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cc-backend/c1/1d1a65fae4/0/full.jsonl
Jan Eitzinger f2b76c3fac Checkpoint: c11d1a65fae4 
Entire-Session: 26ab707c-a69c-4886-8226-dfb24388d9b4
Entire-Strategy: manual-commit
Entire-Agent: Claude Code
Ephemeral-branch: entire/b214e17-e3b0c4
2026-03-13 09:07:39 +01:00

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{"parentUuid":"cafe66fe-66e0-4f5d-be56-934a78d9ffdb","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":"Implement the following plan:\n\n# Remaining Improvements for Metricstore\n\n## IMPROVEMENT 1: WAL buffering — RECOMMEND\n- `walFileState` (walCheckpoint.go:110) currently holds only `f *os.File`\n- Each `writeWALRecord` call (line 307) does a raw `f.Write()` syscall\n- Add `w *bufio.Writer` to `walFileState`, wrap `f` on creation (line 163)\n- `writeWALRecord` writes to `bufio.Writer` instead of `*os.File`\n- Flush in `processRotate` (line 178) before Close\n- Flush in defer cleanup (line 126) before Close\n- Flush in `drain()` (line 191) after processing remaining messages\n\n## IMPROVEMENT 3: MemoryCap comment fix — RECOMMEND (trivial)\n- `config.go:116` comment says \"Max bytes\" but code treats it as GB\n- Fix comment to say \"Max memory in GB\"\n\n## Files to modify\n- `pkg/metricstore/walCheckpoint.go` — IMP 1: add `bufio.Writer` to `walFileState`, use in `writeWALRecord`, flush on rotate/close/drain\n- `pkg/metricstore/config.go:116` — IMP 3: fix comment \"Max bytes\" → \"Max memory in GB\"\n\n## NOT recommended now\n- **IMP 4 (WAL size limit)**: High complexity, checkpoint-interval (already configurable) is the simpler lever\n- **Bug 5 (periodic fsync)**: CRC handles corrupt trailing records; WAL is best-effort on top of snapshots\n\n## Verification\n```bash\ngo test ./pkg/metricstore/...\n```\n\n\nIf you need specific details from before exiting plan mode (like exact code snippets, error messages, or content you generated), read the full transcript at: /Users/jan/.claude/projects/-Users-jan-prg-ClusterCockpit-cc-backend/f12048ec-dcf9-4d07-a9c1-0916c9882538.jsonl"},"uuid":"22fbd7ee-87ac-4ddd-b513-e085d3cd54e4","timestamp":"2026-03-13T08:03:08.332Z","planContent":"# Remaining Improvements for Metricstore\n\n## IMPROVEMENT 1: WAL buffering — RECOMMEND\n- `walFileState` (walCheckpoint.go:110) currently holds only `f *os.File`\n- Each `writeWALRecord` call (line 307) does a raw `f.Write()` syscall\n- Add `w *bufio.Writer` to `walFileState`, wrap `f` on creation (line 163)\n- `writeWALRecord` writes to `bufio.Writer` instead of `*os.File`\n- Flush in `processRotate` (line 178) before Close\n- Flush in defer cleanup (line 126) before Close\n- Flush in `drain()` (line 191) after processing remaining messages\n\n## IMPROVEMENT 3: MemoryCap comment fix — RECOMMEND (trivial)\n- `config.go:116` comment says \"Max bytes\" but code treats it as GB\n- Fix comment to say \"Max memory in GB\"\n\n## Files to modify\n- `pkg/metricstore/walCheckpoint.go` — IMP 1: add `bufio.Writer` to `walFileState`, use in `writeWALRecord`, flush on rotate/close/drain\n- `pkg/metricstore/config.go:116` — IMP 3: fix comment \"Max bytes\" → \"Max memory in GB\"\n\n## NOT recommended now\n- **IMP 4 (WAL size limit)**: High complexity, checkpoint-interval (already configurable) is the simpler lever\n- **Bug 5 (periodic fsync)**: CRC handles corrupt trailing records; WAL is best-effort on top of snapshots\n\n## Verification\n```bash\ngo test ./pkg/metricstore/...\n```\n","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"cde1dce7-08e3-41fa-a1d4-de5510c3f1dc","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_012N5EPRZueRCJian6TZ74W4","type":"tool_result","content":" 1→// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.\n 2→// All rights reserved. This file is part of cc-backend.\n 3→// Use of this source code is governed by a MIT-style\n 4→// license that can be found in the LICENSE file.\n 5→\n 6→// Package metricstore provides walCheckpoint.go: WAL-based checkpoint implementation.\n 7→//\n 8→// This replaces the Avro shadow tree with an append-only Write-Ahead Log (WAL)\n 9→// per host, eliminating the extra memory overhead of the AvroStore and providing\n 10→// truly continuous (per-write) crash safety.