Deploy and confirm no more \"WAL shard channel full, dropped N messages\" warnings during checkpoint\n4. Confirm checkpoint logs show normal \"Starting binary checkpoint\" → \"done: N binary snapshot files created\" without drops\n"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":4924,"cache_read_input_tokens":44594,"output_tokens":1018,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":4924,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7PLMorBu36UydTo1Ym","type":"assistant","uuid":"606423c2-3cb9-4899-868b-9fc576c35528","timestamp":"2026-03-29T09:10:30.825Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"type":"file-history-snapshot","messageId":"606423c2-3cb9-4899-868b-9fc576c35528","snapshot":{"messageId":"7fe64e31-f76e-403e-88ab-3a6e6ef368e7","trackedFileBackups":{"/Users/jan/.claude/plans/lovely-soaring-snail.md":{"backupFileName":null,"version":1,"backupTime":"2026-03-29T09:10:30.845Z"}},"timestamp":"2026-03-29T09:04:51.569Z"},"isSnapshotUpdate":true} {"parentUuid":"606423c2-3cb9-4899-868b-9fc576c35528","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01WgWsTJnRRJBEfbtzPRr3BD","type":"tool_result","content":"File created successfully at: /Users/jan/.claude/plans/lovely-soaring-snail.md"}]},"uuid":"f29d974f-6bd0-44d4-8ba2-c87b5d355b6a","timestamp":"2026-03-29T09:10:30.848Z","toolUseResult":{"type":"create","filePath":"/Users/jan/.claude/plans/lovely-soaring-snail.md","content":"# Fix: WAL shard channel saturation during binary checkpoint\n\n## Context\n\nDuring periodic binary checkpoints (~every 12h), 1.44M+ WAL messages are dropped because shard channels fill up. The checkpoint processes 1845 hosts with 10 workers, taking ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint binary writes.\n\n**Key insight:** WAL writes during checkpoint are completely redundant — the binary snapshot reads directly from the in-memory Level tree, capturing everything. After the snapshot, WAL files are rotated (deleted). Any WAL records written during this window are immediately discarded.\n\n## Changes\n\n### 1. Add `walCheckpointActive` atomic flag (`walCheckpoint.go`)\n\nAdd `var walCheckpointActive atomic.Bool` at ~line 100, next to `walShuttingDown`.\n\n### 2. Skip WAL sends during checkpoint (`walCheckpoint.go:SendWALMessage`)\n\nAdd early return `true` (not `false` — data is safe in memory) when `walCheckpointActive.Load()` is set. This prevents channel pressure AND avoids incrementing `walDropped`.\n\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n // ... existing select/send logic\n}\n```\n\n### 3. Remove direct WAL deletion race in `ToCheckpointWAL` (`walCheckpoint.go:730-733`)\n\nRemove the `os.Remove(walPath)` inside the checkpoint worker loop. This races with the WAL staging goroutine that still has the file open. `RotateWALFiles` (called afterward from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate`.\n\n### 4. Set/clear flag around checkpoint (`checkpoint.go:~128-139`)\n\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ... existing success handling ...\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false) // Always clear, even on error\n walDropped.Store(0) // Reset drop counter\n}\n```\n\n## Files to modify\n\n- `pkg/metricstore/walCheckpoint.go` — add flag, modify `SendWALMessage`, remove direct WAL delete\n- `pkg/metricstore/checkpoint.go` — set/clear flag around checkpoint call\n- `pkg/metricstore/lineprotocol.go` — no changes needed (`walDropped` is already exported)\n\n## Crash safety\n\nNo regression. During the checkpoint window:\n- Pre-existing WAL files remain on disk until `RotateWALFiles` (after all snapshots succeed)\n- New metrics are still written to in-memory store (`WriteToLevel` at line 373 runs regardless)\n- If crash mid-checkpoint: restart loads latest complete `.bin` + replays old `current.wal` — no data loss since snapshots use atomic rename (`.bin.tmp` → `.bin`)\n\n## Verification\n\n1. `go build ./...` — compiles\n2. `go test ./pkg/metricstore/...` — existing tests pass\n3. Deploy and confirm no more \"WAL shard channel full, dropped N messages\" warnings during checkpoint\n4. Confirm checkpoint logs show normal \"Starting binary checkpoint\" → \"done: N binary snapshot files created\" without drops\n","structuredPatch":[],"originalFile":null},"sourceToolAssistantUUID":"606423c2-3cb9-4899-868b-9fc576c35528","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"f29d974f-6bd0-44d4-8ba2-c87b5d355b6a","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_019yXsDpUDCp9yxp5Fxm153R","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01QaRneGWY2z5kSaSyhphz9x","name":"ToolSearch","input":{"query":"select:ExitPlanMode","max_results":1},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":1056,"cache_read_input_tokens":49518,"output_tokens":78,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":1056,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7QfMqVH6haEYL3xHMy","type":"assistant","uuid":"2873787b-22d6-4541-947b-1390a05ffee0","timestamp":"2026-03-29T09:10:34.483Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"2873787b-22d6-4541-947b-1390a05ffee0","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"type":"tool_result","tool_use_id":"toolu_01QaRneGWY2z5kSaSyhphz9x","content":[{"type":"tool_reference","tool_name":"ExitPlanMode"}]}]},"uuid":"cdb92408-a2a1-4aab-b145-483fb4a1aa35","timestamp":"2026-03-29T09:10:34.484Z","toolUseResult":{"matches":["ExitPlanMode"],"query":"select:ExitPlanMode","total_deferred_tools":22},"sourceToolAssistantUUID":"2873787b-22d6-4541-947b-1390a05ffee0","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"cdb92408-a2a1-4aab-b145-483fb4a1aa35","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01Emdr3RjjhNWJpb79Jk2Awd","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_018EsvnQdAKvYaP42AefMMC3","name":"ExitPlanMode","input":{"allowedPrompts":[{"tool":"Bash","prompt":"run go build"},{"tool":"Bash","prompt":"run go tests"}],"plan":"# Fix: WAL shard channel saturation during binary checkpoint\n\n## Context\n\nDuring periodic binary checkpoints (~every 12h), 1.44M+ WAL messages are dropped because shard channels fill up. The checkpoint processes 1845 hosts with 10 workers, taking ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint binary writes.\n\n**Key insight:** WAL writes during checkpoint are completely redundant — the binary snapshot reads directly from the in-memory Level tree, capturing everything. After the snapshot, WAL files are rotated (deleted). Any WAL records written during this window are immediately discarded.\n\n## Changes\n\n### 1. Add `walCheckpointActive` atomic flag (`walCheckpoint.go`)\n\nAdd `var walCheckpointActive atomic.Bool` at ~line 100, next to `walShuttingDown`.\n\n### 2. Skip WAL sends during checkpoint (`walCheckpoint.go:SendWALMessage`)\n\nAdd early return `true` (not `false` — data is safe in memory) when `walCheckpointActive.Load()` is set. This prevents channel pressure AND avoids incrementing `walDropped`.\n\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n // ... existing select/send logic\n}\n```\n\n### 3. Remove direct WAL deletion race in `ToCheckpointWAL` (`walCheckpoint.go:730-733`)\n\nRemove the `os.Remove(walPath)` inside the checkpoint worker loop. This races with the WAL staging goroutine that still has the file open. `RotateWALFiles` (called afterward from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate`.\n\n### 4. Set/clear flag around checkpoint (`checkpoint.go:~128-139`)\n\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ... existing success handling ...\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false) // Always clear, even on error\n walDropped.Store(0) // Reset drop counter\n}\n```\n\n## Files to modify\n\n- `pkg/metricstore/walCheckpoint.go` — add flag, modify `SendWALMessage`, remove direct WAL delete\n- `pkg/metricstore/checkpoint.go` — set/clear flag around checkpoint call\n- `pkg/metricstore/lineprotocol.go` — no changes needed (`walDropped` is already exported)\n\n## Crash safety\n\nNo regression. During the checkpoint window:\n- Pre-existing WAL files remain on disk until `RotateWALFiles` (after all snapshots succeed)\n- New metrics are still written to in-memory store (`WriteToLevel` at line 373 runs regardless)\n- If crash mid-checkpoint: restart loads latest complete `.bin` + replays old `current.wal` — no data loss since snapshots use atomic rename (`.bin.tmp` → `.bin`)\n\n## Verification\n\n1. `go build ./...` — compiles\n2. `go test ./pkg/metricstore/...` — existing tests pass\n3. Deploy and confirm no more \"WAL shard channel full, dropped N messages\" warnings during checkpoint\n4. Confirm checkpoint logs show normal \"Starting binary checkpoint\" → \"done: N binary snapshot files created\" without drops\n","planFilePath":"/Users/jan/.claude/plans/lovely-soaring-snail.md"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":738,"cache_read_input_tokens":50574,"output_tokens":91,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":738,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7Qw7d1Vp34UT8qF8nM","type":"assistant","uuid":"f859ccbc-65f9-4a3c-88e8-cde5d23b6d8e","timestamp":"2026-03-29T09:10:39.459Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"f859ccbc-65f9-4a3c-88e8-cde5d23b6d8e","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"type":"tool_result","content":"User has approved your plan. You can now start coding. Start with updating your todo list if applicable\n\nYour plan has been saved to: /Users/jan/.claude/plans/lovely-soaring-snail.md\nYou can refer back to it if needed during implementation.\n\n## Approved Plan:\n# Fix: WAL shard channel saturation during binary checkpoint\n\n## Context\n\nDuring periodic binary checkpoints (~every 12h), 1.44M+ WAL messages are dropped because shard channels fill up. The checkpoint processes 1845 hosts with 10 workers, taking ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint binary writes.\n\n**Key insight:** WAL writes during checkpoint are completely redundant — the binary snapshot reads directly from the in-memory Level tree, capturing everything. After the snapshot, WAL files are rotated (deleted). Any WAL records written during this window are immediately discarded.\n\n## Changes\n\n### 1. Add `walCheckpointActive` atomic flag (`walCheckpoint.go`)\n\nAdd `var walCheckpointActive atomic.Bool` at ~line 100, next to `walShuttingDown`.\n\n### 2. Skip WAL sends during checkpoint (`walCheckpoint.go:SendWALMessage`)\n\nAdd early return `true` (not `false` — data is safe in memory) when `walCheckpointActive.Load()` is set. This prevents channel pressure AND avoids incrementing `walDropped`.\n\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n // ... existing select/send logic\n}\n```\n\n### 3. Remove direct WAL deletion race in `ToCheckpointWAL` (`walCheckpoint.go:730-733`)\n\nRemove the `os.Remove(walPath)` inside the checkpoint worker loop. This races with the WAL staging goroutine that still has the file open. `RotateWALFiles` (called afterward from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate`.\n\n### 4. Set/clear flag around checkpoint (`checkpoint.go:~128-139`)\n\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ... existing success handling ...\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false) // Always clear, even on error\n walDropped.Store(0) // Reset drop counter\n}\n```\n\n## Files to modify\n\n- `pkg/metricstore/walCheckpoint.go` — add flag, modify `SendWALMessage`, remove direct WAL delete\n- `pkg/metricstore/checkpoint.go` — set/clear flag around checkpoint call\n- `pkg/metricstore/lineprotocol.go` — no changes needed (`walDropped` is already exported)\n\n## Crash safety\n\nNo regression. During the checkpoint window:\n- Pre-existing WAL files remain on disk until `RotateWALFiles` (after all snapshots succeed)\n- New metrics are still written to in-memory store (`WriteToLevel` at line 373 runs regardless)\n- If crash mid-checkpoint: restart loads latest complete `.bin` + replays old `current.wal` — no data loss since snapshots use atomic rename (`.bin.tmp` → `.bin`)\n\n## Verification\n\n1. `go build ./...` — compiles\n2. `go test ./pkg/metricstore/...` — existing tests pass\n3. Deploy and confirm no more \"WAL shard channel full, dropped N messages\" warnings during checkpoint\n4. Confirm checkpoint logs show normal \"Starting binary checkpoint\" → \"done: N binary snapshot files created\" without drops\n","tool_use_id":"toolu_018EsvnQdAKvYaP42AefMMC3"}]},"uuid":"f0cb6989-957a-4137-9569-bb719befb3e9","timestamp":"2026-03-29T09:11:53.092Z","toolUseResult":{"plan":"# Fix: WAL shard channel saturation during binary checkpoint\n\n## Context\n\nDuring periodic binary checkpoints (~every 12h), 1.44M+ WAL messages are dropped because shard channels fill up. The checkpoint processes 1845 hosts with 10 workers, taking ~12+ seconds. During this time, incoming metrics keep arriving but WAL staging goroutines can't keep up due to disk I/O contention from checkpoint binary writes.\n\n**Key insight:** WAL writes during checkpoint are completely redundant — the binary snapshot reads directly from the in-memory Level tree, capturing everything. After the snapshot, WAL files are rotated (deleted). Any WAL records written during this window are immediately discarded.\n\n## Changes\n\n### 1. Add `walCheckpointActive` atomic flag (`walCheckpoint.go`)\n\nAdd `var walCheckpointActive atomic.Bool` at ~line 100, next to `walShuttingDown`.\n\n### 2. Skip WAL sends during checkpoint (`walCheckpoint.go:SendWALMessage`)\n\nAdd early return `true` (not `false` — data is safe in memory) when `walCheckpointActive.Load()` is set. This prevents channel pressure AND avoids incrementing `walDropped`.\n\n```go\nfunc SendWALMessage(msg *WALMessage) bool {\n if walShardChs == nil || walShuttingDown.Load() {\n return false\n }\n if walCheckpointActive.Load() {\n return true // Data safe in memory; snapshot will capture it\n }\n // ... existing select/send logic\n}\n```\n\n### 3. Remove direct WAL deletion race in `ToCheckpointWAL` (`walCheckpoint.go:730-733`)\n\nRemove the `os.Remove(walPath)` inside the checkpoint worker loop. This races with the WAL staging goroutine that still has the file open. `RotateWALFiles` (called afterward from `checkpoint.go:139`) already handles deletion properly through the staging goroutine's `processRotate`.\n\n### 4. Set/clear flag around checkpoint (`checkpoint.go:~128-139`)\n\n```go\nif Keys.Checkpoints.FileFormat == \"wal\" {\n walCheckpointActive.Store(true)\n n, hostDirs, err := ms.ToCheckpointWAL(...)\n if err != nil {\n cclog.Errorf(...)\n }\n if n > 0 {\n // ... existing success handling ...\n RotateWALFiles(hostDirs)\n }\n walCheckpointActive.Store(false) // Always clear, even on error\n walDropped.Store(0) // Reset drop counter\n}\n```\n\n## Files to modify\n\n- `pkg/metricstore/walCheckpoint.go` — add flag, modify `SendWALMessage`, remove direct WAL delete\n- `pkg/metricstore/checkpoint.go` — set/clear flag around checkpoint call\n- `pkg/metricstore/lineprotocol.go` — no changes needed (`walDropped` is already exported)\n\n## Crash safety\n\nNo regression. During the checkpoint window:\n- Pre-existing WAL files remain on disk until `RotateWALFiles` (after all snapshots succeed)\n- New metrics are still written to in-memory store (`WriteToLevel` at line 373 runs regardless)\n- If crash mid-checkpoint: restart loads latest complete `.bin` + replays old `current.wal` — no data loss since snapshots use atomic rename (`.bin.tmp` → `.bin`)\n\n## Verification\n\n1. `go build ./...` — compiles\n2. `go test ./pkg/metricstore/...` — existing tests pass\n3. Deploy and confirm no more \"WAL shard channel full, dropped N messages\" warnings during checkpoint\n4. Confirm checkpoint logs show normal \"Starting binary checkpoint\" → \"done: N binary snapshot files created\" without drops\n","isAgent":false,"filePath":"/Users/jan/.claude/plans/lovely-soaring-snail.md"},"sourceToolAssistantUUID":"f859ccbc-65f9-4a3c-88e8-cde5d23b6d8e","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"type":"custom-title","customTitle":"wal-shard-saturation-checkpoint","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74"} {"type":"agent-name","agentName":"wal-shard-saturation-checkpoint","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74"} {"parentUuid":"f0cb6989-957a-4137-9569-bb719befb3e9","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01PfKYggq8qbvcc4euadauxS","type":"message","role":"assistant","content":[{"type":"text","text":"Let me implement the changes.\n\n**Step 1: Add `walCheckpointActive` flag and modify `SendWALMessage`** in `walCheckpoint.go`:"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":1160,"cache_read_input_tokens":51312,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":1160},"output_tokens":1,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7WjGtsKKP9afnBm5kz","type":"assistant","uuid":"d15dba98-07db-4427-b845-1d394ec7578b","timestamp":"2026-03-29T09:11:56.440Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"d15dba98-07db-4427-b845-1d394ec7578b","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01PfKYggq8qbvcc4euadauxS","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01R9JDgEfx12SvL1gr61VbbP","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","old_string":"// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool","new_string":"// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool\n\n// walCheckpointActive is set during binary checkpoint writes.\n// While active, SendWALMessage skips sending (returns true) because the\n// snapshot captures all in-memory data, making WAL writes redundant.\nvar walCheckpointActive atomic.Bool"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":1160,"cache_read_input_tokens":51312,"output_tokens":307,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":1160,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7WjGtsKKP9afnBm5kz","type":"assistant","uuid":"cd5c0e09-d58b-4a57-b2bc-9e0aaca2b2a7","timestamp":"2026-03-29T09:11:59.756Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"type":"file-history-snapshot","messageId":"cd5c0e09-d58b-4a57-b2bc-9e0aaca2b2a7","snapshot":{"messageId":"7fe64e31-f76e-403e-88ab-3a6e6ef368e7","trackedFileBackups":{"/Users/jan/.claude/plans/lovely-soaring-snail.md":{"backupFileName":null,"version":1,"backupTime":"2026-03-29T09:10:30.845Z"},"pkg/metricstore/walCheckpoint.go":{"backupFileName":"f5b5b4bac0274f50@v1","version":1,"backupTime":"2026-03-29T09:11:59.778Z"}},"timestamp":"2026-03-29T09:04:51.569Z"},"isSnapshotUpdate":true} {"parentUuid":"cd5c0e09-d58b-4a57-b2bc-9e0aaca2b2a7","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01R9JDgEfx12SvL1gr61VbbP","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"61f3167b-1fca-43ae-987d-1a1932920216","timestamp":"2026-03-29T09:11:59.782Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool","newString":"// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool\n\n// walCheckpointActive is set during binary checkpoint writes.\n// While active, SendWALMessage skips sending (returns true) because the\n// snapshot captures all in-memory data, making WAL writes redundant.\nvar walCheckpointActive atomic.Bool","originalFile":"// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.\n// All rights reserved. This file is part of cc-backend.\n// Use of this source code is governed by a MIT-style\n// license that can be found in the LICENSE file.\n\n// Package metricstore provides walCheckpoint.go: WAL-based checkpoint implementation.\n//\n// This replaces the Avro shadow tree with an append-only Write-Ahead Log (WAL)\n// per host, eliminating the extra memory overhead of the AvroStore and providing\n// truly continuous (per-write) crash safety.\n//\n// # Architecture\n//\n//\tMetric write (DecodeLine)\n//\t │\n//\t ├─► WriteToLevel() → main MemoryStore (unchanged)\n//\t │\n//\t └─► WALMessages channel\n//\t │\n//\t ▼\n//\t WALStaging goroutine\n//\t │\n//\t ▼\n//\t checkpoints/cluster/host/current.wal (append-only, binary)\n//\n//\tPeriodic checkpoint (Checkpointing goroutine):\n//\t 1. Write .bin snapshot (column-oriented, from main tree)\n//\t 2. Signal WALStaging to truncate current.wal per host\n//\n//\tOn restart (FromCheckpoint):\n//\t 1. Load most recent .bin snapshot\n//\t 2. Replay current.wal (overwrite-safe: buffer.write handles duplicate timestamps)\n//\n// # WAL Record Format\n//\n//\t[4B magic 0xCC1DA7A1][4B payload_len][payload][4B CRC32]\n//\n//\tpayload:\n//\t [8B timestamp int64]\n//\t [2B metric_name_len uint16][N metric name bytes]\n//\t [1B selector_count uint8]\n//\t per selector: [1B selector_len uint8][M selector bytes]\n//\t [4B value float32 bits]\n//\n// # Binary Snapshot Format\n//\n//\t[4B magic 0xCC5B0001][8B from int64][8B to int64]\n//\tLevel tree (recursive):\n//\t [4B num_metrics uint32]\n//\t per metric:\n//\t [2B name_len uint16][N name bytes]\n//\t [8B frequency int64][8B start int64]\n//\t [4B num_values uint32][num_values × 4B float32]\n//\t [4B num_children uint32]\n//\t per child: [2B name_len uint16][N name bytes] + Level (recursive)\npackage metricstore\n\nimport (\n\t\"bufio\"\n\t\"context\"\n\t\"encoding/binary\"\n\t\"fmt\"\n\t\"hash/crc32\"\n\t\"hash/fnv\"\n\t\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\n\t\"time\"\n\n\tcclog \"github.com/ClusterCockpit/cc-lib/v2/ccLogger\"\n\t\"github.com/ClusterCockpit/cc-lib/v2/schema\"\n)\n\n// Magic numbers for binary formats.\nconst (\n\twalFileMagic = uint32(0xCC1DA701) // WAL file header magic\n\twalRecordMagic = uint32(0xCC1DA7A1) // WAL record magic\n\tsnapFileMagic = uint32(0xCC5B0001) // Binary snapshot magic\n)\n\n// walShardChs holds per-shard channels for WAL messages.\n// Initialized by WALStaging; nil when WAL is not active.\nvar walShardChs []chan *WALMessage\n\n// walShardRotateChs holds per-shard channels for WAL rotation requests.\nvar walShardRotateChs []chan walRotateReq\n\n// walNumShards stores the number of shards (set during WALStaging init).\nvar walNumShards int\n\n// walStagingWg tracks WALStaging goroutine exits for shutdown synchronization.\nvar walStagingWg sync.WaitGroup\n\n// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool\n\n// WALMessage represents a single metric write to be appended to the WAL.\n// Cluster and Node are NOT stored in the WAL record (inferred from file path).\ntype WALMessage struct {\n\tMetricName string\n\tCluster string\n\tNode string\n\tSelector []string\n\tValue schema.Float\n\tTimestamp int64\n}\n\n// walRotateReq requests WAL file rotation for a specific host directory.\n// The done channel is closed by the WAL goroutine when rotation is complete.\ntype walRotateReq struct {\n\thostDir string\n\tdone chan struct{}\n}\n\n// walFileState holds an open WAL file handle and buffered writer for one host directory.\ntype walFileState struct {\n\tf *os.File\n\tw *bufio.Writer\n\tdirty bool\n\tsize int64 // approximate bytes written (tracked from open + writes)\n}\n\n// walFlushInterval controls how often dirty WAL files are flushed to disk.\n// Decoupling flushes from message processing lets the consumer run at memory\n// speed, amortizing syscall overhead across many writes.\nconst walFlushInterval = 1 * time.Second\n\n// walShardIndex computes which shard a message belongs to based on cluster+node.\n// Uses FNV-1a hash for fast, well-distributed mapping.\nfunc walShardIndex(cluster, node string) int {\n\th := fnv.New32a()\n\th.Write([]byte(cluster))\n\th.Write([]byte{0})\n\th.Write([]byte(node))\n\treturn int(h.Sum32()) % walNumShards\n}\n\n// SendWALMessage routes a WAL message to the appropriate shard channel.\n// Returns false if the channel is full or shutdown is in progress.\nfunc SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}\n\n// WALStaging starts N sharded background goroutines that receive WALMessage items\n// and append binary WAL records to per-host current.wal files.\n// Each shard owns a subset of hosts (determined by hash of cluster+node),\n// parallelizing serialization and I/O while keeping per-host writes serial.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\treturn\n\t}\n\n\twalNumShards = max(Keys.NumWorkers, 1)\n\tchBufSize := max(65536/walNumShards, 1024)\n\n\twalShardChs = make([]chan *WALMessage, walNumShards)\n\twalShardRotateChs = make([]chan walRotateReq, walNumShards)\n\n\tfor i := range walNumShards {\n\t\twalShardChs[i] = make(chan *WALMessage, chBufSize)\n\t\twalShardRotateChs[i] = make(chan walRotateReq, 64)\n\t}\n\n\tfor i := range walNumShards {\n\t\tmsgCh := walShardChs[i]\n\t\trotateCh := walShardRotateChs[i]\n\n\t\twalStagingWg.Add(1)\n\t\twg.Go(func() {\n\t\t\tdefer walStagingWg.Done()\n\t\t\thostFiles := make(map[string]*walFileState)\n\n\t\t\tdefer func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.f != nil {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.f.Close()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}()\n\n\t\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\t\tws, ok := hostFiles[hostDir]\n\t\t\t\tif ok {\n\t\t\t\t\treturn ws\n\t\t\t\t}\n\n\t\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t\t// Write file header magic if file is new (empty).\n\t\t\t\tinfo, err := f.Stat()\n\t\t\t\tvar fileSize int64\n\t\t\t\tif err == nil {\n\t\t\t\t\tfileSize = info.Size()\n\t\t\t\t}\n\t\t\t\tif err == nil && fileSize == 0 {\n\t\t\t\t\tvar hdr [4]byte\n\t\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\t\tf.Close()\n\t\t\t\t\t\treturn nil\n\t\t\t\t\t}\n\t\t\t\t\tfileSize = 4\n\t\t\t\t}\n\n\t\t\t\tws = &walFileState{f: f, w: w, size: fileSize}\n\t\t\t\thostFiles[hostDir] = ws\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\t\tif ws == nil {\n\t\t\t\t\treturn\n\t\t\t\t}\n\n\t\t\t\t// Enforce max WAL size: force-rotate before writing if limit is exceeded.\n\t\t\t\t// The in-memory store still holds the data; only crash-recovery coverage is lost.\n\t\t\t\tif maxSize := Keys.Checkpoints.MaxWALSize; maxSize > 0 && ws.size >= maxSize {\n\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL: force-rotating %s (size %d >= limit %d)\",\n\t\t\t\t\t\thostDir, ws.size, maxSize)\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, hostDir)\n\t\t\t\t\tws = getOrOpenWAL(hostDir)\n\t\t\t\t\tif ws == nil {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t}\n\n\t\t\t\tn, err := writeWALRecordDirect(ws.w, msg)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t\t}\n\t\t\t\tws.size += int64(n)\n\t\t\t\tws.dirty = true\n\t\t\t}\n\n\t\t\tprocessRotate := func(req walRotateReq) {\n\t\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\t\tif ok && ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t\t}\n\t\t\t\tclose(req.done)\n\t\t\t}\n\n\t\t\tflushDirty := func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.dirty {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.dirty = false\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tticker := time.NewTicker(walFlushInterval)\n\t\t\tdefer ticker.Stop()\n\n\t\t\t// drainBatch processes up to 4096 pending messages without blocking.\n\t\t\t// Returns false if the channel was closed.\n\t\t\tdrainBatch := func() bool {\n\t\t\t\tfor range 4096 {\n\t\t\t\t\tselect {\n\t\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\t\tif !ok {\n\t\t\t\t\t\t\tflushDirty()\n\t\t\t\t\t\t\treturn false\n\t\t\t\t\t\t}\n\t\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\t\tprocessRotate(req)\n\t\t\t\t\tdefault:\n\t\t\t\t\t\treturn true\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\treturn true\n\t\t\t}\n\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase <-ctx.Done():\n\t\t\t\t\t// On shutdown, skip draining buffered messages — a full binary\n\t\t\t\t\t// checkpoint will be written from in-memory state, making\n\t\t\t\t\t// buffered WAL records redundant.\n\t\t\t\t\tflushDirty()\n\t\t\t\t\treturn\n\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\tif !ok {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tif !drainBatch() {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\t// No flush here — timer handles periodic flushing.\n\t\t\t\tcase <-ticker.C:\n\t\t\t\t\tflushDirty()\n\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\t}\n\t\t\t}\n\t\t})\n\t}\n}\n\n// WaitForWALStagingDrain blocks until all WALStaging goroutines have exited.\n// Must be called after closing walShardChs to ensure all file handles are\n// flushed and closed before checkpoint writes begin.\nfunc WaitForWALStagingDrain() {\n\twalStagingWg.Wait()\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete. Each request is routed to the\n// shard that owns the host directory.\n//\n// If shutdown is in progress (WAL staging goroutines may have exited),\n// rotation is skipped to avoid deadlocking on abandoned channels.\nfunc RotateWALFiles(hostDirs []string) {\n\tif walShardRotateChs == nil || walShuttingDown.Load() {\n\t\treturn\n\t}\n\tdeadline := time.After(2 * time.Minute)\n\tdones := make([]chan struct{}, 0, len(hostDirs))\n\tfor _, dir := range hostDirs {\n\t\tdone := make(chan struct{})\n\t\tshard := walShardIndexFromDir(dir)\n\t\tselect {\n\t\tcase walShardRotateChs[shard] <- walRotateReq{hostDir: dir, done: done}:\n\t\t\tdones = append(dones, done)\n\t\tcase <-deadline:\n\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL rotation send timed out, %d of %d hosts remaining\",\n\t\t\t\tlen(hostDirs)-len(dones), len(hostDirs))\n\t\t\tgoto waitDones\n\t\t}\n\t}\nwaitDones:\n\tfor _, done := range dones {\n\t\tselect {\n\t\tcase <-done:\n\t\tcase <-time.After(30 * time.Second):\n\t\t\tcclog.Warn(\"[METRICSTORE]> WAL rotation completion timed out, continuing\")\n\t\t\treturn\n\t\t}\n\t}\n}\n\n// walShardIndexFromDir extracts cluster and node from a host directory path\n// and returns the shard index. The path format is: rootDir/cluster/node\nfunc walShardIndexFromDir(hostDir string) int {\n\t// hostDir = .../cluster/node — extract last two path components\n\tnode := path.Base(hostDir)\n\tcluster := path.Base(path.Dir(hostDir))\n\treturn walShardIndex(cluster, node)\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFilesAfterShutdown(hostDirs []string) {\n\tfor _, dir := range hostDirs {\n\t\twalPath := path.Join(dir, \"current.wal\")\n\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t}\n\t}\n}\n\n// writeWALRecordDirect encodes a WAL record into a contiguous buffer first,\n// then writes it to the bufio.Writer in a single call. This prevents partial\n// records in the write buffer if a write error occurs mid-record (e.g. disk full).\n// Returns the number of bytes written and any error.\nfunc writeWALRecordDirect(w *bufio.Writer, msg *WALMessage) (int, error) {\n\t// Compute payload and total record size.\n\tpayloadSize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tpayloadSize += 1 + len(s)\n\t}\n\t// Total: 8 (header) + payload + 4 (CRC).\n\ttotalSize := 8 + payloadSize + 4\n\n\t// Use stack buffer for typical small records, heap-allocate only for large ones.\n\tvar stackBuf [256]byte\n\tvar buf []byte\n\tif totalSize <= len(stackBuf) {\n\t\tbuf = stackBuf[:totalSize]\n\t} else {\n\t\tbuf = make([]byte, totalSize)\n\t}\n\n\t// Header: magic + payload length.\n\tbinary.LittleEndian.PutUint32(buf[0:4], walRecordMagic)\n\tbinary.LittleEndian.PutUint32(buf[4:8], uint32(payloadSize))\n\n\t// Payload starts at offset 8.\n\tp := 8\n\n\t// Timestamp (8 bytes).\n\tbinary.LittleEndian.PutUint64(buf[p:p+8], uint64(msg.Timestamp))\n\tp += 8\n\n\t// Metric name length (2 bytes) + metric name.\n\tbinary.LittleEndian.PutUint16(buf[p:p+2], uint16(len(msg.MetricName)))\n\tp += 2\n\tp += copy(buf[p:], msg.MetricName)\n\n\t// Selector count (1 byte).\n\tbuf[p] = byte(len(msg.Selector))\n\tp++\n\n\t// Selectors (1-byte length + bytes each).\n\tfor _, sel := range msg.Selector {\n\t\tbuf[p] = byte(len(sel))\n\t\tp++\n\t\tp += copy(buf[p:], sel)\n\t}\n\n\t// Value (4 bytes, float32 bits).\n\tbinary.LittleEndian.PutUint32(buf[p:p+4], math.Float32bits(float32(msg.Value)))\n\tp += 4\n\n\t// CRC32 over payload (bytes 8..8+payloadSize).\n\tcrc := crc32.ChecksumIEEE(buf[8 : 8+payloadSize])\n\tbinary.LittleEndian.PutUint32(buf[p:p+4], crc)\n\n\t// Single atomic write to the buffered writer.\n\tn, err := w.Write(buf)\n\treturn n, err\n}\n\n// readWALRecord reads one WAL record from the reader.\n// Returns (nil, nil) on clean EOF. Returns error on data corruption.\n// A CRC mismatch indicates a truncated trailing record (expected on crash).\nfunc readWALRecord(r io.Reader) (*WALMessage, error) {\n\tvar magic uint32\n\tif err := binary.Read(r, binary.LittleEndian, &magic); err != nil {\n\t\tif err == io.EOF {\n\t\t\treturn nil, nil // Clean EOF\n\t\t}\n\t\treturn nil, fmt.Errorf(\"read record magic: %w\", err)\n\t}\n\n\tif magic != walRecordMagic {\n\t\treturn nil, fmt.Errorf(\"invalid record magic 0x%08X (expected 0x%08X)\", magic, walRecordMagic)\n\t}\n\n\tvar payloadLen uint32\n\tif err := binary.Read(r, binary.LittleEndian, &payloadLen); err != nil {\n\t\treturn nil, fmt.Errorf(\"read payload length: %w\", err)\n\t}\n\n\tif payloadLen > 1<<20 { // 1 MB sanity limit\n\t\treturn nil, fmt.Errorf(\"record payload too large: %d bytes\", payloadLen)\n\t}\n\n\tpayload := make([]byte, payloadLen)\n\tif _, err := io.ReadFull(r, payload); err != nil {\n\t\treturn nil, fmt.Errorf(\"read payload: %w\", err)\n\t}\n\n\tvar storedCRC uint32\n\tif err := binary.Read(r, binary.LittleEndian, &storedCRC); err != nil {\n\t\treturn nil, fmt.Errorf(\"read CRC: %w\", err)\n\t}\n\n\tif crc32.ChecksumIEEE(payload) != storedCRC {\n\t\treturn nil, fmt.Errorf(\"CRC mismatch (truncated write or corruption)\")\n\t}\n\n\treturn parseWALPayload(payload)\n}\n\n// parseWALPayload decodes a binary payload into a WALMessage.\nfunc parseWALPayload(payload []byte) (*WALMessage, error) {\n\tif len(payload) < 8+2+1+4 {\n\t\treturn nil, fmt.Errorf(\"payload too short: %d bytes\", len(payload))\n\t}\n\n\toffset := 0\n\n\t// Timestamp (8 bytes)\n\tts := int64(binary.LittleEndian.Uint64(payload[offset : offset+8]))\n\toffset += 8\n\n\t// Metric name (2-byte length + bytes)\n\tif offset+2 > len(payload) {\n\t\treturn nil, fmt.Errorf(\"metric name length overflows payload\")\n\t}\n\tmLen := int(binary.LittleEndian.Uint16(payload[offset : offset+2]))\n\toffset += 2\n\n\tif offset+mLen > len(payload) {\n\t\treturn nil, fmt.Errorf(\"metric name overflows payload\")\n\t}\n\tmetricName := string(payload[offset : offset+mLen])\n\toffset += mLen\n\n\t// Selector count (1 byte)\n\tif offset >= len(payload) {\n\t\treturn nil, fmt.Errorf(\"selector count overflows payload\")\n\t}\n\tselCount := int(payload[offset])\n\toffset++\n\n\tselectors := make([]string, selCount)\n\tfor i := range selCount {\n\t\tif offset >= len(payload) {\n\t\t\treturn nil, fmt.Errorf(\"selector[%d] length overflows payload\", i)\n\t\t}\n\t\tsLen := int(payload[offset])\n\t\toffset++\n\n\t\tif offset+sLen > len(payload) {\n\t\t\treturn nil, fmt.Errorf(\"selector[%d] data overflows payload\", i)\n\t\t}\n\t\tselectors[i] = string(payload[offset : offset+sLen])\n\t\toffset += sLen\n\t}\n\n\t// Value (4 bytes, float32 bits)\n\tif offset+4 > len(payload) {\n\t\treturn nil, fmt.Errorf(\"value overflows payload\")\n\t}\n\tbits := binary.LittleEndian.Uint32(payload[offset : offset+4])\n\tvalue := schema.Float(math.Float32frombits(bits))\n\n\treturn &WALMessage{\n\t\tMetricName: metricName,\n\t\tTimestamp: ts,\n\t\tSelector: selectors,\n\t\tValue: value,\n\t}, nil\n}\n\n// loadWALFile reads a WAL file and replays all valid records into the Level tree.\n// l is the host-level node. Corrupt or partial trailing records are silently skipped\n// (expected on crash). Records older than 'from' are skipped.\nfunc (l *Level) loadWALFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\n\t// Verify file header magic.\n\tvar fileMagic uint32\n\tif err := binary.Read(br, binary.LittleEndian, &fileMagic); err != nil {\n\t\tif err == io.EOF {\n\t\t\treturn nil // Empty file, no data\n\t\t}\n\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: read file header: %w\", err)\n\t}\n\n\tif fileMagic != walFileMagic {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: invalid file magic 0x%08X (expected 0x%08X)\", fileMagic, walFileMagic)\n\t}\n\n\t// Cache level lookups to avoid repeated tree traversal.\n\tlvlCache := make(map[string]*Level)\n\n\tfor {\n\t\tmsg, err := readWALRecord(br)\n\t\tif err != nil {\n\t\t\t// Truncated trailing record is expected after a crash; stop replaying.\n\t\t\tcclog.Debugf(\"[METRICSTORE]> WAL: stopping replay at corrupted/partial record: %v\", err)\n\t\t\tbreak\n\t\t}\n\t\tif msg == nil {\n\t\t\tbreak // Clean EOF\n\t\t}\n\n\t\tif msg.Timestamp < from {\n\t\t\tcontinue // Older than retention window\n\t\t}\n\n\t\tminfo, ok := m.Metrics[msg.MetricName]\n\t\tif !ok {\n\t\t\tcontinue // Unknown metric (config may have changed)\n\t\t}\n\n\t\t// Cache key is the null-separated selector path.\n\t\tcacheKey := joinSelector(msg.Selector)\n\t\tlvl, ok := lvlCache[cacheKey]\n\t\tif !ok {\n\t\t\tlvl = l.findLevelOrCreate(msg.Selector, len(m.Metrics))\n\t\t\tlvlCache[cacheKey] = lvl\n\t\t}\n\n\t\t// Write directly to the buffer, same as WriteToLevel but without the\n\t\t// global level lookup (we already have the right level).\n\t\tlvl.lock.Lock()\n\t\tb := lvl.metrics[minfo.offset]\n\t\tif b == nil {\n\t\t\tb = newBuffer(msg.Timestamp, minfo.Frequency)\n\t\t\tlvl.metrics[minfo.offset] = b\n\t\t}\n\t\tnb, writeErr := b.write(msg.Timestamp, msg.Value)\n\t\tif writeErr == nil && b != nb {\n\t\t\tlvl.metrics[minfo.offset] = nb\n\t\t}\n\t\t// Ignore write errors for timestamps before buffer start (can happen when\n\t\t// replaying WAL entries that predate a loaded snapshot's start time).\n\t\tlvl.lock.Unlock()\n\t}\n\n\treturn nil\n}\n\n// joinSelector builds a cache key from a selector slice using null bytes as separators.