\n 11→//\n 12→// # Architecture\n 13→//\n 14→//\tMetric write (DecodeLine)\n 15→//\t │\n 16→//\t ├─► WriteToLevel() → main MemoryStore (unchanged)\n 17→//\t │\n 18→//\t └─► WALMessages channel\n 19→//\t │\n 20→//\t ▼\n 21→//\t WALStaging goroutine\n 22→//\t │\n 23→//\t ▼\n 24→//\t checkpoints/cluster/host/current.wal (append-only, binary)\n 25→//\n 26→//\tPeriodic checkpoint (Checkpointing goroutine):\n 27→//\t 1. Write <timestamp>.bin snapshot (column-oriented, from main tree)\n 28→//\t 2. Signal WALStaging to truncate current.wal per host\n 29→//\n 30→//\tOn restart (FromCheckpoint):\n 31→//\t 1. Load most recent <timestamp>.bin snapshot\n 32→//\t 2. Replay current.wal (overwrite-safe: buffer.write handles duplicate timestamps)\n 33→//\n 34→// # WAL Record Format\n 35→//\n 36→//\t[4B magic 0xCC1DA7A1][4B payload_len][payload][4B CRC32]\n 37→//\n 38→//\tpayload:\n 39→//\t [8B timestamp int64]\n 40→//\t [2B metric_name_len uint16][N metric name bytes]\n 41→//\t [1B selector_count uint8]\n 42→//\t per selector: [1B selector_len uint8][M selector bytes]\n 43→//\t [4B value float32 bits]\n 44→//\n 45→// # Binary Snapshot Format\n 46→//\n 47→//\t[4B magic 0xCC5B0001][8B from int64][8B to int64]\n 48→//\tLevel tree (recursive):\n 49→//\t [4B num_metrics uint32]\n 50→//\t per metric:\n 51→//\t [2B name_len uint16][N name bytes]\n 52→//\t [8B frequency int64][8B start int64]\n 53→//\t [4B num_values uint32][num_values × 4B float32]\n 54→//\t [4B num_children uint32]\n 55→//\t per child: [2B name_len uint16][N name bytes] + Level (recursive)\n 56→package metricstore\n 57→\n 58→import (\n 59→\t\"bufio\"\n 60→\t\"context\"\n 61→\t\"encoding/binary\"\n 62→\t\"fmt\"\n 63→\t\"hash/crc32\"\n 64→\t\"io\"\n 65→\t\"math\"\n 66→\t\"os\"\n 67→\t\"path\"\n 68→\t\"strings\"\n 69→\t\"sync\"\n 70→\t\"sync/atomic\"\n 71→\n 72→\tcclog \"github.com/ClusterCockpit/cc-lib/v2/ccLogger\"\n 73→\t\"github.com/ClusterCockpit/cc-lib/v2/schema\"\n 74→)\n 75→\n 76→// Magic numbers for binary formats.\n 77→const (\n 78→\twalFileMagic = uint32(0xCC1DA701) // WAL file header magic\n 79→\twalRecordMagic = uint32(0xCC1DA7A1) // WAL record magic\n 80→\tsnapFileMagic = uint32(0xCC5B0001) // Binary snapshot magic\n 81→)\n 82→\n 83→// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n 84→// Buffered to allow burst writes without blocking the metric ingestion path.\n 85→var WALMessages = make(chan *WALMessage, 4096)\n 86→\n 87→// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n 88→// (close, delete, reopen) after a binary snapshot has been written.\n 89→var walRotateCh = make(chan walRotateReq, 256)\n 90→\n 91→// WALMessage represents a single metric write to be appended to the WAL.\n 92→// Cluster and Node are NOT stored in the WAL record (inferred from file path).\n 93→type WALMessage struct {\n 94→\tMetricName string\n 95→\tCluster string\n 96→\tNode string\n 97→\tSelector []string\n 98→\tValue schema.Float\n 99→\tTimestamp int64\n 100→}\n 101→\n 102→// walRotateReq requests WAL file rotation for a specific host directory.\n 103→// The done channel is closed by the WAL goroutine when rotation is complete.\n 104→type walRotateReq struct {\n 105→\thostDir string\n 106→\tdone chan struct{}\n 107→}\n 108→\n 109→// walFileState holds an open WAL file handle for one host directory.\n 110→type walFileState struct {\n 111→\tf *os.File\n 112→}\n 113→\n 114→// WALStaging starts a background goroutine that receives WALMessage items\n 115→// and appends binary WAL records to per-host current.wal files.\n 116→// Also handles WAL rotation requests from the checkpoint goroutine.\n 117→func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n 118→\twg.Go(func() {\n 119→\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n 120→\t\t\treturn\n 121→\t\t}\n 122→\n 123→\t\thostFiles := make(map[string]*walFileState)\n 124→\n 125→\t\tdefer func() {\n 126→\t\t\tfor _, ws := range hostFiles {\n 127→\t\t\t\tif ws.f != nil {\n 128→\t\t\t\t\tws.f.Close()\n 129→\t\t\t\t}\n 130→\t\t\t}\n 131→\t\t}()\n 132→\n 133→\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n 134→\t\t\tws, ok := hostFiles[hostDir]\n 135→\t\t\tif ok {\n 136→\t\t\t\treturn ws.f\n 137→\t\t\t}\n 138→\n 139→\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n 140→\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n 141→\t\t\t\treturn nil\n 142→\t\t\t}\n 143→\n 144→\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n 145→\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n 146→\t\t\tif err != nil {\n 147→\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n 148→\t\t\t\treturn nil\n 149→\t\t\t}\n 150→\n 151→\t\t\t// Write file header magic if file is new (empty).