\nfunc joinSelector(sel []string) string {\n\tif len(sel) == 0 {\n\t\treturn \"\"\n\t}\n\tvar result strings.Builder\n\tresult.WriteString(sel[0])\n\tfor i := 1; i < len(sel); i++ {\n\t\tresult.WriteString(\"\\x00\" + sel[i])\n\t}\n\treturn result.String()\n}\n\n// ToCheckpointWAL writes binary snapshot files for all hosts in parallel.\n// Returns the number of files written, the list of host directories that were\n// successfully checkpointed (for WAL rotation), and any errors.\nfunc (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string, error) {\n\t// Collect all cluster/host pairs.\n\tm.root.lock.RLock()\n\ttotalHosts := 0\n\tfor _, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\ttotalHosts += len(l1.children)\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\tlevels := make([]*Level, 0, totalHosts)\n\tselectors := make([][]string, 0, totalHosts)\n\n\tm.root.lock.RLock()\n\tfor sel1, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\tfor sel2, l2 := range l1.children {\n\t\t\tlevels = append(levels, l2)\n\t\t\tselectors = append(selectors, []string{sel1, sel2})\n\t\t}\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\ttype workItem struct {\n\t\tlevel *Level\n\t\thostDir string\n\t\tselector []string\n\t}\n\n\ttotalWork := len(levels)\n\tcclog.Infof(\"[METRICSTORE]> Starting binary checkpoint for %d hosts with %d workers\", totalWork, Keys.NumWorkers)\n\n\tn, errs, completed := int32(0), int32(0), int32(0)\n\tvar successDirs []string\n\tvar successMu sync.Mutex\n\n\tvar wg sync.WaitGroup\n\twg.Add(Keys.NumWorkers)\n\twork := make(chan workItem, Keys.NumWorkers*2)\n\n\t// Progress logging goroutine.\n\tstopProgress := make(chan struct{})\n\tgo func() {\n\t\tticker := time.NewTicker(10 * time.Second)\n\t\tdefer ticker.Stop()\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ticker.C:\n\t\t\t\tcclog.Infof(\"[METRICSTORE]> Checkpoint progress: %d/%d hosts (%d written, %d errors)\",\n\t\t\t\t\tatomic.LoadInt32(&completed), totalWork, atomic.LoadInt32(&n), atomic.LoadInt32(&errs))\n\t\t\tcase <-stopProgress:\n\t\t\t\treturn\n\t\t\t}\n\t\t}\n\t}()\n\n\tfor range Keys.NumWorkers {\n\t\tgo func() {\n\t\t\tdefer wg.Done()\n\t\t\tfor wi := range work {\n\t\t\t\terr := wi.level.toCheckpointBinary(wi.hostDir, from, to, m)\n\t\t\t\tif err != nil {\n\t\t\t\t\tif err == ErrNoNewArchiveData {\n\t\t\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t\t\t\tcontinue\n\t\t\t\t\t}\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpoint error for %s: %v\", wi.hostDir, err)\n\t\t\t\t\tatomic.AddInt32(&errs, 1)\n\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tsuccessMu.Lock()\n\t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n\t\t\t\t\tsuccessMu.Unlock()\n\t\t\t\t}\n\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t}\n\t\t}()\n\t}\n\n\tfor i := range levels {\n\t\thostDir := path.Join(dir, path.Join(selectors[i]...))\n\t\twork <- workItem{\n\t\t\tlevel: levels[i],\n\t\t\thostDir: hostDir,\n\t\t\tselector: selectors[i],\n\t\t}\n\t}\n\tclose(work)\n\twg.Wait()\n\tclose(stopProgress)\n\n\tif errs > 0 {\n\t\treturn int(n), successDirs, fmt.Errorf(\"[METRICSTORE]> %d errors during binary checkpoint (%d successes)\", errs, n)\n\t}\n\treturn int(n), successDirs, nil\n}\n\n// toCheckpointBinary writes a binary snapshot file for a single host-level node.\n// Uses atomic rename (write to .tmp then rename) to avoid partial reads on crash.\nfunc (l *Level) toCheckpointBinary(dir string, from, to int64, m *MemoryStore) error {\n\tcf, err := l.toCheckpointFile(from, to, m)\n\tif err != nil {\n\t\treturn err\n\t}\n\tif cf == nil {\n\t\treturn ErrNoNewArchiveData\n\t}\n\n\tif err := os.MkdirAll(dir, CheckpointDirPerms); err != nil {\n\t\treturn fmt.Errorf(\"mkdir %s: %w\", dir, err)\n\t}\n\n\t// Write to a temp file first, then rename (atomic on POSIX).\n\ttmpPath := path.Join(dir, fmt.Sprintf(\"%d.bin.tmp\", from))\n\tfinalPath := path.Join(dir, fmt.Sprintf(\"%d.bin\", from))\n\n\tf, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"open binary snapshot %s: %w\", tmpPath, err)\n\t}\n\n\tbw := bufio.NewWriter(f)\n\tif err := writeBinarySnapshotFile(bw, cf); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn fmt.Errorf(\"write binary snapshot: %w\", err)\n\t}\n\tif err := bw.Flush(); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn err\n\t}\n\tf.Close()\n\n\treturn os.Rename(tmpPath, finalPath)\n}\n\n// writeBinarySnapshotFile writes the binary snapshot file header and level tree.\nfunc writeBinarySnapshotFile(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, snapFileMagic); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.From); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.To); err != nil {\n\t\treturn err\n\t}\n\treturn writeBinaryLevel(w, cf)\n}\n\n// writeBinaryLevel recursively writes a CheckpointFile level in binary format.\nfunc writeBinaryLevel(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Metrics))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, metric := range cf.Metrics {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Frequency); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Start); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(metric.Data))); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tfor _, v := range metric.Data {\n\t\t\tif err := binary.Write(w, binary.LittleEndian, math.Float32bits(float32(v))); err != nil {\n\t\t\t\treturn err\n\t\t\t}\n\t\t}\n\t}\n\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Children))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, child := range cf.Children {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := writeBinaryLevel(w, child); err != nil {\n\t\t\treturn err\n\t\t}\n\t}\n\n\treturn nil\n}\n\n// writeString16 writes a 2-byte length-prefixed string to w.\nfunc writeString16(w io.Writer, s string) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint16(len(s))); err != nil {\n\t\treturn err\n\t}\n\t_, err := io.WriteString(w, s)\n\treturn err\n}\n\n// loadBinaryFile reads a binary snapshot file and loads data into the Level tree.\n// The retention check (from) is applied to the file's 'to' timestamp.\nfunc (l *Level) loadBinaryFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\n\tvar magic uint32\n\tif err := binary.Read(br, binary.LittleEndian, &magic); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read magic: %w\", err)\n\t}\n\tif magic != snapFileMagic {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: invalid magic 0x%08X (expected 0x%08X)\", magic, snapFileMagic)\n\t}\n\n\tvar fileFrom, fileTo int64\n\tif err := binary.Read(br, binary.LittleEndian, &fileFrom); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read from: %w\", err)\n\t}\n\tif err := binary.Read(br, binary.LittleEndian, &fileTo); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read to: %w\", err)\n\t}\n\n\tif fileTo != 0 && fileTo < from {\n\t\treturn nil // File is older than retention window, skip it\n\t}\n\n\tcf, err := readBinaryLevel(br)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read level tree: %w\", err)\n\t}\n\tcf.From = fileFrom\n\tcf.To = fileTo\n\n\treturn l.loadFile(cf, m)\n}\n\n// readBinaryLevel recursively reads a level from the binary snapshot format.\nfunc readBinaryLevel(r io.Reader) (*CheckpointFile, error) {\n\tcf := &CheckpointFile{\n\t\tMetrics: make(map[string]*CheckpointMetrics),\n\t\tChildren: make(map[string]*CheckpointFile),\n\t}\n\n\tvar numMetrics uint32\n\tif err := binary.Read(r, binary.LittleEndian, &numMetrics); err != nil {\n\t\treturn nil, fmt.Errorf(\"read num_metrics: %w\", err)\n\t}\n\n\tfor range numMetrics {\n\t\tname, err := readString16(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read metric name: %w\", err)\n\t\t}\n\n\t\tvar freq, start int64\n\t\tif err := binary.Read(r, binary.LittleEndian, &freq); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read frequency for %s: %w\", name, err)\n\t\t}\n\t\tif err := binary.Read(r, binary.LittleEndian, &start); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read start for %s: %w\", name, err)\n\t\t}\n\n\t\tvar numValues uint32\n\t\tif err := binary.Read(r, binary.LittleEndian, &numValues); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read num_values for %s: %w\", name, err)\n\t\t}\n\n\t\tdata := make([]schema.Float, numValues)\n\t\tfor i := range numValues {\n\t\t\tvar bits uint32\n\t\t\tif err := binary.Read(r, binary.LittleEndian, &bits); err != nil {\n\t\t\t\treturn nil, fmt.Errorf(\"read value[%d] for %s: %w\", i, name, err)\n\t\t\t}\n\t\t\tdata[i] = schema.Float(math.Float32frombits(bits))\n\t\t}\n\n\t\tcf.Metrics[name] = &CheckpointMetrics{\n\t\t\tFrequency: freq,\n\t\t\tStart: start,\n\t\t\tData: data,\n\t\t}\n\t}\n\n\tvar numChildren uint32\n\tif err := binary.Read(r, binary.LittleEndian, &numChildren); err != nil {\n\t\treturn nil, fmt.Errorf(\"read num_children: %w\", err)\n\t}\n\n\tfor range numChildren {\n\t\tchildName, err := readString16(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read child name: %w\", err)\n\t\t}\n\n\t\tchild, err := readBinaryLevel(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read child %s: %w\", childName, err)\n\t\t}\n\t\tcf.Children[childName] = child\n\t}\n\n\treturn cf, nil\n}\n\n// readString16 reads a 2-byte length-prefixed string from r.\nfunc readString16(r io.Reader) (string, error) {\n\tvar sLen uint16\n\tif err := binary.Read(r, binary.LittleEndian, &sLen); err != nil {\n\t\treturn \"\", err\n\t}\n\tbuf := make([]byte, sLen)\n\tif _, err := io.ReadFull(r, buf); err != nil {\n\t\treturn \"\", err\n\t}\n\treturn string(buf), nil\n}\n","structuredPatch":[{"oldStart":99,"oldLines":6,"newStart":99,"newLines":11,"lines":[" // SendWALMessage from sending on a closed channel (which panics in Go)."," var walShuttingDown atomic.Bool"," ","+// walCheckpointActive is set during binary checkpoint writes.","+// While active, SendWALMessage skips sending (returns true) because the","+// snapshot captures all in-memory data, making WAL writes redundant.","+var walCheckpointActive atomic.Bool","+"," // WALMessage represents a single metric write to be appended to the WAL."," // Cluster and Node are NOT stored in the WAL record (inferred from file path)."," type WALMessage struct {"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"cd5c0e09-d58b-4a57-b2bc-9e0aaca2b2a7","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"61f3167b-1fca-43ae-987d-1a1932920216","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01KBtJQUkuWTrHTBP74qPSDS","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01S7FN4YyTRuFVDfbqDVB2sS","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","old_string":"func SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}","new_string":"func SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tif walCheckpointActive.Load() {\n\t\treturn true // Data safe in memory; snapshot will capture it\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":373,"cache_read_input_tokens":52472,"output_tokens":338,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":373,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7XDbyfrvjEDbsf38vp","type":"assistant","uuid":"bbbb3976-fa0b-459c-a49e-3b3f95eb3b63","timestamp":"2026-03-29T09:12:05.978Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"bbbb3976-fa0b-459c-a49e-3b3f95eb3b63","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01S7FN4YyTRuFVDfbqDVB2sS","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"994d71cb-1eeb-43dc-9380-b1e3683a6400","timestamp":"2026-03-29T09:12:06.002Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"func SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}","newString":"func SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tif walCheckpointActive.Load() {\n\t\treturn true // Data safe in memory; snapshot will capture it\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}","originalFile":"// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.\n// All rights reserved. This file is part of cc-backend.\n// Use of this source code is governed by a MIT-style\n// license that can be found in the LICENSE file.\n\n// Package metricstore provides walCheckpoint.go: WAL-based checkpoint implementation.\n//\n// This replaces the Avro shadow tree with an append-only Write-Ahead Log (WAL)\n// per host, eliminating the extra memory overhead of the AvroStore and providing\n// truly continuous (per-write) crash safety.\n//\n// # Architecture\n//\n//\tMetric write (DecodeLine)\n//\t │\n//\t ├─► WriteToLevel() → main MemoryStore (unchanged)\n//\t │\n//\t └─► WALMessages channel\n//\t │\n//\t ▼\n//\t WALStaging goroutine\n//\t │\n//\t ▼\n//\t checkpoints/cluster/host/current.wal (append-only, binary)\n//\n//\tPeriodic checkpoint (Checkpointing goroutine):\n//\t 1. Write .bin snapshot (column-oriented, from main tree)\n//\t 2. Signal WALStaging to truncate current.wal per host\n//\n//\tOn restart (FromCheckpoint):\n//\t 1. Load most recent .bin snapshot\n//\t 2. Replay current.wal (overwrite-safe: buffer.write handles duplicate timestamps)\n//\n// # WAL Record Format\n//\n//\t[4B magic 0xCC1DA7A1][4B payload_len][payload][4B CRC32]\n//\n//\tpayload:\n//\t [8B timestamp int64]\n//\t [2B metric_name_len uint16][N metric name bytes]\n//\t [1B selector_count uint8]\n//\t per selector: [1B selector_len uint8][M selector bytes]\n//\t [4B value float32 bits]\n//\n// # Binary Snapshot Format\n//\n//\t[4B magic 0xCC5B0001][8B from int64][8B to int64]\n//\tLevel tree (recursive):\n//\t [4B num_metrics uint32]\n//\t per metric:\n//\t [2B name_len uint16][N name bytes]\n//\t [8B frequency int64][8B start int64]\n//\t [4B num_values uint32][num_values × 4B float32]\n//\t [4B num_children uint32]\n//\t per child: [2B name_len uint16][N name bytes] + Level (recursive)\npackage metricstore\n\nimport (\n\t\"bufio\"\n\t\"context\"\n\t\"encoding/binary\"\n\t\"fmt\"\n\t\"hash/crc32\"\n\t\"hash/fnv\"\n\t\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\n\t\"time\"\n\n\tcclog \"github.com/ClusterCockpit/cc-lib/v2/ccLogger\"\n\t\"github.com/ClusterCockpit/cc-lib/v2/schema\"\n)\n\n// Magic numbers for binary formats.\nconst (\n\twalFileMagic = uint32(0xCC1DA701) // WAL file header magic\n\twalRecordMagic = uint32(0xCC1DA7A1) // WAL record magic\n\tsnapFileMagic = uint32(0xCC5B0001) // Binary snapshot magic\n)\n\n// walShardChs holds per-shard channels for WAL messages.\n// Initialized by WALStaging; nil when WAL is not active.\nvar walShardChs []chan *WALMessage\n\n// walShardRotateChs holds per-shard channels for WAL rotation requests.\nvar walShardRotateChs []chan walRotateReq\n\n// walNumShards stores the number of shards (set during WALStaging init).\nvar walNumShards int\n\n// walStagingWg tracks WALStaging goroutine exits for shutdown synchronization.\nvar walStagingWg sync.WaitGroup\n\n// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool\n\n// walCheckpointActive is set during binary checkpoint writes.\n// While active, SendWALMessage skips sending (returns true) because the\n// snapshot captures all in-memory data, making WAL writes redundant.\nvar walCheckpointActive atomic.Bool\n\n// WALMessage represents a single metric write to be appended to the WAL.\n// Cluster and Node are NOT stored in the WAL record (inferred from file path).\ntype WALMessage struct {\n\tMetricName string\n\tCluster string\n\tNode string\n\tSelector []string\n\tValue schema.Float\n\tTimestamp int64\n}\n\n// walRotateReq requests WAL file rotation for a specific host directory.\n// The done channel is closed by the WAL goroutine when rotation is complete.\ntype walRotateReq struct {\n\thostDir string\n\tdone chan struct{}\n}\n\n// walFileState holds an open WAL file handle and buffered writer for one host directory.\ntype walFileState struct {\n\tf *os.File\n\tw *bufio.Writer\n\tdirty bool\n\tsize int64 // approximate bytes written (tracked from open + writes)\n}\n\n// walFlushInterval controls how often dirty WAL files are flushed to disk.\n// Decoupling flushes from message processing lets the consumer run at memory\n// speed, amortizing syscall overhead across many writes.\nconst walFlushInterval = 1 * time.Second\n\n// walShardIndex computes which shard a message belongs to based on cluster+node.\n// Uses FNV-1a hash for fast, well-distributed mapping.\nfunc walShardIndex(cluster, node string) int {\n\th := fnv.New32a()\n\th.Write([]byte(cluster))\n\th.Write([]byte{0})\n\th.Write([]byte(node))\n\treturn int(h.Sum32()) % walNumShards\n}\n\n// SendWALMessage routes a WAL message to the appropriate shard channel.\n// Returns false if the channel is full or shutdown is in progress.\nfunc SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}\n\n// WALStaging starts N sharded background goroutines that receive WALMessage items\n// and append binary WAL records to per-host current.wal files.\n// Each shard owns a subset of hosts (determined by hash of cluster+node),\n// parallelizing serialization and I/O while keeping per-host writes serial.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\treturn\n\t}\n\n\twalNumShards = max(Keys.NumWorkers, 1)\n\tchBufSize := max(65536/walNumShards, 1024)\n\n\twalShardChs = make([]chan *WALMessage, walNumShards)\n\twalShardRotateChs = make([]chan walRotateReq, walNumShards)\n\n\tfor i := range walNumShards {\n\t\twalShardChs[i] = make(chan *WALMessage, chBufSize)\n\t\twalShardRotateChs[i] = make(chan walRotateReq, 64)\n\t}\n\n\tfor i := range walNumShards {\n\t\tmsgCh := walShardChs[i]\n\t\trotateCh := walShardRotateChs[i]\n\n\t\twalStagingWg.Add(1)\n\t\twg.Go(func() {\n\t\t\tdefer walStagingWg.Done()\n\t\t\thostFiles := make(map[string]*walFileState)\n\n\t\t\tdefer func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.f != nil {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.f.Close()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}()\n\n\t\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\t\tws, ok := hostFiles[hostDir]\n\t\t\t\tif ok {\n\t\t\t\t\treturn ws\n\t\t\t\t}\n\n\t\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t\t// Write file header magic if file is new (empty).\n\t\t\t\tinfo, err := f.Stat()\n\t\t\t\tvar fileSize int64\n\t\t\t\tif err == nil {\n\t\t\t\t\tfileSize = info.Size()\n\t\t\t\t}\n\t\t\t\tif err == nil && fileSize == 0 {\n\t\t\t\t\tvar hdr [4]byte\n\t\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\t\tf.Close()\n\t\t\t\t\t\treturn nil\n\t\t\t\t\t}\n\t\t\t\t\tfileSize = 4\n\t\t\t\t}\n\n\t\t\t\tws = &walFileState{f: f, w: w, size: fileSize}\n\t\t\t\thostFiles[hostDir] = ws\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\t\tif ws == nil {\n\t\t\t\t\treturn\n\t\t\t\t}\n\n\t\t\t\t// Enforce max WAL size: force-rotate before writing if limit is exceeded.\n\t\t\t\t// The in-memory store still holds the data; only crash-recovery coverage is lost.\n\t\t\t\tif maxSize := Keys.Checkpoints.MaxWALSize; maxSize > 0 && ws.size >= maxSize {\n\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL: force-rotating %s (size %d >= limit %d)\",\n\t\t\t\t\t\thostDir, ws.size, maxSize)\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, hostDir)\n\t\t\t\t\tws = getOrOpenWAL(hostDir)\n\t\t\t\t\tif ws == nil {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t}\n\n\t\t\t\tn, err := writeWALRecordDirect(ws.w, msg)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t\t}\n\t\t\t\tws.size += int64(n)\n\t\t\t\tws.dirty = true\n\t\t\t}\n\n\t\t\tprocessRotate := func(req walRotateReq) {\n\t\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\t\tif ok && ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t\t}\n\t\t\t\tclose(req.done)\n\t\t\t}\n\n\t\t\tflushDirty := func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.dirty {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.dirty = false\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tticker := time.NewTicker(walFlushInterval)\n\t\t\tdefer ticker.Stop()\n\n\t\t\t// drainBatch processes up to 4096 pending messages without blocking.\n\t\t\t// Returns false if the channel was closed.\n\t\t\tdrainBatch := func() bool {\n\t\t\t\tfor range 4096 {\n\t\t\t\t\tselect {\n\t\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\t\tif !ok {\n\t\t\t\t\t\t\tflushDirty()\n\t\t\t\t\t\t\treturn false\n\t\t\t\t\t\t}\n\t\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\t\tprocessRotate(req)\n\t\t\t\t\tdefault:\n\t\t\t\t\t\treturn true\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\treturn true\n\t\t\t}\n\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase <-ctx.Done():\n\t\t\t\t\t// On shutdown, skip draining buffered messages — a full binary\n\t\t\t\t\t// checkpoint will be written from in-memory state, making\n\t\t\t\t\t// buffered WAL records redundant.\n\t\t\t\t\tflushDirty()\n\t\t\t\t\treturn\n\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\tif !ok {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tif !drainBatch() {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\t// No flush here — timer handles periodic flushing.\n\t\t\t\tcase <-ticker.C:\n\t\t\t\t\tflushDirty()\n\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\t}\n\t\t\t}\n\t\t})\n\t}\n}\n\n// WaitForWALStagingDrain blocks until all WALStaging goroutines have exited.\n// Must be called after closing walShardChs to ensure all file handles are\n// flushed and closed before checkpoint writes begin.\nfunc WaitForWALStagingDrain() {\n\twalStagingWg.Wait()\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete. Each request is routed to the\n// shard that owns the host directory.\n//\n// If shutdown is in progress (WAL staging goroutines may have exited),\n// rotation is skipped to avoid deadlocking on abandoned channels.\nfunc RotateWALFiles(hostDirs []string) {\n\tif walShardRotateChs == nil || walShuttingDown.Load() {\n\t\treturn\n\t}\n\tdeadline := time.After(2 * time.Minute)\n\tdones := make([]chan struct{}, 0, len(hostDirs))\n\tfor _, dir := range hostDirs {\n\t\tdone := make(chan struct{})\n\t\tshard := walShardIndexFromDir(dir)\n\t\tselect {\n\t\tcase walShardRotateChs[shard] <- walRotateReq{hostDir: dir, done: done}:\n\t\t\tdones = append(dones, done)\n\t\tcase <-deadline:\n\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL rotation send timed out, %d of %d hosts remaining\",\n\t\t\t\tlen(hostDirs)-len(dones), len(hostDirs))\n\t\t\tgoto waitDones\n\t\t}\n\t}\nwaitDones:\n\tfor _, done := range dones {\n\t\tselect {\n\t\tcase <-done:\n\t\tcase <-time.After(30 * time.Second):\n\t\t\tcclog.Warn(\"[METRICSTORE]> WAL rotation completion timed out, continuing\")\n\t\t\treturn\n\t\t}\n\t}\n}\n\n// walShardIndexFromDir extracts cluster and node from a host directory path\n// and returns the shard index. The path format is: rootDir/cluster/node\nfunc walShardIndexFromDir(hostDir string) int {\n\t// hostDir = .../cluster/node — extract last two path components\n\tnode := path.Base(hostDir)\n\tcluster := path.Base(path.Dir(hostDir))\n\treturn walShardIndex(cluster, node)\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFilesAfterShutdown(hostDirs []string) {\n\tfor _, dir := range hostDirs {\n\t\twalPath := path.Join(dir, \"current.wal\")\n\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t}\n\t}\n}\n\n// writeWALRecordDirect encodes a WAL record into a contiguous buffer first,\n// then writes it to the bufio.Writer in a single call. This prevents partial\n// records in the write buffer if a write error occurs mid-record (e.g. disk full).\n// Returns the number of bytes written and any error.\nfunc writeWALRecordDirect(w *bufio.Writer, msg *WALMessage) (int, error) {\n\t// Compute payload and total record size.\n\tpayloadSize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tpayloadSize += 1 + len(s)\n\t}\n\t// Total: 8 (header) + payload + 4 (CRC).\n\ttotalSize := 8 + payloadSize + 4\n\n\t// Use stack buffer for typical small records, heap-allocate only for large ones.\n\tvar stackBuf [256]byte\n\tvar buf []byte\n\tif totalSize <= len(stackBuf) {\n\t\tbuf = stackBuf[:totalSize]\n\t} else {\n\t\tbuf = make([]byte, totalSize)\n\t}\n\n\t// Header: magic + payload length.\n\tbinary.LittleEndian.PutUint32(buf[0:4], walRecordMagic)\n\tbinary.LittleEndian.PutUint32(buf[4:8], uint32(payloadSize))\n\n\t// Payload starts at offset 8.\n\tp := 8\n\n\t// Timestamp (8 bytes).\n\tbinary.LittleEndian.PutUint64(buf[p:p+8], uint64(msg.Timestamp))\n\tp += 8\n\n\t// Metric name length (2 bytes) + metric name.\n\tbinary.LittleEndian.PutUint16(buf[p:p+2], uint16(len(msg.MetricName)))\n\tp += 2\n\tp += copy(buf[p:], msg.MetricName)\n\n\t// Selector count (1 byte).\n\tbuf[p] = byte(len(msg.Selector))\n\tp++\n\n\t// Selectors (1-byte length + bytes each).\n\tfor _, sel := range msg.Selector {\n\t\tbuf[p] = byte(len(sel))\n\t\tp++\n\t\tp += copy(buf[p:], sel)\n\t}\n\n\t// Value (4 bytes, float32 bits).\n\tbinary.LittleEndian.PutUint32(buf[p:p+4], math.Float32bits(float32(msg.Value)))\n\tp += 4\n\n\t// CRC32 over payload (bytes 8..8+payloadSize).\n\tcrc := crc32.ChecksumIEEE(buf[8 : 8+payloadSize])\n\tbinary.LittleEndian.PutUint32(buf[p:p+4], crc)\n\n\t// Single atomic write to the buffered writer.\n\tn, err := w.Write(buf)\n\treturn n, err\n}\n\n// readWALRecord reads one WAL record from the reader.\n// Returns (nil, nil) on clean EOF. Returns error on data corruption.\n// A CRC mismatch indicates a truncated trailing record (expected on crash).\nfunc readWALRecord(r io.Reader) (*WALMessage, error) {\n\tvar magic uint32\n\tif err := binary.Read(r, binary.LittleEndian, &magic); err != nil {\n\t\tif err == io.EOF {\n\t\t\treturn nil, nil // Clean EOF\n\t\t}\n\t\treturn nil, fmt.Errorf(\"read record magic: %w\", err)\n\t}\n\n\tif magic != walRecordMagic {\n\t\treturn nil, fmt.Errorf(\"invalid record magic 0x%08X (expected 0x%08X)\", magic, walRecordMagic)\n\t}\n\n\tvar payloadLen uint32\n\tif err := binary.Read(r, binary.LittleEndian, &payloadLen); err != nil {\n\t\treturn nil, fmt.Errorf(\"read payload length: %w\", err)\n\t}\n\n\tif payloadLen > 1<<20 { // 1 MB sanity limit\n\t\treturn nil, fmt.Errorf(\"record payload too large: %d bytes\", payloadLen)\n\t}\n\n\tpayload := make([]byte, payloadLen)\n\tif _, err := io.ReadFull(r, payload); err != nil {\n\t\treturn nil, fmt.Errorf(\"read payload: %w\", err)\n\t}\n\n\tvar storedCRC uint32\n\tif err := binary.Read(r, binary.LittleEndian, &storedCRC); err != nil {\n\t\treturn nil, fmt.Errorf(\"read CRC: %w\", err)\n\t}\n\n\tif crc32.ChecksumIEEE(payload) != storedCRC {\n\t\treturn nil, fmt.Errorf(\"CRC mismatch (truncated write or corruption)\")\n\t}\n\n\treturn parseWALPayload(payload)\n}\n\n// parseWALPayload decodes a binary payload into a WALMessage.\nfunc parseWALPayload(payload []byte) (*WALMessage, error) {\n\tif len(payload) < 8+2+1+4 {\n\t\treturn nil, fmt.Errorf(\"payload too short: %d bytes\", len(payload))\n\t}\n\n\toffset := 0\n\n\t// Timestamp (8 bytes)\n\tts := int64(binary.LittleEndian.Uint64(payload[offset : offset+8]))\n\toffset += 8\n\n\t// Metric name (2-byte length + bytes)\n\tif offset+2 > len(payload) {\n\t\treturn nil, fmt.Errorf(\"metric name length overflows payload\")\n\t}\n\tmLen := int(binary.LittleEndian.Uint16(payload[offset : offset+2]))\n\toffset += 2\n\n\tif offset+mLen > len(payload) {\n\t\treturn nil, fmt.Errorf(\"metric name overflows payload\")\n\t}\n\tmetricName := string(payload[offset : offset+mLen])\n\toffset += mLen\n\n\t// Selector count (1 byte)\n\tif offset >= len(payload) {\n\t\treturn nil, fmt.Errorf(\"selector count overflows payload\")\n\t}\n\tselCount := int(payload[offset])\n\toffset++\n\n\tselectors := make([]string, selCount)\n\tfor i := range selCount {\n\t\tif offset >= len(payload) {\n\t\t\treturn nil, fmt.Errorf(\"selector[%d] length overflows payload\", i)\n\t\t}\n\t\tsLen := int(payload[offset])\n\t\toffset++\n\n\t\tif offset+sLen > len(payload) {\n\t\t\treturn nil, fmt.Errorf(\"selector[%d] data overflows payload\", i)\n\t\t}\n\t\tselectors[i] = string(payload[offset : offset+sLen])\n\t\toffset += sLen\n\t}\n\n\t// Value (4 bytes, float32 bits)\n\tif offset+4 > len(payload) {\n\t\treturn nil, fmt.Errorf(\"value overflows payload\")\n\t}\n\tbits := binary.LittleEndian.Uint32(payload[offset : offset+4])\n\tvalue := schema.Float(math.Float32frombits(bits))\n\n\treturn &WALMessage{\n\t\tMetricName: metricName,\n\t\tTimestamp: ts,\n\t\tSelector: selectors,\n\t\tValue: value,\n\t}, nil\n}\n\n// loadWALFile reads a WAL file and replays all valid records into the Level tree.\n// l is the host-level node. Corrupt or partial trailing records are silently skipped\n// (expected on crash). Records older than 'from' are skipped.\nfunc (l *Level) loadWALFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\n\t// Verify file header magic.\n\tvar fileMagic uint32\n\tif err := binary.Read(br, binary.LittleEndian, &fileMagic); err != nil {\n\t\tif err == io.EOF {\n\t\t\treturn nil // Empty file, no data\n\t\t}\n\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: read file header: %w\", err)\n\t}\n\n\tif fileMagic != walFileMagic {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: invalid file magic 0x%08X (expected 0x%08X)\", fileMagic, walFileMagic)\n\t}\n\n\t// Cache level lookups to avoid repeated tree traversal.\n\tlvlCache := make(map[string]*Level)\n\n\tfor {\n\t\tmsg, err := readWALRecord(br)\n\t\tif err != nil {\n\t\t\t// Truncated trailing record is expected after a crash; stop replaying.\n\t\t\tcclog.Debugf(\"[METRICSTORE]> WAL: stopping replay at corrupted/partial record: %v\", err)\n\t\t\tbreak\n\t\t}\n\t\tif msg == nil {\n\t\t\tbreak // Clean EOF\n\t\t}\n\n\t\tif msg.Timestamp < from {\n\t\t\tcontinue // Older than retention window\n\t\t}\n\n\t\tminfo, ok := m.Metrics[msg.MetricName]\n\t\tif !ok {\n\t\t\tcontinue // Unknown metric (config may have changed)\n\t\t}\n\n\t\t// Cache key is the null-separated selector path.\n\t\tcacheKey := joinSelector(msg.Selector)\n\t\tlvl, ok := lvlCache[cacheKey]\n\t\tif !ok {\n\t\t\tlvl = l.findLevelOrCreate(msg.Selector, len(m.Metrics))\n\t\t\tlvlCache[cacheKey] = lvl\n\t\t}\n\n\t\t// Write directly to the buffer, same as WriteToLevel but without the\n\t\t// global level lookup (we already have the right level).\n\t\tlvl.lock.Lock()\n\t\tb := lvl.metrics[minfo.offset]\n\t\tif b == nil {\n\t\t\tb = newBuffer(msg.Timestamp, minfo.Frequency)\n\t\t\tlvl.metrics[minfo.offset] = b\n\t\t}\n\t\tnb, writeErr := b.write(msg.Timestamp, msg.Value)\n\t\tif writeErr == nil && b != nb {\n\t\t\tlvl.metrics[minfo.offset] = nb\n\t\t}\n\t\t// Ignore write errors for timestamps before buffer start (can happen when\n\t\t// replaying WAL entries that predate a loaded snapshot's start time).\n\t\tlvl.lock.Unlock()\n\t}\n\n\treturn nil\n}\n\n// joinSelector builds a cache key from a selector slice using null bytes as separators.\nfunc joinSelector(sel []string) string {\n\tif len(sel) == 0 {\n\t\treturn \"\"\n\t}\n\tvar result strings.Builder\n\tresult.WriteString(sel[0])\n\tfor i := 1; i < len(sel); i++ {\n\t\tresult.WriteString(\"\\x00\" + sel[i])\n\t}\n\treturn result.String()\n}\n\n// ToCheckpointWAL writes binary snapshot files for all hosts in parallel.\n// Returns the number of files written, the list of host directories that were\n// successfully checkpointed (for WAL rotation), and any errors.\nfunc (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string, error) {\n\t// Collect all cluster/host pairs.\n\tm.root.lock.RLock()\n\ttotalHosts := 0\n\tfor _, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\ttotalHosts += len(l1.children)\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\tlevels := make([]*Level, 0, totalHosts)\n\tselectors := make([][]string, 0, totalHosts)\n\n\tm.root.lock.RLock()\n\tfor sel1, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\tfor sel2, l2 := range l1.children {\n\t\t\tlevels = append(levels, l2)\n\t\t\tselectors = append(selectors, []string{sel1, sel2})\n\t\t}\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\ttype workItem struct {\n\t\tlevel *Level\n\t\thostDir string\n\t\tselector []string\n\t}\n\n\ttotalWork := len(levels)\n\tcclog.Infof(\"[METRICSTORE]> Starting binary checkpoint for %d hosts with %d workers\", totalWork, Keys.NumWorkers)\n\n\tn, errs, completed := int32(0), int32(0), int32(0)\n\tvar successDirs []string\n\tvar successMu sync.Mutex\n\n\tvar wg sync.WaitGroup\n\twg.Add(Keys.NumWorkers)\n\twork := make(chan workItem, Keys.NumWorkers*2)\n\n\t// Progress logging goroutine.\n\tstopProgress := make(chan struct{})\n\tgo func() {\n\t\tticker := time.NewTicker(10 * time.Second)\n\t\tdefer ticker.Stop()\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ticker.C:\n\t\t\t\tcclog.Infof(\"[METRICSTORE]> Checkpoint progress: %d/%d hosts (%d written, %d errors)\",\n\t\t\t\t\tatomic.LoadInt32(&completed), totalWork, atomic.LoadInt32(&n), atomic.LoadInt32(&errs))\n\t\t\tcase <-stopProgress:\n\t\t\t\treturn\n\t\t\t}\n\t\t}\n\t}()\n\n\tfor range Keys.NumWorkers {\n\t\tgo func() {\n\t\t\tdefer wg.Done()\n\t\t\tfor wi := range work {\n\t\t\t\terr := wi.level.toCheckpointBinary(wi.hostDir, from, to, m)\n\t\t\t\tif err != nil {\n\t\t\t\t\tif err == ErrNoNewArchiveData {\n\t\t\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t\t\t\tcontinue\n\t\t\t\t\t}\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpoint error for %s: %v\", wi.hostDir, err)\n\t\t\t\t\tatomic.AddInt32(&errs, 1)\n\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tsuccessMu.Lock()\n\t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n\t\t\t\t\tsuccessMu.Unlock()\n\t\t\t\t}\n\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t}\n\t\t}()\n\t}\n\n\tfor i := range levels {\n\t\thostDir := path.Join(dir, path.Join(selectors[i]...))\n\t\twork <- workItem{\n\t\t\tlevel: levels[i],\n\t\t\thostDir: hostDir,\n\t\t\tselector: selectors[i],\n\t\t}\n\t}\n\tclose(work)\n\twg.Wait()\n\tclose(stopProgress)\n\n\tif errs > 0 {\n\t\treturn int(n), successDirs, fmt.Errorf(\"[METRICSTORE]> %d errors during binary checkpoint (%d successes)\", errs, n)\n\t}\n\treturn int(n), successDirs, nil\n}\n\n// toCheckpointBinary writes a binary snapshot file for a single host-level node.\n// Uses atomic rename (write to .tmp then rename) to avoid partial reads on crash.\nfunc (l *Level) toCheckpointBinary(dir string, from, to int64, m *MemoryStore) error {\n\tcf, err := l.toCheckpointFile(from, to, m)\n\tif err != nil {\n\t\treturn err\n\t}\n\tif cf == nil {\n\t\treturn ErrNoNewArchiveData\n\t}\n\n\tif err := os.MkdirAll(dir, CheckpointDirPerms); err != nil {\n\t\treturn fmt.Errorf(\"mkdir %s: %w\", dir, err)\n\t}\n\n\t// Write to a temp file first, then rename (atomic on POSIX).\n\ttmpPath := path.Join(dir, fmt.Sprintf(\"%d.bin.tmp\", from))\n\tfinalPath := path.Join(dir, fmt.Sprintf(\"%d.bin\", from))\n\n\tf, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"open binary snapshot %s: %w\", tmpPath, err)\n\t}\n\n\tbw := bufio.NewWriter(f)\n\tif err := writeBinarySnapshotFile(bw, cf); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn fmt.Errorf(\"write binary snapshot: %w\", err)\n\t}\n\tif err := bw.Flush(); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn err\n\t}\n\tf.Close()\n\n\treturn os.Rename(tmpPath, finalPath)\n}\n\n// writeBinarySnapshotFile writes the binary snapshot file header and level tree.\nfunc writeBinarySnapshotFile(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, snapFileMagic); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.From); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.To); err != nil {\n\t\treturn err\n\t}\n\treturn writeBinaryLevel(w, cf)\n}\n\n// writeBinaryLevel recursively writes a CheckpointFile level in binary format.\nfunc writeBinaryLevel(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Metrics))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, metric := range cf.Metrics {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Frequency); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Start); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(metric.Data))); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tfor _, v := range metric.Data {\n\t\t\tif err := binary.Write(w, binary.LittleEndian, math.Float32bits(float32(v))); err != nil {\n\t\t\t\treturn err\n\t\t\t}\n\t\t}\n\t}\n\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Children))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, child := range cf.Children {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := writeBinaryLevel(w, child); err != nil {\n\t\t\treturn err\n\t\t}\n\t}\n\n\treturn nil\n}\n\n// writeString16 writes a 2-byte length-prefixed string to w.\nfunc writeString16(w io.Writer, s string) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint16(len(s))); err != nil {\n\t\treturn err\n\t}\n\t_, err := io.WriteString(w, s)\n\treturn err\n}\n\n// loadBinaryFile reads a binary snapshot file and loads data into the Level tree.\n// The retention check (from) is applied to the file's 'to' timestamp.\nfunc (l *Level) loadBinaryFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\n\tvar magic uint32\n\tif err := binary.Read(br, binary.LittleEndian, &magic); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read magic: %w\", err)\n\t}\n\tif magic != snapFileMagic {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: invalid magic 0x%08X (expected 0x%08X)\", magic, snapFileMagic)\n\t}\n\n\tvar fileFrom, fileTo int64\n\tif err := binary.Read(br, binary.LittleEndian, &fileFrom); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read from: %w\", err)\n\t}\n\tif err := binary.Read(br, binary.LittleEndian, &fileTo); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read to: %w\", err)\n\t}\n\n\tif fileTo != 0 && fileTo < from {\n\t\treturn nil // File is older than retention window, skip it\n\t}\n\n\tcf, err := readBinaryLevel(br)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read level tree: %w\", err)\n\t}\n\tcf.From = fileFrom\n\tcf.To = fileTo\n\n\treturn l.loadFile(cf, m)\n}\n\n// readBinaryLevel recursively reads a level from the binary snapshot format.