\n 152→\t\t\tinfo, err := f.Stat()\n 153→\t\t\tif err == nil && info.Size() == 0 {\n 154→\t\t\t\tvar hdr [4]byte\n 155→\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n 156→\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n 157→\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n 158→\t\t\t\t\tf.Close()\n 159→\t\t\t\t\treturn nil\n 160→\t\t\t\t}\n 161→\t\t\t}\n 162→\n 163→\t\t\thostFiles[hostDir] = &walFileState{f: f}\n 164→\t\t\treturn f\n 165→\t\t}\n 166→\n 167→\t\tprocessMsg := func(msg *WALMessage) {\n 168→\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n 169→\t\t\tf := getOrOpenWAL(hostDir)\n 170→\t\t\tif f == nil {\n 171→\t\t\t\treturn\n 172→\t\t\t}\n 173→\t\t\tif err := writeWALRecord(f, msg); err != nil {\n 174→\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n 175→\t\t\t}\n 176→\t\t}\n 177→\n 178→\t\tprocessRotate := func(req walRotateReq) {\n 179→\t\t\tws, ok := hostFiles[req.hostDir]\n 180→\t\t\tif ok && ws.f != nil {\n 181→\t\t\t\tws.f.Close()\n 182→\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n 183→\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n 184→\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n 185→\t\t\t\t}\n 186→\t\t\t\tdelete(hostFiles, req.hostDir)\n 187→\t\t\t}\n 188→\t\t\tclose(req.done)\n 189→\t\t}\n 190→\n 191→\t\tdrain := func() {\n 192→\t\t\tfor {\n 193→\t\t\t\tselect {\n 194→\t\t\t\tcase msg, ok := <-WALMessages:\n 195→\t\t\t\t\tif !ok {\n 196→\t\t\t\t\t\treturn\n 197→\t\t\t\t\t}\n 198→\t\t\t\t\tprocessMsg(msg)\n 199→\t\t\t\tcase req := <-walRotateCh:\n 200→\t\t\t\t\tprocessRotate(req)\n 201→\t\t\t\tdefault:\n 202→\t\t\t\t\treturn\n 203→\t\t\t\t}\n 204→\t\t\t}\n 205→\t\t}\n 206→\n 207→\t\tfor {\n 208→\t\t\tselect {\n 209→\t\t\tcase <-ctx.Done():\n 210→\t\t\t\tdrain()\n 211→\t\t\t\treturn\n 212→\t\t\tcase msg, ok := <-WALMessages:\n 213→\t\t\t\tif !ok {\n 214→\t\t\t\t\treturn\n 215→\t\t\t\t}\n 216→\t\t\t\tprocessMsg(msg)\n 217→\t\t\tcase req := <-walRotateCh:\n 218→\t\t\t\tprocessRotate(req)\n 219→\t\t\t}\n 220→\t\t}\n 221→\t})\n 222→}\n 223→\n 224→// RotateWALFiles sends rotation requests for the given host directories\n 225→// and blocks until all rotations complete.\n 226→func RotateWALFiles(hostDirs []string) {\n 227→\tdones := make([]chan struct{}, len(hostDirs))\n 228→\tfor i, dir := range hostDirs {\n 229→\t\tdones[i] = make(chan struct{})\n 230→\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n 231→\t}\n 232→\tfor _, done := range dones {\n 233→\t\t<-done\n 234→\t}\n 235→}\n 236→\n 237→// RotateWALFiles sends rotation requests for the given host directories\n 238→// and blocks until all rotations complete.\n 239→func RotateWALFilesAfterShutdown(hostDirs []string) {\n 240→\tfor _, dir := range hostDirs {\n 241→\t\twalPath := path.Join(dir, \"current.wal\")\n 242→\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n 243→\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n 244→\t\t}\n 245→\t}\n 246→}\n 247→\n 248→// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\n 249→func buildWALPayload(msg *WALMessage) []byte {\n 250→\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n 251→\tfor _, s := range msg.Selector {\n 252→\t\tsize += 1 + len(s)\n 253→\t}\n 254→\n 255→\tbuf := make([]byte, 0, size)\n 256→\n 257→\t// Timestamp (8 bytes, little-endian int64)\n 258→\tvar ts [8]byte\n 259→\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n 260→\tbuf = append(buf, ts[:]...)\n 261→\n 262→\t// Metric name (2-byte length prefix + bytes)\n 263→\tvar mLen [2]byte\n 264→\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n 265→\tbuf = append(buf, mLen[:]...)\n 266→\tbuf = append(buf, msg.MetricName...)\n 267→\n 268→\t// Selector count (1 byte)\n 269→\tbuf = append(buf, byte(len(msg.Selector)))\n 270→\n 271→\t// Selectors (1-byte length prefix + bytes each)\n 272→\tfor _, sel := range msg.Selector {\n 273→\t\tbuf = append(buf, byte(len(sel)))\n 274→\t\tbuf = append(buf, sel...)\n 275→\t}\n 276→\n 277→\t// Value (4 bytes, float32 bit representation)\n 278→\tvar val [4]byte\n 279→\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n 280→\tbuf = append(buf, val[:]...)\n 281→\n 282→\treturn buf\n 283→}\n 284→\n 285→// writeWALRecord appends a binary WAL record to the file.\n 286→// Format: [4B magic][4B payload_len][payload][4B CRC32]\n 287→func writeWALRecord(f *os.File, msg *WALMessage) error {\n 288→\tpayload := buildWALPayload(msg)\n 289→\tcrc := crc32.ChecksumIEEE(payload)\n 290→\n 291→\trecord := make([]byte, 0, 4+4+len(payload)+4)\n 292→\n 293→\tvar magic [4]byte\n 294→\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n 295→\trecord = append(record, magic[:]...)\n 296→\n 297→\tvar pLen [4]byte\n 298→\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n 299→\trecord = append(record, pLen[:]...)\n 300→\n 301→\trecord = append(record, payload...)\n 302→\n 303→\tvar crcBytes [4]byte\n 304→\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n 305→\trecord = append(record, crcBytes[:]...)\n 306→\n 307→\t_, err := f.Write(record)\n 308→\treturn err\n 309→}\n 310→\n 311→// readWALRecord reads one WAL record from the reader.