\nfunc readBinaryLevel(r io.Reader) (*CheckpointFile, error) {\n\tcf := &CheckpointFile{\n\t\tMetrics: make(map[string]*CheckpointMetrics),\n\t\tChildren: make(map[string]*CheckpointFile),\n\t}\n\n\tvar numMetrics uint32\n\tif err := binary.Read(r, binary.LittleEndian, &numMetrics); err != nil {\n\t\treturn nil, fmt.Errorf(\"read num_metrics: %w\", err)\n\t}\n\n\tfor range numMetrics {\n\t\tname, err := readString16(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read metric name: %w\", err)\n\t\t}\n\n\t\tvar freq, start int64\n\t\tif err := binary.Read(r, binary.LittleEndian, &freq); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read frequency for %s: %w\", name, err)\n\t\t}\n\t\tif err := binary.Read(r, binary.LittleEndian, &start); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read start for %s: %w\", name, err)\n\t\t}\n\n\t\tvar numValues uint32\n\t\tif err := binary.Read(r, binary.LittleEndian, &numValues); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read num_values for %s: %w\", name, err)\n\t\t}\n\n\t\tdata := make([]schema.Float, numValues)\n\t\tfor i := range numValues {\n\t\t\tvar bits uint32\n\t\t\tif err := binary.Read(r, binary.LittleEndian, &bits); err != nil {\n\t\t\t\treturn nil, fmt.Errorf(\"read value[%d] for %s: %w\", i, name, err)\n\t\t\t}\n\t\t\tdata[i] = schema.Float(math.Float32frombits(bits))\n\t\t}\n\n\t\tcf.Metrics[name] = &CheckpointMetrics{\n\t\t\tFrequency: freq,\n\t\t\tStart: start,\n\t\t\tData: data,\n\t\t}\n\t}\n\n\tvar numChildren uint32\n\tif err := binary.Read(r, binary.LittleEndian, &numChildren); err != nil {\n\t\treturn nil, fmt.Errorf(\"read num_children: %w\", err)\n\t}\n\n\tfor range numChildren {\n\t\tchildName, err := readString16(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read child name: %w\", err)\n\t\t}\n\n\t\tchild, err := readBinaryLevel(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read child %s: %w\", childName, err)\n\t\t}\n\t\tcf.Children[childName] = child\n\t}\n\n\treturn cf, nil\n}\n\n// readString16 reads a 2-byte length-prefixed string from r.\nfunc readString16(r io.Reader) (string, error) {\n\tvar sLen uint16\n\tif err := binary.Read(r, binary.LittleEndian, &sLen); err != nil {\n\t\treturn \"\", err\n\t}\n\tbuf := make([]byte, sLen)\n\tif _, err := io.ReadFull(r, buf); err != nil {\n\t\treturn \"\", err\n\t}\n\treturn string(buf), nil\n}\n","structuredPatch":[{"oldStart":151,"oldLines":6,"newStart":151,"newLines":9,"lines":[" if walShardChs == nil || walShuttingDown.Load() {"," return false"," }","+ if walCheckpointActive.Load() {","+ return true // Data safe in memory; snapshot will capture it","+ }"," shard := walShardIndex(msg.Cluster, msg.Node)"," select {"," case walShardChs[shard] <- msg:"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"bbbb3976-fa0b-459c-a49e-3b3f95eb3b63","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"994d71cb-1eeb-43dc-9380-b1e3683a6400","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01RvuBn1go7mQJA1gJRofSQR","type":"message","role":"assistant","content":[{"type":"text","text":"**Step 2: Remove direct WAL deletion race** in `ToCheckpointWAL`:"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":475,"cache_read_input_tokens":52845,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":475},"output_tokens":1,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7XgBtTi2u9s9KAT8mF","type":"assistant","uuid":"d31ed0f7-e8c5-4616-bf9e-54058579e9bb","timestamp":"2026-03-29T09:12:09.104Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"d31ed0f7-e8c5-4616-bf9e-54058579e9bb","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01RvuBn1go7mQJA1gJRofSQR","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_013pjCPn2AvZdrG31MK5newo","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","old_string":"\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tsuccessMu.Lock()","new_string":"\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\tsuccessMu.Lock()"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":475,"cache_read_input_tokens":52845,"output_tokens":299,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":475,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7XgBtTi2u9s9KAT8mF","type":"assistant","uuid":"4a04d73e-3bda-470e-a534-b37af80f7c77","timestamp":"2026-03-29T09:12:12.040Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"4a04d73e-3bda-470e-a534-b37af80f7c77","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_013pjCPn2AvZdrG31MK5newo","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"029e1b61-4f3a-48d4-a30a-7d98e00c7cca","timestamp":"2026-03-29T09:12:12.065Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tsuccessMu.Lock()","newString":"\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\tsuccessMu.Lock()","originalFile":"// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.\n// All rights reserved. This file is part of cc-backend.\n// Use of this source code is governed by a MIT-style\n// license that can be found in the LICENSE file.\n\n// Package metricstore provides walCheckpoint.go: WAL-based checkpoint implementation.\n//\n// This replaces the Avro shadow tree with an append-only Write-Ahead Log (WAL)\n// per host, eliminating the extra memory overhead of the AvroStore and providing\n// truly continuous (per-write) crash safety.\n//\n// # Architecture\n//\n//\tMetric write (DecodeLine)\n//\t │\n//\t ├─► WriteToLevel() → main MemoryStore (unchanged)\n//\t │\n//\t └─► WALMessages channel\n//\t │\n//\t ▼\n//\t WALStaging goroutine\n//\t │\n//\t ▼\n//\t checkpoints/cluster/host/current.wal (append-only, binary)\n//\n//\tPeriodic checkpoint (Checkpointing goroutine):\n//\t 1. Write .bin snapshot (column-oriented, from main tree)\n//\t 2. Signal WALStaging to truncate current.wal per host\n//\n//\tOn restart (FromCheckpoint):\n//\t 1. Load most recent .bin snapshot\n//\t 2. Replay current.wal (overwrite-safe: buffer.write handles duplicate timestamps)\n//\n// # WAL Record Format\n//\n//\t[4B magic 0xCC1DA7A1][4B payload_len][payload][4B CRC32]\n//\n//\tpayload:\n//\t [8B timestamp int64]\n//\t [2B metric_name_len uint16][N metric name bytes]\n//\t [1B selector_count uint8]\n//\t per selector: [1B selector_len uint8][M selector bytes]\n//\t [4B value float32 bits]\n//\n// # Binary Snapshot Format\n//\n//\t[4B magic 0xCC5B0001][8B from int64][8B to int64]\n//\tLevel tree (recursive):\n//\t [4B num_metrics uint32]\n//\t per metric:\n//\t [2B name_len uint16][N name bytes]\n//\t [8B frequency int64][8B start int64]\n//\t [4B num_values uint32][num_values × 4B float32]\n//\t [4B num_children uint32]\n//\t per child: [2B name_len uint16][N name bytes] + Level (recursive)\npackage metricstore\n\nimport (\n\t\"bufio\"\n\t\"context\"\n\t\"encoding/binary\"\n\t\"fmt\"\n\t\"hash/crc32\"\n\t\"hash/fnv\"\n\t\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\n\t\"time\"\n\n\tcclog \"github.com/ClusterCockpit/cc-lib/v2/ccLogger\"\n\t\"github.com/ClusterCockpit/cc-lib/v2/schema\"\n)\n\n// Magic numbers for binary formats.\nconst (\n\twalFileMagic = uint32(0xCC1DA701) // WAL file header magic\n\twalRecordMagic = uint32(0xCC1DA7A1) // WAL record magic\n\tsnapFileMagic = uint32(0xCC5B0001) // Binary snapshot magic\n)\n\n// walShardChs holds per-shard channels for WAL messages.\n// Initialized by WALStaging; nil when WAL is not active.\nvar walShardChs []chan *WALMessage\n\n// walShardRotateChs holds per-shard channels for WAL rotation requests.\nvar walShardRotateChs []chan walRotateReq\n\n// walNumShards stores the number of shards (set during WALStaging init).\nvar walNumShards int\n\n// walStagingWg tracks WALStaging goroutine exits for shutdown synchronization.\nvar walStagingWg sync.WaitGroup\n\n// walShuttingDown is set before closing shard channels to prevent\n// SendWALMessage from sending on a closed channel (which panics in Go).\nvar walShuttingDown atomic.Bool\n\n// walCheckpointActive is set during binary checkpoint writes.\n// While active, SendWALMessage skips sending (returns true) because the\n// snapshot captures all in-memory data, making WAL writes redundant.\nvar walCheckpointActive atomic.Bool\n\n// WALMessage represents a single metric write to be appended to the WAL.\n// Cluster and Node are NOT stored in the WAL record (inferred from file path).\ntype WALMessage struct {\n\tMetricName string\n\tCluster string\n\tNode string\n\tSelector []string\n\tValue schema.Float\n\tTimestamp int64\n}\n\n// walRotateReq requests WAL file rotation for a specific host directory.\n// The done channel is closed by the WAL goroutine when rotation is complete.\ntype walRotateReq struct {\n\thostDir string\n\tdone chan struct{}\n}\n\n// walFileState holds an open WAL file handle and buffered writer for one host directory.\ntype walFileState struct {\n\tf *os.File\n\tw *bufio.Writer\n\tdirty bool\n\tsize int64 // approximate bytes written (tracked from open + writes)\n}\n\n// walFlushInterval controls how often dirty WAL files are flushed to disk.\n// Decoupling flushes from message processing lets the consumer run at memory\n// speed, amortizing syscall overhead across many writes.\nconst walFlushInterval = 1 * time.Second\n\n// walShardIndex computes which shard a message belongs to based on cluster+node.\n// Uses FNV-1a hash for fast, well-distributed mapping.\nfunc walShardIndex(cluster, node string) int {\n\th := fnv.New32a()\n\th.Write([]byte(cluster))\n\th.Write([]byte{0})\n\th.Write([]byte(node))\n\treturn int(h.Sum32()) % walNumShards\n}\n\n// SendWALMessage routes a WAL message to the appropriate shard channel.\n// Returns false if the channel is full or shutdown is in progress.\nfunc SendWALMessage(msg *WALMessage) bool {\n\tif walShardChs == nil || walShuttingDown.Load() {\n\t\treturn false\n\t}\n\tif walCheckpointActive.Load() {\n\t\treturn true // Data safe in memory; snapshot will capture it\n\t}\n\tshard := walShardIndex(msg.Cluster, msg.Node)\n\tselect {\n\tcase walShardChs[shard] <- msg:\n\t\treturn true\n\tdefault:\n\t\treturn false\n\t}\n}\n\n// WALStaging starts N sharded background goroutines that receive WALMessage items\n// and append binary WAL records to per-host current.wal files.\n// Each shard owns a subset of hosts (determined by hash of cluster+node),\n// parallelizing serialization and I/O while keeping per-host writes serial.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\treturn\n\t}\n\n\twalNumShards = max(Keys.NumWorkers, 1)\n\tchBufSize := max(65536/walNumShards, 1024)\n\n\twalShardChs = make([]chan *WALMessage, walNumShards)\n\twalShardRotateChs = make([]chan walRotateReq, walNumShards)\n\n\tfor i := range walNumShards {\n\t\twalShardChs[i] = make(chan *WALMessage, chBufSize)\n\t\twalShardRotateChs[i] = make(chan walRotateReq, 64)\n\t}\n\n\tfor i := range walNumShards {\n\t\tmsgCh := walShardChs[i]\n\t\trotateCh := walShardRotateChs[i]\n\n\t\twalStagingWg.Add(1)\n\t\twg.Go(func() {\n\t\t\tdefer walStagingWg.Done()\n\t\t\thostFiles := make(map[string]*walFileState)\n\n\t\t\tdefer func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.f != nil {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.f.Close()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}()\n\n\t\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\t\tws, ok := hostFiles[hostDir]\n\t\t\t\tif ok {\n\t\t\t\t\treturn ws\n\t\t\t\t}\n\n\t\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\n\t\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t\t// Write file header magic if file is new (empty).\n\t\t\t\tinfo, err := f.Stat()\n\t\t\t\tvar fileSize int64\n\t\t\t\tif err == nil {\n\t\t\t\t\tfileSize = info.Size()\n\t\t\t\t}\n\t\t\t\tif err == nil && fileSize == 0 {\n\t\t\t\t\tvar hdr [4]byte\n\t\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\t\tf.Close()\n\t\t\t\t\t\treturn nil\n\t\t\t\t\t}\n\t\t\t\t\tfileSize = 4\n\t\t\t\t}\n\n\t\t\t\tws = &walFileState{f: f, w: w, size: fileSize}\n\t\t\t\thostFiles[hostDir] = ws\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\t\tif ws == nil {\n\t\t\t\t\treturn\n\t\t\t\t}\n\n\t\t\t\t// Enforce max WAL size: force-rotate before writing if limit is exceeded.\n\t\t\t\t// The in-memory store still holds the data; only crash-recovery coverage is lost.\n\t\t\t\tif maxSize := Keys.Checkpoints.MaxWALSize; maxSize > 0 && ws.size >= maxSize {\n\t\t\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL: force-rotating %s (size %d >= limit %d)\",\n\t\t\t\t\t\thostDir, ws.size, maxSize)\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, hostDir)\n\t\t\t\t\tws = getOrOpenWAL(hostDir)\n\t\t\t\t\tif ws == nil {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t}\n\n\t\t\t\tn, err := writeWALRecordDirect(ws.w, msg)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t\t}\n\t\t\t\tws.size += int64(n)\n\t\t\t\tws.dirty = true\n\t\t\t}\n\n\t\t\tprocessRotate := func(req walRotateReq) {\n\t\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\t\tif ok && ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t\t}\n\t\t\t\tclose(req.done)\n\t\t\t}\n\n\t\t\tflushDirty := func() {\n\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\tif ws.dirty {\n\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\tws.dirty = false\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tticker := time.NewTicker(walFlushInterval)\n\t\t\tdefer ticker.Stop()\n\n\t\t\t// drainBatch processes up to 4096 pending messages without blocking.\n\t\t\t// Returns false if the channel was closed.\n\t\t\tdrainBatch := func() bool {\n\t\t\t\tfor range 4096 {\n\t\t\t\t\tselect {\n\t\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\t\tif !ok {\n\t\t\t\t\t\t\tflushDirty()\n\t\t\t\t\t\t\treturn false\n\t\t\t\t\t\t}\n\t\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\t\tprocessRotate(req)\n\t\t\t\t\tdefault:\n\t\t\t\t\t\treturn true\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t\treturn true\n\t\t\t}\n\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase <-ctx.Done():\n\t\t\t\t\t// On shutdown, skip draining buffered messages — a full binary\n\t\t\t\t\t// checkpoint will be written from in-memory state, making\n\t\t\t\t\t// buffered WAL records redundant.\n\t\t\t\t\tflushDirty()\n\t\t\t\t\treturn\n\t\t\t\tcase msg, ok := <-msgCh:\n\t\t\t\t\tif !ok {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\tprocessMsg(msg)\n\t\t\t\t\tif !drainBatch() {\n\t\t\t\t\t\treturn\n\t\t\t\t\t}\n\t\t\t\t\t// No flush here — timer handles periodic flushing.\n\t\t\t\tcase <-ticker.C:\n\t\t\t\t\tflushDirty()\n\t\t\t\tcase req := <-rotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\t}\n\t\t\t}\n\t\t})\n\t}\n}\n\n// WaitForWALStagingDrain blocks until all WALStaging goroutines have exited.\n// Must be called after closing walShardChs to ensure all file handles are\n// flushed and closed before checkpoint writes begin.\nfunc WaitForWALStagingDrain() {\n\twalStagingWg.Wait()\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete. Each request is routed to the\n// shard that owns the host directory.\n//\n// If shutdown is in progress (WAL staging goroutines may have exited),\n// rotation is skipped to avoid deadlocking on abandoned channels.\nfunc RotateWALFiles(hostDirs []string) {\n\tif walShardRotateChs == nil || walShuttingDown.Load() {\n\t\treturn\n\t}\n\tdeadline := time.After(2 * time.Minute)\n\tdones := make([]chan struct{}, 0, len(hostDirs))\n\tfor _, dir := range hostDirs {\n\t\tdone := make(chan struct{})\n\t\tshard := walShardIndexFromDir(dir)\n\t\tselect {\n\t\tcase walShardRotateChs[shard] <- walRotateReq{hostDir: dir, done: done}:\n\t\t\tdones = append(dones, done)\n\t\tcase <-deadline:\n\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL rotation send timed out, %d of %d hosts remaining\",\n\t\t\t\tlen(hostDirs)-len(dones), len(hostDirs))\n\t\t\tgoto waitDones\n\t\t}\n\t}\nwaitDones:\n\tfor _, done := range dones {\n\t\tselect {\n\t\tcase <-done:\n\t\tcase <-time.After(30 * time.Second):\n\t\t\tcclog.Warn(\"[METRICSTORE]> WAL rotation completion timed out, continuing\")\n\t\t\treturn\n\t\t}\n\t}\n}\n\n// walShardIndexFromDir extracts cluster and node from a host directory path\n// and returns the shard index. The path format is: rootDir/cluster/node\nfunc walShardIndexFromDir(hostDir string) int {\n\t// hostDir = .../cluster/node — extract last two path components\n\tnode := path.Base(hostDir)\n\tcluster := path.Base(path.Dir(hostDir))\n\treturn walShardIndex(cluster, node)\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFilesAfterShutdown(hostDirs []string) {\n\tfor _, dir := range hostDirs {\n\t\twalPath := path.Join(dir, \"current.wal\")\n\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t}\n\t}\n}\n\n// writeWALRecordDirect encodes a WAL record into a contiguous buffer first,\n// then writes it to the bufio.Writer in a single call. This prevents partial\n// records in the write buffer if a write error occurs mid-record (e.g. disk full).\n// Returns the number of bytes written and any error.\nfunc writeWALRecordDirect(w *bufio.Writer, msg *WALMessage) (int, error) {\n\t// Compute payload and total record size.\n\tpayloadSize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tpayloadSize += 1 + len(s)\n\t}\n\t// Total: 8 (header) + payload + 4 (CRC).\n\ttotalSize := 8 + payloadSize + 4\n\n\t// Use stack buffer for typical small records, heap-allocate only for large ones.\n\tvar stackBuf [256]byte\n\tvar buf []byte\n\tif totalSize <= len(stackBuf) {\n\t\tbuf = stackBuf[:totalSize]\n\t} else {\n\t\tbuf = make([]byte, totalSize)\n\t}\n\n\t// Header: magic + payload length.\n\tbinary.LittleEndian.PutUint32(buf[0:4], walRecordMagic)\n\tbinary.LittleEndian.PutUint32(buf[4:8], uint32(payloadSize))\n\n\t// Payload starts at offset 8.\n\tp := 8\n\n\t// Timestamp (8 bytes).\n\tbinary.LittleEndian.PutUint64(buf[p:p+8], uint64(msg.Timestamp))\n\tp += 8\n\n\t// Metric name length (2 bytes) + metric name.\n\tbinary.LittleEndian.PutUint16(buf[p:p+2], uint16(len(msg.MetricName)))\n\tp += 2\n\tp += copy(buf[p:], msg.MetricName)\n\n\t// Selector count (1 byte).\n\tbuf[p] = byte(len(msg.Selector))\n\tp++\n\n\t// Selectors (1-byte length + bytes each).\n\tfor _, sel := range msg.Selector {\n\t\tbuf[p] = byte(len(sel))\n\t\tp++\n\t\tp += copy(buf[p:], sel)\n\t}\n\n\t// Value (4 bytes, float32 bits).\n\tbinary.LittleEndian.PutUint32(buf[p:p+4], math.Float32bits(float32(msg.Value)))\n\tp += 4\n\n\t// CRC32 over payload (bytes 8..8+payloadSize).\n\tcrc := crc32.ChecksumIEEE(buf[8 : 8+payloadSize])\n\tbinary.LittleEndian.PutUint32(buf[p:p+4], crc)\n\n\t// Single atomic write to the buffered writer.\n\tn, err := w.Write(buf)\n\treturn n, err\n}\n\n// readWALRecord reads one WAL record from the reader.\n// Returns (nil, nil) on clean EOF. Returns error on data corruption.\n// A CRC mismatch indicates a truncated trailing record (expected on crash).