\n 312→// Returns (nil, nil) on clean EOF. Returns error on data corruption.\n 313→// A CRC mismatch indicates a truncated trailing record (expected on crash).\n 314→func readWALRecord(r io.Reader) (*WALMessage, error) {\n 315→\tvar magic uint32\n 316→\tif err := binary.Read(r, binary.LittleEndian, &magic); err != nil {\n 317→\t\tif err == io.EOF {\n 318→\t\t\treturn nil, nil // Clean EOF\n 319→\t\t}\n 320→\t\treturn nil, fmt.Errorf(\"read record magic: %w\", err)\n 321→\t}\n 322→\n 323→\tif magic != walRecordMagic {\n 324→\t\treturn nil, fmt.Errorf(\"invalid record magic 0x%08X (expected 0x%08X)\", magic, walRecordMagic)\n 325→\t}\n 326→\n 327→\tvar payloadLen uint32\n 328→\tif err := binary.Read(r, binary.LittleEndian, &payloadLen); err != nil {\n 329→\t\treturn nil, fmt.Errorf(\"read payload length: %w\", err)\n 330→\t}\n 331→\n 332→\tif payloadLen > 1<<20 { // 1 MB sanity limit\n 333→\t\treturn nil, fmt.Errorf(\"record payload too large: %d bytes\", payloadLen)\n 334→\t}\n 335→\n 336→\tpayload := make([]byte, payloadLen)\n 337→\tif _, err := io.ReadFull(r, payload); err != nil {\n 338→\t\treturn nil, fmt.Errorf(\"read payload: %w\", err)\n 339→\t}\n 340→\n 341→\tvar storedCRC uint32\n 342→\tif err := binary.Read(r, binary.LittleEndian, &storedCRC); err != nil {\n 343→\t\treturn nil, fmt.Errorf(\"read CRC: %w\", err)\n 344→\t}\n 345→\n 346→\tif crc32.ChecksumIEEE(payload) != storedCRC {\n 347→\t\treturn nil, fmt.Errorf(\"CRC mismatch (truncated write or corruption)\")\n 348→\t}\n 349→\n 350→\treturn parseWALPayload(payload)\n 351→}\n 352→\n 353→// parseWALPayload decodes a binary payload into a WALMessage.\n 354→func parseWALPayload(payload []byte) (*WALMessage, error) {\n 355→\tif len(payload) < 8+2+1+4 {\n 356→\t\treturn nil, fmt.Errorf(\"payload too short: %d bytes\", len(payload))\n 357→\t}\n 358→\n 359→\toffset := 0\n 360→\n 361→\t// Timestamp (8 bytes)\n 362→\tts := int64(binary.LittleEndian.Uint64(payload[offset : offset+8]))\n 363→\toffset += 8\n 364→\n 365→\t// Metric name (2-byte length + bytes)\n 366→\tif offset+2 > len(payload) {\n 367→\t\treturn nil, fmt.Errorf(\"metric name length overflows payload\")\n 368→\t}\n 369→\tmLen := int(binary.LittleEndian.Uint16(payload[offset : offset+2]))\n 370→\toffset += 2\n 371→\n 372→\tif offset+mLen > len(payload) {\n 373→\t\treturn nil, fmt.Errorf(\"metric name overflows payload\")\n 374→\t}\n 375→\tmetricName := string(payload[offset : offset+mLen])\n 376→\toffset += mLen\n 377→\n 378→\t// Selector count (1 byte)\n 379→\tif offset >= len(payload) {\n 380→\t\treturn nil, fmt.Errorf(\"selector count overflows payload\")\n 381→\t}\n 382→\tselCount := int(payload[offset])\n 383→\toffset++\n 384→\n 385→\tselectors := make([]string, selCount)\n 386→\tfor i := range selCount {\n 387→\t\tif offset >= len(payload) {\n 388→\t\t\treturn nil, fmt.Errorf(\"selector[%d] length overflows payload\", i)\n 389→\t\t}\n 390→\t\tsLen := int(payload[offset])\n 391→\t\toffset++\n 392→\n 393→\t\tif offset+sLen > len(payload) {\n 394→\t\t\treturn nil, fmt.Errorf(\"selector[%d] data overflows payload\", i)\n 395→\t\t}\n 396→\t\tselectors[i] = string(payload[offset : offset+sLen])\n 397→\t\toffset += sLen\n 398→\t}\n 399→\n 400→\t// Value (4 bytes, float32 bits)\n 401→\tif offset+4 > len(payload) {\n 402→\t\treturn nil, fmt.Errorf(\"value overflows payload\")\n 403→\t}\n 404→\tbits := binary.LittleEndian.Uint32(payload[offset : offset+4])\n 405→\tvalue := schema.Float(math.Float32frombits(bits))\n 406→\n 407→\treturn &WALMessage{\n 408→\t\tMetricName: metricName,\n 409→\t\tTimestamp: ts,\n 410→\t\tSelector: selectors,\n 411→\t\tValue: value,\n 412→\t}, nil\n 413→}\n 414→\n 415→// loadWALFile reads a WAL file and replays all valid records into the Level tree.\n 416→// l is the host-level node. Corrupt or partial trailing records are silently skipped\n 417→// (expected on crash). Records older than 'from' are skipped.\n 418→func (l *Level) loadWALFile(m *MemoryStore, f *os.File, from int64) error {\n 419→\tbr := bufio.NewReader(f)\n 420→\n 421→\t// Verify file header magic.\n 422→\tvar fileMagic uint32\n 423→\tif err := binary.Read(br, binary.LittleEndian, &fileMagic); err != nil {\n 424→\t\tif err == io.EOF {\n 425→\t\t\treturn nil // Empty file, no data\n 426→\t\t}\n 427→\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: read file header: %w\", err)\n 428→\t}\n 429→\n 430→\tif fileMagic != walFileMagic {\n 431→\t\treturn fmt.Errorf(\"[METRICSTORE]> WAL: invalid file magic 0x%08X (expected 0x%08X)\", fileMagic, walFileMagic)\n 432→\t}\n 433→\n 434→\t// Cache level lookups to avoid repeated tree traversal.