\nfunc readWALRecord(r io.Reader) (*WALMessage, error) {\n\tvar magic uint32\n\tif err := binary.Read(r, binary.LittleEndian, &magic); err != nil {\n\t\tif err == io.EOF {\n\t\t\treturn nil, nil // Clean EOF\n\t\t}\n\t\treturn nil, fmt.Errorf(\"read record magic: %w\", err)\n\t}\n\n\tif magic != walRecordMagic {\n\t\treturn nil, fmt.Errorf(\"invalid record magic 0x%08X (expected 0x%08X)\", magic, walRecordMagic)\n\t}\n\n\tvar payloadLen uint32\n\tif err := binary.Read(r, binary.LittleEndian, &payloadLen); err != nil {\n\t\treturn nil, fmt.Errorf(\"read payload length: %w\", err)\n\t}\n\n\tif payloadLen > 1<<20 { // 1 MB sanity limit\n\t\treturn nil, fmt.Errorf(\"record payload too large: %d bytes\", payloadLen)\n\t}\n\n\tpayload := make([]byte, payloadLen)\n\tif _, err := io.ReadFull(r, payload); err != nil {\n\t\treturn nil, fmt.Errorf(\"read payload: %w\", err)\n\t}\n\n\tvar storedCRC uint32\n\tif err := binary.Read(r, binary.LittleEndian, &storedCRC); err != nil {\n\t\treturn nil, fmt.Errorf(\"read CRC: %w\", err)\n\t}\n\n\tif crc32.ChecksumIEEE(payload) != storedCRC {\n\t\treturn nil, fmt.Errorf(\"CRC mismatch (truncated write or corruption)\")\n\t}\n\n\treturn parseWALPayload(payload)\n}\n\n// parseWALPayload decodes a binary payload into a WALMessage.\nfunc parseWALPayload(payload []byte) (*WALMessage, error) {\n\tif len(payload) < 8+2+1+4 {\n\t\treturn nil, fmt.Errorf(\"payload too short: %d bytes\", len(payload))\n\t}\n\n\toffset := 0\n\n\t// Timestamp (8 bytes)\n\tts := int64(binary.LittleEndian.Uint64(payload[offset : offset+8]))\n\toffset += 8\n\n\t// Metric name (2-byte length + bytes)\n\tif offset+2 > len(payload) {\n\t\treturn nil, fmt.Errorf(\"metric name length overflows payload\")\n\t}\n\tmLen := int(binary.LittleEndian.Uint16(payload[offset : offset+2]))\n\toffset += 2\n\n\tif offset+mLen > len(payload) {\n\t\treturn nil, fmt.Errorf(\"metric name overflows payload\")\n\t}\n\tmetricName := string(payload[offset : offset+mLen])\n\toffset += mLen\n\n\t// Selector count (1 byte)\n\tif offset >= len(payload) {\n\t\treturn nil, fmt.Errorf(\"selector count overflows payload\")\n\t}\n\tselCount := int(payload[offset])\n\toffset++\n\n\tselectors := make([]string, selCount)\n\tfor i := range selCount {\n\t\tif offset >= len(payload) {\n\t\t\treturn nil, fmt.Errorf(\"selector[%d] length overflows payload\", i)\n\t\t}\n\t\tsLen := int(payload[offset])\n\t\toffset++\n\n\t\tif offset+sLen > len(payload) {\n\t\t\treturn nil, fmt.Errorf(\"selector[%d] data overflows payload\", i)\n\t\t}\n\t\tselectors[i] = string(payload[offset : offset+sLen])\n\t\toffset += sLen\n\t}\n\n\t// Value (4 bytes, float32 bits)\n\tif offset+4 > len(payload) {\n\t\treturn nil, fmt.Errorf(\"value overflows payload\")\n\t}\n\tbits := binary.LittleEndian.Uint32(payload[offset : offset+4])\n\tvalue := schema.Float(math.Float32frombits(bits))\n\n\treturn &WALMessage{\n\t\tMetricName: metricName,\n\t\tTimestamp: ts,\n\t\tSelector: selectors,\n\t\tValue: value,\n\t}, nil\n}\n\n// loadWALFile reads a WAL file and replays all valid records into the Level tree.\n// l is the host-level node. Corrupt or partial trailing records are silently skipped\n// (expected on crash). Records older than 'from' are skipped.\nfunc (l *Level) loadWALFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\n\t// Verify file header magic.\n\tvar fileMagic uint32\n\tif err := binary.Read(br, binary.LittleEndian, &fileMagic); err != nil {\n\t\tif err == io.EOF {\n\t\t\treturn nil // Empty file, no data\n\t\t}\n\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: read file header: %w\", err)\n\t}\n\n\tif fileMagic != walFileMagic {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: invalid file magic 0x%08X (expected 0x%08X)\", fileMagic, walFileMagic)\n\t}\n\n\t// Cache level lookups to avoid repeated tree traversal.\n\tlvlCache := make(map[string]*Level)\n\n\tfor {\n\t\tmsg, err := readWALRecord(br)\n\t\tif err != nil {\n\t\t\t// Truncated trailing record is expected after a crash; stop replaying.\n\t\t\tcclog.Debugf(\"[METRICSTORE]> WAL: stopping replay at corrupted/partial record: %v\", err)\n\t\t\tbreak\n\t\t}\n\t\tif msg == nil {\n\t\t\tbreak // Clean EOF\n\t\t}\n\n\t\tif msg.Timestamp < from {\n\t\t\tcontinue // Older than retention window\n\t\t}\n\n\t\tminfo, ok := m.Metrics[msg.MetricName]\n\t\tif !ok {\n\t\t\tcontinue // Unknown metric (config may have changed)\n\t\t}\n\n\t\t// Cache key is the null-separated selector path.\n\t\tcacheKey := joinSelector(msg.Selector)\n\t\tlvl, ok := lvlCache[cacheKey]\n\t\tif !ok {\n\t\t\tlvl = l.findLevelOrCreate(msg.Selector, len(m.Metrics))\n\t\t\tlvlCache[cacheKey] = lvl\n\t\t}\n\n\t\t// Write directly to the buffer, same as WriteToLevel but without the\n\t\t// global level lookup (we already have the right level).\n\t\tlvl.lock.Lock()\n\t\tb := lvl.metrics[minfo.offset]\n\t\tif b == nil {\n\t\t\tb = newBuffer(msg.Timestamp, minfo.Frequency)\n\t\t\tlvl.metrics[minfo.offset] = b\n\t\t}\n\t\tnb, writeErr := b.write(msg.Timestamp, msg.Value)\n\t\tif writeErr == nil && b != nb {\n\t\t\tlvl.metrics[minfo.offset] = nb\n\t\t}\n\t\t// Ignore write errors for timestamps before buffer start (can happen when\n\t\t// replaying WAL entries that predate a loaded snapshot's start time).\n\t\tlvl.lock.Unlock()\n\t}\n\n\treturn nil\n}\n\n// joinSelector builds a cache key from a selector slice using null bytes as separators.\nfunc joinSelector(sel []string) string {\n\tif len(sel) == 0 {\n\t\treturn \"\"\n\t}\n\tvar result strings.Builder\n\tresult.WriteString(sel[0])\n\tfor i := 1; i < len(sel); i++ {\n\t\tresult.WriteString(\"\\x00\" + sel[i])\n\t}\n\treturn result.String()\n}\n\n// ToCheckpointWAL writes binary snapshot files for all hosts in parallel.\n// Returns the number of files written, the list of host directories that were\n// successfully checkpointed (for WAL rotation), and any errors.\nfunc (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string, error) {\n\t// Collect all cluster/host pairs.\n\tm.root.lock.RLock()\n\ttotalHosts := 0\n\tfor _, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\ttotalHosts += len(l1.children)\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\tlevels := make([]*Level, 0, totalHosts)\n\tselectors := make([][]string, 0, totalHosts)\n\n\tm.root.lock.RLock()\n\tfor sel1, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\tfor sel2, l2 := range l1.children {\n\t\t\tlevels = append(levels, l2)\n\t\t\tselectors = append(selectors, []string{sel1, sel2})\n\t\t}\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\ttype workItem struct {\n\t\tlevel *Level\n\t\thostDir string\n\t\tselector []string\n\t}\n\n\ttotalWork := len(levels)\n\tcclog.Infof(\"[METRICSTORE]> Starting binary checkpoint for %d hosts with %d workers\", totalWork, Keys.NumWorkers)\n\n\tn, errs, completed := int32(0), int32(0), int32(0)\n\tvar successDirs []string\n\tvar successMu sync.Mutex\n\n\tvar wg sync.WaitGroup\n\twg.Add(Keys.NumWorkers)\n\twork := make(chan workItem, Keys.NumWorkers*2)\n\n\t// Progress logging goroutine.\n\tstopProgress := make(chan struct{})\n\tgo func() {\n\t\tticker := time.NewTicker(10 * time.Second)\n\t\tdefer ticker.Stop()\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ticker.C:\n\t\t\t\tcclog.Infof(\"[METRICSTORE]> Checkpoint progress: %d/%d hosts (%d written, %d errors)\",\n\t\t\t\t\tatomic.LoadInt32(&completed), totalWork, atomic.LoadInt32(&n), atomic.LoadInt32(&errs))\n\t\t\tcase <-stopProgress:\n\t\t\t\treturn\n\t\t\t}\n\t\t}\n\t}()\n\n\tfor range Keys.NumWorkers {\n\t\tgo func() {\n\t\t\tdefer wg.Done()\n\t\t\tfor wi := range work {\n\t\t\t\terr := wi.level.toCheckpointBinary(wi.hostDir, from, to, m)\n\t\t\t\tif err != nil {\n\t\t\t\t\tif err == ErrNoNewArchiveData {\n\t\t\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t\t\t\tcontinue\n\t\t\t\t\t}\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpoint error for %s: %v\", wi.hostDir, err)\n\t\t\t\t\tatomic.AddInt32(&errs, 1)\n\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n\t\t\t\t\t}\n\t\t\t\t\tsuccessMu.Lock()\n\t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n\t\t\t\t\tsuccessMu.Unlock()\n\t\t\t\t}\n\t\t\t\tatomic.AddInt32(&completed, 1)\n\t\t\t}\n\t\t}()\n\t}\n\n\tfor i := range levels {\n\t\thostDir := path.Join(dir, path.Join(selectors[i]...))\n\t\twork <- workItem{\n\t\t\tlevel: levels[i],\n\t\t\thostDir: hostDir,\n\t\t\tselector: selectors[i],\n\t\t}\n\t}\n\tclose(work)\n\twg.Wait()\n\tclose(stopProgress)\n\n\tif errs > 0 {\n\t\treturn int(n), successDirs, fmt.Errorf(\"[METRICSTORE]> %d errors during binary checkpoint (%d successes)\", errs, n)\n\t}\n\treturn int(n), successDirs, nil\n}\n\n// toCheckpointBinary writes a binary snapshot file for a single host-level node.\n// Uses atomic rename (write to .tmp then rename) to avoid partial reads on crash.\nfunc (l *Level) toCheckpointBinary(dir string, from, to int64, m *MemoryStore) error {\n\tcf, err := l.toCheckpointFile(from, to, m)\n\tif err != nil {\n\t\treturn err\n\t}\n\tif cf == nil {\n\t\treturn ErrNoNewArchiveData\n\t}\n\n\tif err := os.MkdirAll(dir, CheckpointDirPerms); err != nil {\n\t\treturn fmt.Errorf(\"mkdir %s: %w\", dir, err)\n\t}\n\n\t// Write to a temp file first, then rename (atomic on POSIX).\n\ttmpPath := path.Join(dir, fmt.Sprintf(\"%d.bin.tmp\", from))\n\tfinalPath := path.Join(dir, fmt.Sprintf(\"%d.bin\", from))\n\n\tf, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"open binary snapshot %s: %w\", tmpPath, err)\n\t}\n\n\tbw := bufio.NewWriter(f)\n\tif err := writeBinarySnapshotFile(bw, cf); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn fmt.Errorf(\"write binary snapshot: %w\", err)\n\t}\n\tif err := bw.Flush(); err != nil {\n\t\tf.Close()\n\t\tos.Remove(tmpPath)\n\t\treturn err\n\t}\n\tf.Close()\n\n\treturn os.Rename(tmpPath, finalPath)\n}\n\n// writeBinarySnapshotFile writes the binary snapshot file header and level tree.\nfunc writeBinarySnapshotFile(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, snapFileMagic); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.From); err != nil {\n\t\treturn err\n\t}\n\tif err := binary.Write(w, binary.LittleEndian, cf.To); err != nil {\n\t\treturn err\n\t}\n\treturn writeBinaryLevel(w, cf)\n}\n\n// writeBinaryLevel recursively writes a CheckpointFile level in binary format.\nfunc writeBinaryLevel(w io.Writer, cf *CheckpointFile) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Metrics))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, metric := range cf.Metrics {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Frequency); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, metric.Start); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(metric.Data))); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tfor _, v := range metric.Data {\n\t\t\tif err := binary.Write(w, binary.LittleEndian, math.Float32bits(float32(v))); err != nil {\n\t\t\t\treturn err\n\t\t\t}\n\t\t}\n\t}\n\n\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Children))); err != nil {\n\t\treturn err\n\t}\n\n\tfor name, child := range cf.Children {\n\t\tif err := writeString16(w, name); err != nil {\n\t\t\treturn err\n\t\t}\n\t\tif err := writeBinaryLevel(w, child); err != nil {\n\t\t\treturn err\n\t\t}\n\t}\n\n\treturn nil\n}\n\n// writeString16 writes a 2-byte length-prefixed string to w.\nfunc writeString16(w io.Writer, s string) error {\n\tif err := binary.Write(w, binary.LittleEndian, uint16(len(s))); err != nil {\n\t\treturn err\n\t}\n\t_, err := io.WriteString(w, s)\n\treturn err\n}\n\n// loadBinaryFile reads a binary snapshot file and loads data into the Level tree.\n// The retention check (from) is applied to the file's 'to' timestamp.\nfunc (l *Level) loadBinaryFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\n\tvar magic uint32\n\tif err := binary.Read(br, binary.LittleEndian, &magic); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read magic: %w\", err)\n\t}\n\tif magic != snapFileMagic {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: invalid magic 0x%08X (expected 0x%08X)\", magic, snapFileMagic)\n\t}\n\n\tvar fileFrom, fileTo int64\n\tif err := binary.Read(br, binary.LittleEndian, &fileFrom); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read from: %w\", err)\n\t}\n\tif err := binary.Read(br, binary.LittleEndian, &fileTo); err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read to: %w\", err)\n\t}\n\n\tif fileTo != 0 && fileTo < from {\n\t\treturn nil // File is older than retention window, skip it\n\t}\n\n\tcf, err := readBinaryLevel(br)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read level tree: %w\", err)\n\t}\n\tcf.From = fileFrom\n\tcf.To = fileTo\n\n\treturn l.loadFile(cf, m)\n}\n\n// readBinaryLevel recursively reads a level from the binary snapshot format.\nfunc readBinaryLevel(r io.Reader) (*CheckpointFile, error) {\n\tcf := &CheckpointFile{\n\t\tMetrics: make(map[string]*CheckpointMetrics),\n\t\tChildren: make(map[string]*CheckpointFile),\n\t}\n\n\tvar numMetrics uint32\n\tif err := binary.Read(r, binary.LittleEndian, &numMetrics); err != nil {\n\t\treturn nil, fmt.Errorf(\"read num_metrics: %w\", err)\n\t}\n\n\tfor range numMetrics {\n\t\tname, err := readString16(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read metric name: %w\", err)\n\t\t}\n\n\t\tvar freq, start int64\n\t\tif err := binary.Read(r, binary.LittleEndian, &freq); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read frequency for %s: %w\", name, err)\n\t\t}\n\t\tif err := binary.Read(r, binary.LittleEndian, &start); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read start for %s: %w\", name, err)\n\t\t}\n\n\t\tvar numValues uint32\n\t\tif err := binary.Read(r, binary.LittleEndian, &numValues); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read num_values for %s: %w\", name, err)\n\t\t}\n\n\t\tdata := make([]schema.Float, numValues)\n\t\tfor i := range numValues {\n\t\t\tvar bits uint32\n\t\t\tif err := binary.Read(r, binary.LittleEndian, &bits); err != nil {\n\t\t\t\treturn nil, fmt.Errorf(\"read value[%d] for %s: %w\", i, name, err)\n\t\t\t}\n\t\t\tdata[i] = schema.Float(math.Float32frombits(bits))\n\t\t}\n\n\t\tcf.Metrics[name] = &CheckpointMetrics{\n\t\t\tFrequency: freq,\n\t\t\tStart: start,\n\t\t\tData: data,\n\t\t}\n\t}\n\n\tvar numChildren uint32\n\tif err := binary.Read(r, binary.LittleEndian, &numChildren); err != nil {\n\t\treturn nil, fmt.Errorf(\"read num_children: %w\", err)\n\t}\n\n\tfor range numChildren {\n\t\tchildName, err := readString16(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read child name: %w\", err)\n\t\t}\n\n\t\tchild, err := readBinaryLevel(r)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"read child %s: %w\", childName, err)\n\t\t}\n\t\tcf.Children[childName] = child\n\t}\n\n\treturn cf, nil\n}\n\n// readString16 reads a 2-byte length-prefixed string from r.\nfunc readString16(r io.Reader) (string, error) {\n\tvar sLen uint16\n\tif err := binary.Read(r, binary.LittleEndian, &sLen); err != nil {\n\t\treturn \"\", err\n\t}\n\tbuf := make([]byte, sLen)\n\tif _, err := io.ReadFull(r, buf); err != nil {\n\t\treturn \"\", err\n\t}\n\treturn string(buf), nil\n}\n","structuredPatch":[{"oldStart":735,"oldLines":11,"newStart":735,"newLines":6,"lines":[" atomic.AddInt32(&errs, 1)"," } else {"," atomic.AddInt32(&n, 1)","- // Delete WAL immediately after successful snapshot.","- walPath := path.Join(wi.hostDir, \"current.wal\")","- if err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {","- cclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)","- }"," successMu.Lock()"," successDirs = append(successDirs, wi.hostDir)"," successMu.Unlock()"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"4a04d73e-3bda-470e-a534-b37af80f7c77","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"029e1b61-4f3a-48d4-a30a-7d98e00c7cca","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_0124dgeToyDPwCuCNZ2pWaqg","type":"message","role":"assistant","content":[{"type":"text","text":"**Step 3: Set/clear flag around checkpoint** in `checkpoint.go`:"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":346,"cache_read_input_tokens":53320,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":346},"output_tokens":1,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7Y848kQYE2iedNsp7n","type":"assistant","uuid":"18b2bd48-ae12-40f4-8ba8-51075b938a75","timestamp":"2026-03-29T09:12:14.932Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"18b2bd48-ae12-40f4-8ba8-51075b938a75","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_0124dgeToyDPwCuCNZ2pWaqg","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01Svt2DbYzRG4fjhvpgnLDxH","name":"Read","input":{"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go","limit":40,"offset":120},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":346,"cache_read_input_tokens":53320,"output_tokens":132,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":346,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7Y848kQYE2iedNsp7n","type":"assistant","uuid":"173abc8b-4532-4d3e-8697-24efbd26299f","timestamp":"2026-03-29T09:12:15.603Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"173abc8b-4532-4d3e-8697-24efbd26299f","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01Svt2DbYzRG4fjhvpgnLDxH","type":"tool_result","content":"120\t\t\t\tcase <-ticker.C:\n121\t\t\t\t\tlastCheckpointMu.Lock()\n122\t\t\t\t\tfrom := lastCheckpoint\n123\t\t\t\t\tlastCheckpointMu.Unlock()\n124\t\n125\t\t\t\t\tnow := time.Now()\n126\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> start checkpointing (starting at %s)...\", from.Format(time.RFC3339))\n127\t\n128\t\t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n129\t\t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n130\t\t\t\t\t\tif err != nil {\n131\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n132\t\t\t\t\t\t}\n133\t\t\t\t\t\tif n > 0 {\n134\t\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n135\t\t\t\t\t\t\tlastCheckpointMu.Lock()\n136\t\t\t\t\t\t\tlastCheckpoint = now\n137\t\t\t\t\t\t\tlastCheckpointMu.Unlock()\n138\t\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n139\t\t\t\t\t\t\tRotateWALFiles(hostDirs)\n140\t\t\t\t\t\t}\n141\t\t\t\t\t} else {\n142\t\t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n143\t\t\t\t\t\tif err != nil {\n144\t\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> checkpointing failed: %s\", err.Error())\n145\t\t\t\t\t\t} else {\n146\t\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d checkpoint files created\", n)\n147\t\t\t\t\t\t\tlastCheckpointMu.Lock()\n148\t\t\t\t\t\t\tlastCheckpoint = now\n149\t\t\t\t\t\t\tlastCheckpointMu.Unlock()\n150\t\t\t\t\t\t}\n151\t\t\t\t\t}\n152\t\t\t\t}\n153\t\t\t}\n154\t\t})\n155\t}\n156\t\n157\t// MarshalJSON provides optimized JSON encoding for CheckpointMetrics.\n158\t//\n159\t// Since schema.Float has custom MarshalJSON, serializing []Float has significant overhead."}]},"uuid":"20fda423-1a00-47da-8533-f47ad5e2e356","timestamp":"2026-03-29T09:12:15.613Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go","content":"\t\t\tcase <-ticker.C:\n\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\tfrom := lastCheckpoint\n\t\t\t\tlastCheckpointMu.Unlock()\n\n\t\t\t\tnow := time.Now()\n\t\t\t\tcclog.Infof(\"[METRICSTORE]> start checkpointing (starting at %s)...