\n 435→\tlvlCache := make(map[string]*Level)\n 436→\n 437→\tfor {\n 438→\t\tmsg, err := readWALRecord(br)\n 439→\t\tif err != nil {\n 440→\t\t\t// Truncated trailing record is expected after a crash; stop replaying.\n 441→\t\t\tcclog.Debugf(\"[METRICSTORE]> WAL: stopping replay at corrupted/partial record: %v\", err)\n 442→\t\t\tbreak\n 443→\t\t}\n 444→\t\tif msg == nil {\n 445→\t\t\tbreak // Clean EOF\n 446→\t\t}\n 447→\n 448→\t\tif msg.Timestamp < from {\n 449→\t\t\tcontinue // Older than retention window\n 450→\t\t}\n 451→\n 452→\t\tminfo, ok := m.Metrics[msg.MetricName]\n 453→\t\tif !ok {\n 454→\t\t\tcontinue // Unknown metric (config may have changed)\n 455→\t\t}\n 456→\n 457→\t\t// Cache key is the null-separated selector path.\n 458→\t\tcacheKey := joinSelector(msg.Selector)\n 459→\t\tlvl, ok := lvlCache[cacheKey]\n 460→\t\tif !ok {\n 461→\t\t\tlvl = l.findLevelOrCreate(msg.Selector, len(m.Metrics))\n 462→\t\t\tlvlCache[cacheKey] = lvl\n 463→\t\t}\n 464→\n 465→\t\t// Write directly to the buffer, same as WriteToLevel but without the\n 466→\t\t// global level lookup (we already have the right level).\n 467→\t\tlvl.lock.Lock()\n 468→\t\tb := lvl.metrics[minfo.offset]\n 469→\t\tif b == nil {\n 470→\t\t\tb = newBuffer(msg.Timestamp, minfo.Frequency)\n 471→\t\t\tlvl.metrics[minfo.offset] = b\n 472→\t\t}\n 473→\t\tnb, writeErr := b.write(msg.Timestamp, msg.Value)\n 474→\t\tif writeErr == nil && b != nb {\n 475→\t\t\tlvl.metrics[minfo.offset] = nb\n 476→\t\t}\n 477→\t\t// Ignore write errors for timestamps before buffer start (can happen when\n 478→\t\t// replaying WAL entries that predate a loaded snapshot's start time).\n 479→\t\tlvl.lock.Unlock()\n 480→\t}\n 481→\n 482→\treturn nil\n 483→}\n 484→\n 485→// joinSelector builds a cache key from a selector slice using null bytes as separators.\n 486→func joinSelector(sel []string) string {\n 487→\tif len(sel) == 0 {\n 488→\t\treturn \"\"\n 489→\t}\n 490→\tvar result strings.Builder\n 491→\tresult.WriteString(sel[0])\n 492→\tfor i := 1; i < len(sel); i++ {\n 493→\t\tresult.WriteString(\"\\x00\" + sel[i])\n 494→\t}\n 495→\treturn result.String()\n 496→}\n 497→\n 498→// ToCheckpointWAL writes binary snapshot files for all hosts in parallel.\n 499→// Returns the number of files written, the list of host directories that were\n 500→// successfully checkpointed (for WAL rotation), and any errors.\n 501→func (m *MemoryStore) ToCheckpointWAL(dir string, from, to int64) (int, []string, error) {\n 502→\t// Collect all cluster/host pairs.\n 503→\tm.root.lock.RLock()\n 504→\ttotalHosts := 0\n 505→\tfor _, l1 := range m.root.children {\n 506→\t\tl1.lock.RLock()\n 507→\t\ttotalHosts += len(l1.children)\n 508→\t\tl1.lock.RUnlock()\n 509→\t}\n 510→\tm.root.lock.RUnlock()\n 511→\n 512→\tlevels := make([]*Level, 0, totalHosts)\n 513→\tselectors := make([][]string, 0, totalHosts)\n 514→\n 515→\tm.root.lock.RLock()\n 516→\tfor sel1, l1 := range m.root.children {\n 517→\t\tl1.lock.RLock()\n 518→\t\tfor sel2, l2 := range l1.children {\n 519→\t\t\tlevels = append(levels, l2)\n 520→\t\t\tselectors = append(selectors, []string{sel1, sel2})\n 521→\t\t}\n 522→\t\tl1.lock.RUnlock()\n 523→\t}\n 524→\tm.root.lock.RUnlock()\n 525→\n 526→\ttype workItem struct {\n 527→\t\tlevel *Level\n 528→\t\thostDir string\n 529→\t\tselector []string\n 530→\t}\n 531→\n 532→\tn, errs := int32(0), int32(0)\n 533→\tvar successDirs []string\n 534→\tvar successMu sync.Mutex\n 535→\n 536→\tvar wg sync.WaitGroup\n 537→\twg.Add(Keys.NumWorkers)\n 538→\twork := make(chan workItem, Keys.NumWorkers*2)\n 539→\n 540→\tfor range Keys.NumWorkers {\n 541→\t\tgo func() {\n 542→\t\t\tdefer wg.Done()\n 543→\t\t\tfor wi := range work {\n 544→\t\t\t\terr := wi.level.toCheckpointBinary(wi.hostDir, from, to, m)\n 545→\t\t\t\tif err != nil {\n 546→\t\t\t\t\tif err == ErrNoNewArchiveData {\n 547→\t\t\t\t\t\tcontinue\n 548→\t\t\t\t\t}\n 549→\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> binary checkpoint error for %s: %v\", wi.hostDir, err)\n 550→\t\t\t\t\tatomic.AddInt32(&errs, 1)\n 551→\t\t\t\t} else {\n 552→\t\t\t\t\tatomic.AddInt32(&n, 1)\n 553→\t\t\t\t\tsuccessMu.Lock()\n 554→\t\t\t\t\tsuccessDirs = append(successDirs, wi.hostDir)\n 555→\t\t\t\t\tsuccessMu.Unlock()\n 556→\t\t\t\t}\n 557→\t\t\t}\n 558→\t\t}()\n 559→\t}\n 560→\n 561→\tfor i := range levels {\n 562→\t\thostDir := path.Join(dir, path.Join(selectors[i]...))\n 563→\t\twork <- workItem{\n 564→\t\t\tlevel: levels[i],\n 565→\t\t\thostDir: hostDir,\n 566→\t\t\tselector: selectors[i],\n 567→\t\t}\n 568→\t}\n 569→\tclose(work)\n 570→\twg.Wait()\n 571→\n 572→\tif errs > 0 {\n 573→\t\treturn int(n), successDirs, fmt.Errorf(\"[METRICSTORE]> %d errors during binary checkpoint (%d successes)\", errs, n)\n 574→\t}\n 575→\treturn int(n), successDirs, nil\n 576→}\n 577→\n 578→// toCheckpointBinary writes a binary snapshot file for a single host-level node.\n 579→// Uses atomic rename (write to .tmp then rename) to avoid partial reads on crash.\n 580→func (l *Level) toCheckpointBinary(dir string, from, to int64, m *MemoryStore) error {\n 581→\tcf, err := l.toCheckpointFile(from, to, m)\n 582→\tif err != nil {\n 583→\t\treturn err\n 584→\t}\n 585→\tif cf == nil {\n 586→\t\treturn ErrNoNewArchiveData\n 587→\t}\n 588→\n 589→\tif err := os.MkdirAll(dir, CheckpointDirPerms); err != nil {\n 590→\t\treturn fmt.Errorf(\"mkdir %s: %w\", dir, err)\n 591→\t}\n 592→\n 593→\t// Write to a temp file first, then rename (atomic on POSIX).\n 594→\ttmpPath := path.Join(dir, fmt.Sprintf(\"%d.bin.tmp\", from))\n 595→\tfinalPath := path.Join(dir, fmt.Sprintf(\"%d.bin\", from))\n 596→\n 597→\tf, err := os.OpenFile(tmpPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, CheckpointFilePerms)\n 598→\tif err != nil {\n 599→\t\treturn fmt.Errorf(\"open binary snapshot %s: %w\", tmpPath, err)\n 600→\t}\n 601→\n 602→\tbw := bufio.NewWriter(f)\n 603→\tif err := writeBinarySnapshotFile(bw, cf); err != nil {\n 604→\t\tf.Close()\n 605→\t\tos.Remove(tmpPath)\n 606→\t\treturn fmt.Errorf(\"write binary snapshot: %w\", err)\n 607→\t}\n 608→\tif err := bw.Flush(); err != nil {\n 609→\t\tf.Close()\n 610→\t\tos.Remove(tmpPath)\n 611→\t\treturn err\n 612→\t}\n 613→\tf.Close()\n 614→\n 615→\treturn os.Rename(tmpPath, finalPath)\n 616→}\n 617→\n 618→// writeBinarySnapshotFile writes the binary snapshot file header and level tree.\n 619→func writeBinarySnapshotFile(w io.Writer, cf *CheckpointFile) error {\n 620→\tif err := binary.Write(w, binary.LittleEndian, snapFileMagic); err != nil {\n 621→\t\treturn err\n 622→\t}\n 623→\tif err := binary.Write(w, binary.LittleEndian, cf.From); err != nil {\n 624→\t\treturn err\n 625→\t}\n 626→\tif err := binary.Write(w, binary.LittleEndian, cf.To); err != nil {\n 627→\t\treturn err\n 628→\t}\n 629→\treturn writeBinaryLevel(w, cf)\n 630→}\n 631→\n 632→// writeBinaryLevel recursively writes a CheckpointFile level in binary format.\n 633→func writeBinaryLevel(w io.Writer, cf *CheckpointFile) error {\n 634→\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Metrics))); err != nil {\n 635→\t\treturn err\n 636→\t}\n 637→\n 638→\tfor name, metric := range cf.Metrics {\n 639→\t\tif err := writeString16(w, name); err != nil {\n 640→\t\t\treturn err\n 641→\t\t}\n 642→\t\tif err := binary.Write(w, binary.LittleEndian, metric.Frequency); err != nil {\n 643→\t\t\treturn err\n 644→\t\t}\n 645→\t\tif err := binary.Write(w, binary.LittleEndian, metric.Start); err != nil {\n 646→\t\t\treturn err\n 647→\t\t}\n 648→\t\tif err := binary.Write(w, binary.LittleEndian, uint32(len(metric.Data))); err != nil {\n 649→\t\t\treturn err\n 650→\t\t}\n 651→\t\tfor _, v := range metric.Data {\n 652→\t\t\tif err := binary.Write(w, binary.LittleEndian, math.Float32bits(float32(v))); err != nil {\n 653→\t\t\t\treturn err\n 654→\t\t\t}\n 655→\t\t}\n 656→\t}\n 657→\n 658→\tif err := binary.Write(w, binary.LittleEndian, uint32(len(cf.Children))); err != nil {\n 659→\t\treturn err\n 660→\t}\n 661→\n 662→\tfor name, child := range cf.Children {\n 663→\t\tif err := writeString16(w, name); err != nil {\n 664→\t\t\treturn err\n 665→\t\t}\n 666→\t\tif err := writeBinaryLevel(w, child); err != nil {\n 667→\t\t\treturn err\n 668→\t\t}\n 669→\t}\n 670→\n 671→\treturn nil\n 672→}\n 673→\n 674→// writeString16 writes a 2-byte length-prefixed string to w.\n 675→func writeString16(w io.Writer, s string) error {\n 676→\tif err := binary.Write(w, binary.LittleEndian, uint16(len(s))); err != nil {\n 677→\t\treturn err\n 678→\t}\n 679→\t_, err := io.WriteString(w, s)\n 680→\treturn err\n 681→}\n 682→\n 683→// loadBinaryFile reads a binary snapshot file and loads data into the Level tree.\n 684→// The retention check (from) is applied to the file's 'to' timestamp.