\", from.Format(time.RFC3339))\n\n\t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n\t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n\t\t\t\t\t}\n\t\t\t\t\tif n > 0 {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n\t\t\t\t\t\tRotateWALFiles(hostDirs)\n\t\t\t\t\t}\n\t\t\t\t} else {\n\t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> checkpointing failed: %s\", err.Error())\n\t\t\t\t\t} else {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d checkpoint files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\t})\n}\n\n// MarshalJSON provides optimized JSON encoding for CheckpointMetrics.\n//\n// Since schema.Float has custom MarshalJSON, serializing []Float has significant overhead.","numLines":40,"startLine":120,"totalLines":671}},"sourceToolAssistantUUID":"173abc8b-4532-4d3e-8697-24efbd26299f","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"20fda423-1a00-47da-8533-f47ad5e2e356","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_013EquakTBjkBBUdyC5fSkh4","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01RVRZBamYi4kpXgcedRo7XG","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/checkpoint.go","old_string":"\t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n\t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n\t\t\t\t\t}\n\t\t\t\t\tif n > 0 {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n\t\t\t\t\t\tRotateWALFiles(hostDirs)\n\t\t\t\t\t}\n\t\t\t\t} else {","new_string":"\t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n\t\t\t\t\t// Pause WAL writes: the binary snapshot captures all in-memory\n\t\t\t\t\t// data, so WAL records written during checkpoint are redundant\n\t\t\t\t\t// and would be deleted during rotation anyway.\n\t\t\t\t\twalCheckpointActive.Store(true)\n\t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n\t\t\t\t\t}\n\t\t\t\t\tif n > 0 {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n\t\t\t\t\t\tRotateWALFiles(hostDirs)\n\t\t\t\t\t}\n\t\t\t\t\twalCheckpointActive.Store(false)\n\t\t\t\t\twalDropped.Store(0)\n\t\t\t\t} else 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in-memory\n\t\t\t\t\t// data, so WAL records written during checkpoint are redundant\n\t\t\t\t\t// and would be deleted during rotation anyway.\n\t\t\t\t\twalCheckpointActive.Store(true)\n\t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n\t\t\t\t\t}\n\t\t\t\t\tif n > 0 {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n\t\t\t\t\t\tRotateWALFiles(hostDirs)\n\t\t\t\t\t}\n\t\t\t\t\twalCheckpointActive.Store(false)\n\t\t\t\t\twalDropped.Store(0)\n\t\t\t\t} else {","originalFile":"// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.\n// All rights reserved. This file is part of cc-backend.\n// Use of this source code is governed by a MIT-style\n// license that can be found in the LICENSE file.\n\n// This file implements checkpoint persistence for the in-memory metric store.\n//\n// Checkpoints enable graceful restarts by periodically saving in-memory metric\n// data to disk in JSON or binary format. The checkpoint system:\n//\n// Key Features:\n// - Periodic background checkpointing via the Checkpointing() worker\n// - Two format families: JSON (human-readable) and WAL+binary (compact, crash-safe)\n// - Parallel checkpoint creation and loading using worker pools\n// - Hierarchical file organization: checkpoint_dir/cluster/host/timestamp.{json|bin}\n// - WAL file: checkpoint_dir/cluster/host/current.wal (append-only, per-entry)\n// - Only saves unarchived data (archived data is already persisted elsewhere)\n// - GC optimization during loading to prevent excessive heap growth\n//\n// Checkpoint Workflow:\n// 1. Init() loads checkpoints within retention window at startup\n// 2. Checkpointing() worker periodically saves new data\n// 3. Shutdown() writes final checkpoint before exit\n//\n// File Organization:\n//\n//\tcheckpoints/\n//\t cluster1/\n//\t host001/\n//\t 1234567890.json (JSON format: full subtree snapshot)\n//\t 1234567890.bin (binary format: full subtree snapshot)\n//\t current.wal (WAL format: append-only per-entry log)\n//\t host002/\n//\t ...\npackage metricstore\n\nimport (\n\t\"bufio\"\n\t\"context\"\n\t\"encoding/json\"\n\t\"errors\"\n\t\"fmt\"\n\t\"io/fs\"\n\t\"os\"\n\t\"path\"\n\t\"path/filepath\"\n\t\"sort\"\n\t\"strconv\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\n\t\"time\"\n\n\tcclog \"github.com/ClusterCockpit/cc-lib/v2/ccLogger\"\n\t\"github.com/ClusterCockpit/cc-lib/v2/schema\"\n)\n\nconst (\n\tCheckpointFilePerms = 0o644 // File permissions for checkpoint files\n\tCheckpointDirPerms = 0o755 // Directory permissions for checkpoint directories\n\tGCTriggerInterval = DefaultGCTriggerInterval // Interval for triggering GC during checkpoint loading\n)\n\n// CheckpointMetrics represents metric data in a checkpoint file.\n// Whenever the structure changes, update MarshalJSON as well!\ntype CheckpointMetrics struct {\n\tData []schema.Float `json:\"data\"`\n\tFrequency int64 `json:\"frequency\"`\n\tStart int64 `json:\"start\"`\n}\n\n// CheckpointFile represents the hierarchical structure of a checkpoint file.\n// It mirrors the Level tree structure from the MemoryStore.\ntype CheckpointFile struct {\n\tMetrics map[string]*CheckpointMetrics `json:\"metrics\"`\n\tChildren map[string]*CheckpointFile `json:\"children\"`\n\tFrom int64 `json:\"from\"`\n\tTo int64 `json:\"to\"`\n}\n\n// lastCheckpoint tracks the timestamp of the last checkpoint creation.\nvar (\n\tlastCheckpoint time.Time\n\tlastCheckpointMu sync.Mutex\n)\n\n// Checkpointing starts a background worker that periodically saves metric data to disk.\n//\n// Checkpoints are written every 12 hours (hardcoded).\n//\n// Format behaviour:\n// - \"json\": Periodic checkpointing every checkpointInterval\n// - \"wal\": Periodic binary snapshots + WAL rotation every checkpointInterval\nfunc Checkpointing(wg *sync.WaitGroup, ctx context.Context) {\n\tlastCheckpointMu.Lock()\n\tlastCheckpoint = time.Now()\n\tlastCheckpointMu.Unlock()\n\n\tms := GetMemoryStore()\n\n\twg.Go(func() {\n\n\t\td := 12 * time.Hour // default checkpoint interval\n\t\tif Keys.CheckpointInterval != \"\" {\n\t\t\tparsed, err := time.ParseDuration(Keys.CheckpointInterval)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> invalid checkpoint-interval %q: %s, using default 12h\", Keys.CheckpointInterval, err)\n\t\t\t} else {\n\t\t\t\td = parsed\n\t\t\t}\n\t\t}\n\n\t\tticker := time.NewTicker(d)\n\t\tdefer ticker.Stop()\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\treturn\n\t\t\tcase <-ticker.C:\n\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\tfrom := lastCheckpoint\n\t\t\t\tlastCheckpointMu.Unlock()\n\n\t\t\t\tnow := time.Now()\n\t\t\t\tcclog.Infof(\"[METRICSTORE]> start checkpointing (starting at %s)...\", from.Format(time.RFC3339))\n\n\t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n\t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n\t\t\t\t\t}\n\t\t\t\t\tif n > 0 {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d binary snapshot files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n\t\t\t\t\t\tRotateWALFiles(hostDirs)\n\t\t\t\t\t}\n\t\t\t\t} else {\n\t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n\t\t\t\t\tif err != nil {\n\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> checkpointing failed: %s\", err.Error())\n\t\t\t\t\t} else {\n\t\t\t\t\t\tcclog.Infof(\"[METRICSTORE]> done: %d checkpoint files created\", n)\n\t\t\t\t\t\tlastCheckpointMu.Lock()\n\t\t\t\t\t\tlastCheckpoint = now\n\t\t\t\t\t\tlastCheckpointMu.Unlock()\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\t})\n}\n\n// MarshalJSON provides optimized JSON encoding for CheckpointMetrics.\n//\n// Since schema.Float has custom MarshalJSON, serializing []Float has significant overhead.\n// This method manually constructs JSON to avoid allocations and interface conversions.\nfunc (cm *CheckpointMetrics) MarshalJSON() ([]byte, error) {\n\tbuf := make([]byte, 0, 128+len(cm.Data)*8)\n\tbuf = append(buf, `{\"frequency\":`...)\n\tbuf = strconv.AppendInt(buf, cm.Frequency, 10)\n\tbuf = append(buf, `,\"start\":`...)\n\tbuf = strconv.AppendInt(buf, cm.Start, 10)\n\tbuf = append(buf, `,\"data\":[`...)\n\tfor i, x := range cm.Data {\n\t\tif i != 0 {\n\t\t\tbuf = append(buf, ',')\n\t\t}\n\t\tif x.IsNaN() {\n\t\t\tbuf = append(buf, `null`...)\n\t\t} else {\n\t\t\tbuf = strconv.AppendFloat(buf, float64(x), 'f', 1, 32)\n\t\t}\n\t}\n\tbuf = append(buf, `]}`...)\n\treturn buf, nil\n}\n\n// ToCheckpoint writes metric data to checkpoint files in parallel (JSON format).\n//\n// Metrics at root and cluster levels are skipped. One file per host is created.\n// Uses worker pool (Keys.NumWorkers) for parallel processing. Only locks one host\n// at a time, allowing concurrent writes/reads to other hosts.\n//\n// Returns the number of checkpoint files created and any errors encountered.\nfunc (m *MemoryStore) ToCheckpoint(dir string, from, to int64) (int, error) {\n\t// Pre-calculate capacity by counting cluster/host pairs\n\tm.root.lock.RLock()\n\ttotalHosts := 0\n\tfor _, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\ttotalHosts += len(l1.children)\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\tlevels := make([]*Level, 0, totalHosts)\n\tselectors := make([][]string, 0, totalHosts)\n\n\tm.root.lock.RLock()\n\tfor sel1, l1 := range m.root.children {\n\t\tl1.lock.RLock()\n\t\tfor sel2, l2 := range l1.children {\n\t\t\tlevels = append(levels, l2)\n\t\t\tselectors = append(selectors, []string{sel1, sel2})\n\t\t}\n\t\tl1.lock.RUnlock()\n\t}\n\tm.root.lock.RUnlock()\n\n\ttype workItem struct {\n\t\tlevel *Level\n\t\tdir string\n\t\tselector []string\n\t}\n\n\tn, errs := int32(0), int32(0)\n\n\tvar wg sync.WaitGroup\n\twg.Add(Keys.NumWorkers)\n\twork := make(chan workItem, Keys.NumWorkers*2)\n\tfor worker := 0; worker < Keys.NumWorkers; worker++ {\n\t\tgo func() {\n\t\t\tdefer wg.Done()\n\n\t\t\tfor workItem := range work {\n\t\t\t\tif err := workItem.level.toCheckpoint(workItem.dir, from, to, m); err != nil {\n\t\t\t\t\tif err == ErrNoNewArchiveData {\n\t\t\t\t\t\tcontinue\n\t\t\t\t\t}\n\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> error while checkpointing %#v: %s\", workItem.selector, err.Error())\n\t\t\t\t\tatomic.AddInt32(&errs, 1)\n\t\t\t\t} else {\n\t\t\t\t\tatomic.AddInt32(&n, 1)\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\t}\n\n\tfor i := 0; i < len(levels); i++ {\n\t\tdir := path.Join(dir, path.Join(selectors[i]...))\n\t\twork <- workItem{\n\t\t\tlevel: levels[i],\n\t\t\tdir: dir,\n\t\t\tselector: selectors[i],\n\t\t}\n\t}\n\n\tclose(work)\n\twg.Wait()\n\n\tif errs > 0 {\n\t\treturn int(n), fmt.Errorf(\"[METRICSTORE]> %d errors happened while creating checkpoints (%d successes)\", errs, n)\n\t}\n\treturn int(n), nil\n}\n\n// toCheckpointFile recursively converts a Level tree to CheckpointFile structure.\n// Skips metrics that are already archived. Returns nil if no unarchived data exists.\nfunc (l *Level) toCheckpointFile(from, to int64, m *MemoryStore) (*CheckpointFile, error) {\n\tl.lock.RLock()\n\tdefer l.lock.RUnlock()\n\n\tretval := &CheckpointFile{\n\t\tFrom: from,\n\t\tTo: to,\n\t\tMetrics: make(map[string]*CheckpointMetrics),\n\t\tChildren: make(map[string]*CheckpointFile),\n\t}\n\n\tfor metric, minfo := range m.Metrics {\n\t\tb := l.metrics[minfo.offset]\n\t\tif b == nil {\n\t\t\tcontinue\n\t\t}\n\n\t\tallArchived := true\n\t\tb.iterFromTo(from, to, func(b *buffer) error {\n\t\t\tif !b.archived {\n\t\t\t\tallArchived = false\n\t\t\t\treturn fmt.Errorf(\"stop\") // Early termination signal\n\t\t\t}\n\t\t\treturn nil\n\t\t})\n\n\t\tif allArchived {\n\t\t\tcontinue\n\t\t}\n\n\t\tdata := make([]schema.Float, (to-from)/b.frequency+1)\n\t\tdata, start, end, err := b.read(from, to, data)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\n\t\tfor i := int((end - start) / b.frequency); i < len(data); i++ {\n\t\t\tdata[i] = schema.NaN\n\t\t}\n\n\t\tretval.Metrics[metric] = &CheckpointMetrics{\n\t\t\tFrequency: b.frequency,\n\t\t\tStart: start,\n\t\t\tData: data,\n\t\t}\n\t}\n\n\tfor name, child := range l.children {\n\t\tval, err := child.toCheckpointFile(from, to, m)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\n\t\tif val != nil {\n\t\t\tretval.Children[name] = val\n\t\t}\n\t}\n\n\tif len(retval.Children) == 0 && len(retval.Metrics) == 0 {\n\t\treturn nil, nil\n\t}\n\n\treturn retval, nil\n}\n\n// toCheckpoint writes a Level's data to a JSON checkpoint file.\n// Creates directory if needed. Returns ErrNoNewArchiveData if nothing to save.\nfunc (l *Level) toCheckpoint(dir string, from, to int64, m *MemoryStore) error {\n\tcf, err := l.toCheckpointFile(from, to, m)\n\tif err != nil {\n\t\treturn err\n\t}\n\n\tif cf == nil {\n\t\treturn ErrNoNewArchiveData\n\t}\n\n\tfilepath := path.Join(dir, fmt.Sprintf(\"%d.json\", from))\n\tf, err := os.OpenFile(filepath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n\tif err != nil && os.IsNotExist(err) {\n\t\terr = os.MkdirAll(dir, CheckpointDirPerms)\n\t\tif err == nil {\n\t\t\tf, err = os.OpenFile(filepath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n\t\t}\n\t}\n\tif err != nil {\n\t\treturn err\n\t}\n\tdefer f.Close()\n\n\tbw := bufio.NewWriter(f)\n\tif err = json.NewEncoder(bw).Encode(cf); err != nil {\n\t\treturn err\n\t}\n\n\treturn bw.Flush()\n}\n\n// enqueueCheckpointHosts traverses checkpoint directory and enqueues cluster/host pairs.\n// Returns error if directory structure is invalid.\nfunc enqueueCheckpointHosts(dir string, work chan<- [2]string) error {\n\tclustersDir, err := os.ReadDir(dir)\n\tif err != nil {\n\t\treturn err\n\t}\n\n\tfor _, clusterDir := range clustersDir {\n\t\tif !clusterDir.IsDir() {\n\t\t\treturn errors.New(\"[METRICSTORE]> expected only directories at first level of checkpoints/ directory\")\n\t\t}\n\n\t\thostsDir, err := os.ReadDir(filepath.Join(dir, clusterDir.Name()))\n\t\tif err != nil {\n\t\t\treturn err\n\t\t}\n\n\t\tfor _, hostDir := range hostsDir {\n\t\t\tif !hostDir.IsDir() {\n\t\t\t\treturn errors.New(\"[METRICSTORE]> expected only directories at second level of checkpoints/ directory\")\n\t\t\t}\n\n\t\t\twork <- [2]string{clusterDir.Name(), hostDir.Name()}\n\t\t}\n\t}\n\n\treturn nil\n}\n\n// FromCheckpoint loads checkpoint files from disk into memory in parallel.\n//\n// Uses worker pool to load cluster/host combinations. Returns number of files\n// loaded and any errors.\nfunc (m *MemoryStore) FromCheckpoint(dir string, from int64) (int, error) {\n\tvar wg sync.WaitGroup\n\twork := make(chan [2]string, Keys.NumWorkers*4)\n\tn, errs := int32(0), int32(0)\n\n\twg.Add(Keys.NumWorkers)\n\tfor worker := 0; worker < Keys.NumWorkers; worker++ {\n\t\tgo func() {\n\t\t\tdefer wg.Done()\n\t\t\tfor host := range work {\n\t\t\t\tlvl := m.root.findLevelOrCreate(host[:], len(m.Metrics))\n\t\t\t\tnn, err := lvl.fromCheckpoint(m, filepath.Join(dir, host[0], host[1]), from)\n\t\t\t\tif err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> error while loading checkpoints for %s/%s: %s\", host[0], host[1], err.Error())\n\t\t\t\t\tatomic.AddInt32(&errs, 1)\n\t\t\t\t}\n\t\t\t\tatomic.AddInt32(&n, int32(nn))\n\t\t\t}\n\t\t}()\n\t}\n\n\terr := enqueueCheckpointHosts(dir, work)\n\tclose(work)\n\twg.Wait()\n\n\tif err != nil {\n\t\treturn int(n), err\n\t}\n\n\tif errs > 0 {\n\t\treturn int(n), fmt.Errorf(\"[METRICSTORE]> %d errors happened while creating checkpoints (%d successes)\", errs, n)\n\t}\n\treturn int(n), nil\n}\n\n// FromCheckpointFiles is the main entry point for loading checkpoints at startup.\n//\n// Creates checkpoint directory if it doesn't exist. This function must be called\n// before any writes or reads, and can only be called once.\nfunc (m *MemoryStore) FromCheckpointFiles(dir string, from int64) (int, error) {\n\tif _, err := os.Stat(dir); os.IsNotExist(err) {\n\t\terr := os.MkdirAll(dir, CheckpointDirPerms)\n\t\tif err != nil {\n\t\t\tcclog.Fatalf(\"[METRICSTORE]> Error creating directory: %#v\\n\", err)\n\t\t}\n\t\tcclog.Debugf(\"[METRICSTORE]> %#v Directory created successfully\", dir)\n\t}\n\n\treturn m.FromCheckpoint(dir, from)\n}\n\nfunc (l *Level) loadJSONFile(m *MemoryStore, f *os.File, from int64) error {\n\tbr := bufio.NewReader(f)\n\tcf := &CheckpointFile{}\n\tif err := json.NewDecoder(br).Decode(cf); err != nil {\n\t\treturn err\n\t}\n\n\tif cf.To != 0 && cf.To < from {\n\t\treturn nil\n\t}\n\n\tif err := l.loadFile(cf, m); err != nil {\n\t\treturn err\n\t}\n\n\treturn nil\n}\n\nfunc (l *Level) loadFile(cf *CheckpointFile, m *MemoryStore) error {\n\tfor name, metric := range cf.Metrics {\n\t\tn := len(metric.Data)\n\t\tb := &buffer{\n\t\t\tfrequency: metric.Frequency,\n\t\t\tstart: metric.Start,\n\t\t\tdata: metric.Data[0:n:n],\n\t\t\tprev: nil,\n\t\t\tnext: nil,\n\t\t\tarchived: true,\n\t\t}\n\n\t\tminfo, ok := m.Metrics[name]\n\t\tif !ok {\n\t\t\tcontinue\n\t\t}\n\n\t\tprev := l.metrics[minfo.offset]\n\t\tif prev == nil {\n\t\t\tl.metrics[minfo.offset] = b\n\t\t} else {\n\t\t\tif prev.start > b.start {\n\t\t\t\treturn fmt.Errorf(\"[METRICSTORE]> buffer start time %d is before previous buffer start %d\", b.start, prev.start)\n\t\t\t}\n\n\t\t\tb.prev = prev\n\t\t\tprev.next = b\n\t\t}\n\t\tl.metrics[minfo.offset] = b\n\t}\n\n\tif len(cf.Children) > 0 && l.children == nil {\n\t\tl.children = make(map[string]*Level)\n\t}\n\n\tfor sel, childCf := range cf.Children {\n\t\tchild, ok := l.children[sel]\n\t\tif !ok {\n\t\t\tchild = &Level{\n\t\t\t\tmetrics: make([]*buffer, len(m.Metrics)),\n\t\t\t\tchildren: nil,\n\t\t\t}\n\t\t\tl.children[sel] = child\n\t\t}\n\n\t\tif err := child.loadFile(childCf, m); err != nil {\n\t\t\treturn err\n\t\t}\n\t}\n\n\treturn nil\n}\n\n// fromCheckpoint loads all checkpoint files (JSON, binary snapshot, WAL) for a\n// single host directory. Snapshot files are loaded first (sorted by timestamp),\n// then current.wal is replayed on top.\nfunc (l *Level) fromCheckpoint(m *MemoryStore, dir string, from int64) (int, error) {\n\tdirentries, err := os.ReadDir(dir)\n\tif err != nil {\n\t\tif os.IsNotExist(err) {\n\t\t\treturn 0, nil\n\t\t}\n\t\treturn 0, err\n\t}\n\n\tallFiles := make([]fs.DirEntry, 0)\n\tvar walEntry fs.DirEntry\n\tfilesLoaded := 0\n\n\tfor _, e := range direntries {\n\t\tif e.IsDir() {\n\t\t\t// Legacy: skip subdirectories (only used by old Avro format).\n\t\t\t// These are ignored; their data is not loaded.\n\t\t\tcclog.Debugf(\"[METRICSTORE]> skipping subdirectory %s in checkpoint dir %s\", e.Name(), dir)\n\t\t\tcontinue\n\t\t}\n\n\t\tname := e.Name()\n\t\tif strings.HasSuffix(name, \".json\") || strings.HasSuffix(name, \".bin\") {\n\t\t\tallFiles = append(allFiles, e)\n\t\t} else if name == \"current.wal\" {\n\t\t\twalEntry = e\n\t\t}\n\t\t// Silently ignore other files (e.g., .tmp, .bin.tmp from interrupted writes).