\n 685→func (l *Level) loadBinaryFile(m *MemoryStore, f *os.File, from int64) error {\n 686→\tbr := bufio.NewReader(f)\n 687→\n 688→\tvar magic uint32\n 689→\tif err := binary.Read(br, binary.LittleEndian, &magic); err != nil {\n 690→\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read magic: %w\", err)\n 691→\t}\n 692→\tif magic != snapFileMagic {\n 693→\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: invalid magic 0x%08X (expected 0x%08X)\", magic, snapFileMagic)\n 694→\t}\n 695→\n 696→\tvar fileFrom, fileTo int64\n 697→\tif err := binary.Read(br, binary.LittleEndian, &fileFrom); err != nil {\n 698→\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read from: %w\", err)\n 699→\t}\n 700→\tif err := binary.Read(br, binary.LittleEndian, &fileTo); err != nil {\n 701→\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read to: %w\", err)\n 702→\t}\n 703→\n 704→\tif fileTo != 0 && fileTo < from {\n 705→\t\treturn nil // File is older than retention window, skip it\n 706→\t}\n 707→\n 708→\tcf, err := readBinaryLevel(br)\n 709→\tif err != nil {\n 710→\t\treturn fmt.Errorf(\"[METRICSTORE]> binary snapshot: read level tree: %w\", err)\n 711→\t}\n 712→\tcf.From = fileFrom\n 713→\tcf.To = fileTo\n 714→\n 715→\treturn l.loadFile(cf, m)\n 716→}\n 717→\n 718→// readBinaryLevel recursively reads a level from the binary snapshot format.\n 719→func readBinaryLevel(r io.Reader) (*CheckpointFile, error) {\n 720→\tcf := &CheckpointFile{\n 721→\t\tMetrics: make(map[string]*CheckpointMetrics),\n 722→\t\tChildren: make(map[string]*CheckpointFile),\n 723→\t}\n 724→\n 725→\tvar numMetrics uint32\n 726→\tif err := binary.Read(r, binary.LittleEndian, &numMetrics); err != nil {\n 727→\t\treturn nil, fmt.Errorf(\"read num_metrics: %w\", err)\n 728→\t}\n 729→\n 730→\tfor range numMetrics {\n 731→\t\tname, err := readString16(r)\n 732→\t\tif err != nil {\n 733→\t\t\treturn nil, fmt.Errorf(\"read metric name: %w\", err)\n 734→\t\t}\n 735→\n 736→\t\tvar freq, start int64\n 737→\t\tif err := binary.Read(r, binary.LittleEndian, &freq); err != nil {\n 738→\t\t\treturn nil, fmt.Errorf(\"read frequency for %s: %w\", name, err)\n 739→\t\t}\n 740→\t\tif err := binary.Read(r, binary.LittleEndian, &start); err != nil {\n 741→\t\t\treturn nil, fmt.Errorf(\"read start for %s: %w\", name, err)\n 742→\t\t}\n 743→\n 744→\t\tvar numValues uint32\n 745→\t\tif err := binary.Read(r, binary.LittleEndian, &numValues); err != nil {\n 746→\t\t\treturn nil, fmt.Errorf(\"read num_values for %s: %w\", name, err)\n 747→\t\t}\n 748→\n 749→\t\tdata := make([]schema.Float, numValues)\n 750→\t\tfor i := range numValues {\n 751→\t\t\tvar bits uint32\n 752→\t\t\tif err := binary.Read(r, binary.LittleEndian, &bits); err != nil {\n 753→\t\t\t\treturn nil, fmt.Errorf(\"read value[%d] for %s: %w\", i, name, err)\n 754→\t\t\t}\n 755→\t\t\tdata[i] = schema.Float(math.Float32frombits(bits))\n 756→\t\t}\n 757→\n 758→\t\tcf.Metrics[name] = &CheckpointMetrics{\n 759→\t\t\tFrequency: freq,\n 760→\t\t\tStart: start,\n 761→\t\t\tData: data,\n 762→\t\t}\n 763→\t}\n 764→\n 765→\tvar numChildren uint32\n 766→\tif err := binary.Read(r, binary.LittleEndian, &numChildren); err != nil {\n 767→\t\treturn nil, fmt.Errorf(\"read num_children: %w\", err)\n 768→\t}\n 769→\n 770→\tfor range numChildren {\n 771→\t\tchildName, err := readString16(r)\n 772→\t\tif err != nil {\n 773→\t\t\treturn nil, fmt.Errorf(\"read child name: %w\", err)\n 774→\t\t}\n 775→\n 776→\t\tchild, err := readBinaryLevel(r)\n 777→\t\tif err != nil {\n 778→\t\t\treturn nil, fmt.Errorf(\"read child %s: %w\", childName, err)\n 779→\t\t}\n 780→\t\tcf.Children[childName] = child\n 781→\t}\n 782→\n 783→\treturn cf, nil\n 784→}\n 785→\n 786→// readString16 reads a 2-byte length-prefixed string from r.\n 787→func readString16(r io.Reader) (string, error) {\n 788→\tvar sLen uint16\n 789→\tif err := binary.Read(r, binary.LittleEndian, &sLen); err != nil {\n 790→\t\treturn \"\", err\n 791→\t}\n 792→\tbuf := make([]byte, sLen)\n 793→\tif _, err := io.ReadFull(r, buf); err != nil {\n 794→\t\treturn \"\", err\n 795→\t}\n 796→\treturn string(buf), nil\n 797→}\n 798→"}]},"uuid":"c575f94f-cc65-4ca8-8ddd-1aa26f11dfee","timestamp":"2026-03-13T08:03:16.027Z","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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 for one host directory.\ntype walFileState struct {\n\tf *os.File\n}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws.f\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\thostFiles[hostDir] = &walFileState{f: f}\n\t\t\treturn f\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tf := getOrOpenWAL(hostDir)\n\t\t\tif f == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(f, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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","numLines":798,"startLine":1,"totalLines":798}},"sourceToolAssistantUUID":"cde1dce7-08e3-41fa-a1d4-de5510c3f1dc","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"39b1f14e-19a6-42c2-8fce-2d16a2770db7","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01RjX8AuT1dcze7J7SdFvzNG","type":"tool_result","content":" 110→// Loaded from cc-backend's config.json \"metricstore\" section. Controls memory usage,\n 111→// persistence, archiving, and metric ingestion.