\n\t}\n\n\tfiles, err := findFiles(allFiles, from, true)\n\tif err != nil {\n\t\treturn filesLoaded, err\n\t}\n\n\tloaders := map[string]func(*MemoryStore, *os.File, int64) error{\n\t\t\".json\": l.loadJSONFile,\n\t\t\".bin\": l.loadBinaryFile,\n\t}\n\n\tfor _, filename := range files {\n\t\text := filepath.Ext(filename)\n\t\tloader := loaders[ext]\n\t\tif loader == nil {\n\t\t\tcclog.Warnf(\"[METRICSTORE]> unknown extension for checkpoint file %s\", filename)\n\t\t\tcontinue\n\t\t}\n\n\t\terr := func() error {\n\t\t\tf, err := os.Open(path.Join(dir, filename))\n\t\t\tif err != nil {\n\t\t\t\treturn err\n\t\t\t}\n\t\t\tdefer f.Close()\n\t\t\treturn loader(m, f, from)\n\t\t}()\n\t\tif err != nil {\n\t\t\treturn filesLoaded, err\n\t\t}\n\t\tfilesLoaded++\n\t}\n\n\t// Replay WAL after all snapshot files so it fills in data since the last snapshot.\n\tif walEntry != nil {\n\t\terr := func() error {\n\t\t\tf, err := os.Open(path.Join(dir, walEntry.Name()))\n\t\t\tif err != nil {\n\t\t\t\treturn err\n\t\t\t}\n\t\t\tdefer f.Close()\n\t\t\treturn l.loadWALFile(m, f, from)\n\t\t}()\n\t\tif err != nil {\n\t\t\t// WAL errors are non-fatal: the snapshot already loaded the bulk of data.\n\t\t\tcclog.Warnf(\"[METRICSTORE]> WAL replay error for %s: %v (data since last snapshot may be missing)\", dir, err)\n\t\t} else {\n\t\t\tfilesLoaded++\n\t\t}\n\t}\n\n\treturn filesLoaded, nil\n}\n\n// parseTimestampFromFilename extracts a Unix timestamp from a checkpoint filename.\n// Supports \".json\" (format: \".json\") and \".bin\" (format: \".bin\").\nfunc parseTimestampFromFilename(name string) (int64, error) {\n\tswitch {\n\tcase strings.HasSuffix(name, \".json\"):\n\t\treturn strconv.ParseInt(name[:len(name)-5], 10, 64)\n\tcase strings.HasSuffix(name, \".bin\"):\n\t\treturn strconv.ParseInt(name[:len(name)-4], 10, 64)\n\tdefault:\n\t\treturn 0, fmt.Errorf(\"unknown checkpoint extension for file %q\", name)\n\t}\n}\n\n// findFiles returns filenames from direntries whose timestamps satisfy the filter.\n// If findMoreRecentFiles is true, returns files with timestamps >= t (plus the\n// last file before t if t falls between two files).\nfunc findFiles(direntries []fs.DirEntry, t int64, findMoreRecentFiles bool) ([]string, error) {\n\tnums := map[string]int64{}\n\tfor _, e := range direntries {\n\t\tname := e.Name()\n\t\tif !strings.HasSuffix(name, \".json\") && !strings.HasSuffix(name, \".bin\") {\n\t\t\tcontinue\n\t\t}\n\n\t\tts, err := parseTimestampFromFilename(name)\n\t\tif err != nil {\n\t\t\treturn nil, err\n\t\t}\n\t\tnums[name] = ts\n\t}\n\n\tsort.Slice(direntries, func(i, j int) bool {\n\t\ta, b := direntries[i], direntries[j]\n\t\treturn nums[a.Name()] < nums[b.Name()]\n\t})\n\n\tif len(nums) == 0 {\n\t\treturn nil, nil\n\t}\n\n\tfilenames := make([]string, 0)\n\n\tfor i, e := range direntries {\n\t\tts1 := nums[e.Name()]\n\n\t\tif findMoreRecentFiles && t <= ts1 {\n\t\t\tfilenames = append(filenames, e.Name())\n\t\t} else if !findMoreRecentFiles && ts1 <= t && ts1 != 0 {\n\t\t\tfilenames = append(filenames, e.Name())\n\t\t}\n\n\t\tif i == len(direntries)-1 {\n\t\t\tcontinue\n\t\t}\n\n\t\tenext := direntries[i+1]\n\t\tts2 := nums[enext.Name()]\n\n\t\tif findMoreRecentFiles {\n\t\t\tif ts1 < t && t < ts2 {\n\t\t\t\tfilenames = append(filenames, e.Name())\n\t\t\t}\n\t\t}\n\t}\n\n\treturn filenames, nil\n}\n","structuredPatch":[{"oldStart":126,"oldLines":6,"newStart":126,"newLines":10,"lines":[" cclog.Infof(\"[METRICSTORE]> start checkpointing (starting at %s)...\", from.Format(time.RFC3339))"," "," if Keys.Checkpoints.FileFormat == \"wal\" {","+ // Pause WAL writes: the binary snapshot captures all in-memory","+ // data, so WAL records written during checkpoint are redundant","+ // and would be deleted during rotation anyway.","+ walCheckpointActive.Store(true)"," n, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())"," if err != nil {"," cclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())"]},{"oldStart":138,"oldLines":6,"newStart":142,"newLines":8,"lines":[" // Rotate WAL files for successfully checkpointed hosts."," RotateWALFiles(hostDirs)"," }","+ walCheckpointActive.Store(false)","+ walDropped.Store(0)"," } else {"," n, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())"," if err != nil {"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"aefa9947-e1a5-49b4-863b-635d5ddddf1b","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"3ca732bc-2a47-4f50-99dc-315f4027209e","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01H7wAFnvLZaih42BxD2a8jV","type":"message","role":"assistant","content":[{"type":"text","text":"Now let me verify it compiles and tests pass."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":644,"cache_read_input_tokens":54430,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":644},"output_tokens":1,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7Z2XHKRUqXpB5cGFoP","type":"assistant","uuid":"d4590c72-ef4c-4ebf-9105-8d97051715ff","timestamp":"2026-03-29T09:12:29.191Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"d4590c72-ef4c-4ebf-9105-8d97051715ff","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01H7wAFnvLZaih42BxD2a8jV","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01Ltug8oMfUA2jUZWEDdYf8r","name":"Bash","input":{"command":"go build ./...","description":"Build all 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{"parentUuid":"5c5952a4-4318-446a-bb5e-1b88cdc7fbb0","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01Ltug8oMfUA2jUZWEDdYf8r","type":"tool_result","content":"(Bash completed with no output)","is_error":false}]},"uuid":"4316b231-0780-46e3-90a0-4db7e4bb019f","timestamp":"2026-03-29T09:12:36.076Z","toolUseResult":{"stdout":"","stderr":"","interrupted":false,"isImage":false,"noOutputExpected":false},"sourceToolAssistantUUID":"5c5952a4-4318-446a-bb5e-1b88cdc7fbb0","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"4316b231-0780-46e3-90a0-4db7e4bb019f","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01C9MAcBiv4DyQdT9MsScs4V","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01ARcUZKRrPuPZsbUfJQTc23","name":"Bash","input":{"command":"go test ./pkg/metricstore/...","description":"Run metricstore tests","timeout":120000},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":121,"cache_read_input_tokens":55074,"output_tokens":99,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":121,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7ZtmEafTspyZR3HDJM","type":"assistant","uuid":"a6105950-1acc-4fb1-a22c-cb8aa1493d32","timestamp":"2026-03-29T09:12:39.315Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"a6105950-1acc-4fb1-a22c-cb8aa1493d32","isSidechain":false,"promptId":"622c9ce6-e9ff-41e6-a17a-6dded67fef23","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01ARcUZKRrPuPZsbUfJQTc23","type":"tool_result","content":"ok \tgithub.com/ClusterCockpit/cc-backend/pkg/metricstore\t0.464s","is_error":false}]},"uuid":"15e40b8e-879e-4469-996f-fef935a0807f","timestamp":"2026-03-29T09:12:40.841Z","toolUseResult":{"stdout":"ok \tgithub.com/ClusterCockpit/cc-backend/pkg/metricstore\t0.464s","stderr":"","interrupted":false,"isImage":false,"noOutputExpected":false},"sourceToolAssistantUUID":"a6105950-1acc-4fb1-a22c-cb8aa1493d32","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"15e40b8e-879e-4469-996f-fef935a0807f","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_013mTQ13ZZr6pGmMN2BGyjaY","type":"message","role":"assistant","content":[{"type":"text","text":"Builds and tests pass. Here's a summary of the 3 changes:\n\n1. **`walCheckpoint.go`**: Added `walCheckpointActive` atomic flag. `SendWALMessage` returns `true` (not `false`) when the flag is set — no channel pressure, no false drop warnings.\n\n2. **`walCheckpoint.go:ToCheckpointWAL`**: Removed the direct `os.Remove(walPath)` inside checkpoint workers (lines 730-733). This raced with the WAL staging goroutine that still had the file open. `RotateWALFiles` already handles deletion properly through the staging goroutine.\n\n3. **`checkpoint.go`**: Set `walCheckpointActive` before `ToCheckpointWAL`, clear it after rotation completes. Reset `walDropped` counter. The flag is always cleared even if checkpoint errors occur."}],"stop_reason":"end_turn","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":138,"cache_read_input_tokens":55195,"output_tokens":209,"server_tool_use":{"web_search_requests":0,"web_fetch_requests":0},"service_tier":"standard","cache_creation":{"ephemeral_1h_input_tokens":138,"ephemeral_5m_input_tokens":0},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CZX7aF76gPiUm6BDL46Pi","type":"assistant","uuid":"44991b9d-bfaa-448b-becb-74b8c42bb5e1","timestamp":"2026-03-29T09:12:47.137Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"44991b9d-bfaa-448b-becb-74b8c42bb5e1","isSidechain":false,"type":"system","subtype":"stop_hook_summary","hookCount":1,"hookInfos":[{"command":"entire hooks claude-code stop","durationMs":3496}],"hookErrors":[],"preventedContinuation":false,"stopReason":"","hasOutput":false,"level":"suggestion","timestamp":"2026-03-29T09:12:50.654Z","uuid":"901eaaac-ca5b-4382-8575-b709164db9d6","toolUseID":"e5bcfa81-1a30-4b22-9974-6a2bd272e0b9","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"901eaaac-ca5b-4382-8575-b709164db9d6","isSidechain":false,"type":"system","subtype":"turn_duration","durationMs":405438,"messageCount":68,"timestamp":"2026-03-29T09:12:50.654Z","uuid":"593c9903-d580-4209-8131-e9fcf06e8920","isMeta":false,"userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"593c9903-d580-4209-8131-e9fcf06e8920","isSidechain":false,"promptId":"ceeea3cc-a7aa-4e59-a96c-f057fd037eac","type":"user","message":{"role":"user","content":"Commit it"},"uuid":"a96c3af9-31de-4dd8-960f-60bbe3cf4ec0","timestamp":"2026-03-29T09:13:28.214Z","permissionMode":"acceptEdits","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"type":"file-history-snapshot","messageId":"a96c3af9-31de-4dd8-960f-60bbe3cf4ec0","snapshot":{"messageId":"a96c3af9-31de-4dd8-960f-60bbe3cf4ec0","trackedFileBackups":{"/Users/jan/.claude/plans/lovely-soaring-snail.md":{"backupFileName":"2e133cf7f5056988@v2","version":2,"backupTime":"2026-03-29T09:13:28.737Z"},"pkg/metricstore/checkpoint.go":{"backupFileName":"6cd2cc2f9fa35484@v2","version":2,"backupTime":"2026-03-29T09:13:28.738Z"},"pkg/metricstore/walCheckpoint.go":{"backupFileName":"f5b5b4bac0274f50@v2","version":2,"backupTime":"2026-03-29T09:13:28.738Z"}},"timestamp":"2026-03-29T09:13:28.738Z"},"isSnapshotUpdate":false} {"parentUuid":"a96c3af9-31de-4dd8-960f-60bbe3cf4ec0","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_017bvnsT2sBuKGgPyQ6rHzum","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_013bFJvcQRAJuabmyZSzBkjA","name":"Bash","input":{"command":"git status","description":"Show working tree status"},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":276,"cache_read_input_tokens":55333,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":276},"output_tokens":67,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CZX7dmnuAgbUVri5A87ec","type":"assistant","uuid":"63ecb81f-48a6-49dd-94a0-a301940f6e94","timestamp":"2026-03-29T09:13:32.682Z","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"63ecb81f-48a6-49dd-94a0-a301940f6e94","isSidechain":false,"promptId":"ceeea3cc-a7aa-4e59-a96c-f057fd037eac","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_013bFJvcQRAJuabmyZSzBkjA","type":"tool_result","content":"On branch hotfix\nYour branch is up to date with 'origin/hotfix'.\n\nChanges not staged for commit:\n (use \"git add ...\" to update what will be committed)\n (use \"git restore ...\" to discard changes in working directory)\n\tmodified: pkg/metricstore/checkpoint.go\n\tmodified: pkg/metricstore/walCheckpoint.go\n\nno changes added to commit (use \"git add\" and/or \"git commit -a\")","is_error":false}]},"uuid":"24e3f10a-3f3a-4c98-988e-3040b757691b","timestamp":"2026-03-29T09:13:32.736Z","toolUseResult":{"stdout":"On branch hotfix\nYour branch is up to date with 'origin/hotfix'.\n\nChanges not staged for commit:\n (use \"git add ...\" to update what will be committed)\n (use \"git restore ...\" to discard changes in working directory)\n\tmodified: pkg/metricstore/checkpoint.go\n\tmodified: pkg/metricstore/walCheckpoint.go\n\nno changes added to commit (use \"git add\" and/or \"git commit 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b/pkg/metricstore/checkpoint.go\nindex 2dcb5733..d408ce72 100644\n--- a/pkg/metricstore/checkpoint.go\n+++ b/pkg/metricstore/checkpoint.go\n@@ -126,6 +126,10 @@ func Checkpointing(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\tcclog.Infof(\"[METRICSTORE]> start checkpointing (starting at %s)...\", from.Format(time.RFC3339))\n \n \t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n+\t\t\t\t\t// Pause WAL writes: the binary snapshot captures all in-memory\n+\t\t\t\t\t// data, so WAL records written during checkpoint are redundant\n+\t\t\t\t\t// and would be deleted during rotation anyway.\n+\t\t\t\t\twalCheckpointActive.Store(true)\n \t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n \t\t\t\t\tif err != nil {\n \t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n@@ -138,6 +142,8 @@ func Checkpointing(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n \t\t\t\t\t\tRotateWALFiles(hostDirs)\n \t\t\t\t\t}\n+\t\t\t\t\twalCheckpointActive.Store(false)\n+\t\t\t\t\twalDropped.Store(0)\n \t\t\t\t} else {\n \t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n \t\t\t\t\tif err != nil {\ndiff --git a/pkg/metricstore/walCheckpoint.go b/pkg/metricstore/walCheckpoint.go\nindex 749ff756..0d0b2c8e 100644\n--- a/pkg/metricstore/walCheckpoint.go\n+++ b/pkg/metricstore/walCheckpoint.go\n@@ -99,6 +99,11 @@ var walStagingWg sync.WaitGroup\n // SendWALMessage from sending on a closed channel (which panics in Go).\n var walShuttingDown atomic.Bool\n \n+// walCheckpointActive is set during binary checkpoint writes.\n+// While active, SendWALMessage skips sending (returns true) because the\n+// snapshot captures all in-memory data, making WAL writes redundant.\n+var walCheckpointActive atomic.Bool\n+\n // WALMessage represents a single metric write to be appended to the WAL.\n // Cluster and Node are NOT stored in the WAL record (inferred from file path).\n type WALMessage struct {\n@@ -146,6 +151,9 @@ func SendWALMessage(msg *WALMessage) bool {\n \tif walShardChs == nil || walShuttingDown.Load() {\n \t\treturn false\n \t}\n+\tif walCheckpointActive.Load() {\n+\t\treturn true // Data safe in memory; snapshot will capture it\n+\t}\n \tshard := walShardIndex(msg.Cluster, msg.Node)\n \tselect {\n \tcase walShardChs[shard] <- msg:\n@@ -727,11 +735,6 @@ func (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string\n \t\t\t\t\tatomic.AddInt32(&errs, 1)\n \t\t\t\t} else {\n \t\t\t\t\tatomic.AddInt32(&n, 1)\n-\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n-\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n-\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n-\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n-\t\t\t\t\t}\n \t\t\t\t\tsuccessMu.Lock()\n \t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n \t\t\t\t\tsuccessMu.Unlock()","is_error":false}]},"uuid":"db658a0e-fe1c-4bcc-86e9-52ec52afc3c1","timestamp":"2026-03-29T09:13:33.344Z","toolUseResult":{"stdout":"diff --git a/pkg/metricstore/checkpoint.go b/pkg/metricstore/checkpoint.go\nindex 2dcb5733..d408ce72 100644\n--- a/pkg/metricstore/checkpoint.go\n+++ b/pkg/metricstore/checkpoint.go\n@@ -126,6 +126,10 @@ func Checkpointing(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\tcclog.Infof(\"[METRICSTORE]> start checkpointing (starting at %s)...\", from.Format(time.RFC3339))\n \n \t\t\t\tif Keys.Checkpoints.FileFormat == \"wal\" {\n+\t\t\t\t\t// Pause WAL writes: the binary snapshot captures all in-memory\n+\t\t\t\t\t// data, so WAL records written during checkpoint are redundant\n+\t\t\t\t\t// and would be deleted during rotation anyway.\n+\t\t\t\t\twalCheckpointActive.Store(true)\n \t\t\t\t\tn, hostDirs, err := ms.ToCheckpointWAL(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n \t\t\t\t\tif err != nil {\n \t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpointing failed: %s\", err.Error())\n@@ -138,6 +142,8 @@ func Checkpointing(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\t\t\t// Rotate WAL files for successfully checkpointed hosts.\n \t\t\t\t\t\tRotateWALFiles(hostDirs)\n \t\t\t\t\t}\n+\t\t\t\t\twalCheckpointActive.Store(false)\n+\t\t\t\t\twalDropped.Store(0)\n \t\t\t\t} else {\n \t\t\t\t\tn, err := ms.ToCheckpoint(Keys.Checkpoints.RootDir, from.Unix(), now.Unix())\n \t\t\t\t\tif err != nil {\ndiff --git a/pkg/metricstore/walCheckpoint.go b/pkg/metricstore/walCheckpoint.go\nindex 749ff756..0d0b2c8e 100644\n--- a/pkg/metricstore/walCheckpoint.go\n+++ b/pkg/metricstore/walCheckpoint.go\n@@ -99,6 +99,11 @@ var walStagingWg sync.WaitGroup\n // SendWALMessage from sending on a closed channel (which panics in Go).\n var walShuttingDown atomic.Bool\n \n+// walCheckpointActive is set during binary checkpoint writes.\n+// While active, SendWALMessage skips sending (returns true) because the\n+// snapshot captures all in-memory data, making WAL writes redundant.\n+var walCheckpointActive atomic.Bool\n+\n // WALMessage represents a single metric write to be appended to the WAL.\n // Cluster and Node are NOT stored in the WAL record (inferred from file path).\n type WALMessage struct {\n@@ -146,6 +151,9 @@ func SendWALMessage(msg *WALMessage) bool {\n \tif walShardChs == nil || walShuttingDown.Load() {\n \t\treturn false\n \t}\n+\tif walCheckpointActive.Load() {\n+\t\treturn true // Data safe in memory; snapshot will capture it\n+\t}\n \tshard := walShardIndex(msg.Cluster, msg.Node)\n \tselect {\n \tcase walShardChs[shard] <- msg:\n@@ -727,11 +735,6 @@ func (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string\n \t\t\t\t\tatomic.AddInt32(&errs, 1)\n \t\t\t\t} else {\n \t\t\t\t\tatomic.AddInt32(&n, 1)\n-\t\t\t\t\t// Delete WAL immediately after successful snapshot.\n-\t\t\t\t\twalPath := path.Join(wi.hostDir, \"current.wal\")\n-\t\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n-\t\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL remove %s: %v\", walPath, err)\n-\t\t\t\t\t}\n \t\t\t\t\tsuccessMu.Lock()\n \t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n \t\t\t\t\tsuccessMu.Unlock()","stderr":"","interrupted":false,"isImage":false,"noOutputExpected":false},"sourceToolAssistantUUID":"a405089c-785f-4662-b1dc-5b344eeb0960","userType":"external","entrypoint":"cli","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"76beb79f-6bc7-43c0-a87a-612aba368c74","version":"2.1.87","gitBranch":"hotfix","slug":"lovely-soaring-snail"} {"parentUuid":"db658a0e-fe1c-4bcc-86e9-52ec52afc3c1","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_017bvnsT2sBuKGgPyQ6rHzum","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01Wn6BkkFqQPw7FoFsZXL2UE","name":"Bash","input":{"command":"git log --oneline -5","description":"Show recent 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