\n 112→//\n 113→// Fields:\n 114→// - NumWorkers: Parallel workers for checkpoint/archive (0 = auto: min(NumCPU/2+1, 10))\n 115→// - RetentionInMemory: Duration string (e.g., \"48h\") for in-memory data retention\n 116→// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded\n 117→// - Checkpoints: Periodic persistence configuration\n 118→// - Debug: Development/profiling options (nil = disabled)\n 119→// - Archive: Long-term storage configuration (nil = disabled)\n 120→// - Subscriptions: NATS topics for metric ingestion (nil = polling only)\n 121→type MetricStoreConfig struct {\n 122→\t// Number of concurrent workers for checkpoint and archive operations.\n 123→\t// If not set or 0, defaults to min(runtime.NumCPU()/2+1, 10)\n 124→\tNumWorkers int `json:\"num-workers\"`"}]},"uuid":"d567ec49-a00a-4fdf-8bb0-175df2bd3d16","timestamp":"2026-03-13T08:03:16.450Z","toolUseResult":{"type":"text","file":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/config.go","content":"// Loaded from cc-backend's config.json \"metricstore\" section. Controls memory usage,\n// persistence, archiving, and metric ingestion.\n//\n// Fields:\n// - NumWorkers: Parallel workers for checkpoint/archive (0 = auto: min(NumCPU/2+1, 10))\n// - RetentionInMemory: Duration string (e.g., \"48h\") for in-memory data retention\n// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded\n// - Checkpoints: Periodic persistence configuration\n// - Debug: Development/profiling options (nil = disabled)\n// - Archive: Long-term storage configuration (nil = disabled)\n// - Subscriptions: NATS topics for metric ingestion (nil = polling only)\ntype MetricStoreConfig struct {\n\t// Number of concurrent workers for checkpoint and archive operations.\n\t// If not set or 0, defaults to min(runtime.NumCPU()/2+1, 10)\n\tNumWorkers int `json:\"num-workers\"`","numLines":15,"startLine":110,"totalLines":255}},"sourceToolAssistantUUID":"39b1f14e-19a6-42c2-8fce-2d16a2770db7","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"d567ec49-a00a-4fdf-8bb0-175df2bd3d16","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01EayjnHu9NvPPTPJNrwWv1t","type":"message","role":"assistant","content":[{"type":"thinking","thinking":"","signature":"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"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":11655,"cache_read_input_tokens":18710,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":11655},"output_tokens":8,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CYzjLcpzdYcxEJpKjT6yg","type":"assistant","uuid":"7fad88e5-284a-49a1-832b-835fb08be146","timestamp":"2026-03-13T08:03:25.258Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"7fad88e5-284a-49a1-832b-835fb08be146","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01EayjnHu9NvPPTPJNrwWv1t","type":"message","role":"assistant","content":[{"type":"text","text":"Now I'll implement both improvements. Let me start with all the edits.\n\n**Improvement 1: WAL buffering** — Add `bufio.Writer` to `walFileState` and use it throughout.\n\n**Improvement 3: Fix MemoryCap comment.**"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":11655,"cache_read_input_tokens":18710,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":11655},"output_tokens":8,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CYzjLcpzdYcxEJpKjT6yg","type":"assistant","uuid":"5c0abb68-5b89-43db-96a6-93262bdc086a","timestamp":"2026-03-13T08:03:26.242Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"15af7cb6-9db4-4588-8030-8d8d99881158","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01WuetEHX1drYV4PwcCrgL4z","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"b64f5cc6-b943-4c71-b89c-58221cc38338","timestamp":"2026-03-13T08:03:28.371Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"// walFileState holds an open WAL file handle for one host directory.\ntype walFileState struct {\n\tf *os.File\n}","newString":"// 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}","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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 for one host directory.\ntype walFileState struct {\n\tf *os.File\n}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws.f\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\thostFiles[hostDir] = &walFileState{f: f}\n\t\t\treturn f\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tf := getOrOpenWAL(hostDir)\n\t\t\tif f == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(f, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":106,"oldLines":9,"newStart":106,"newLines":10,"lines":[" done chan struct{}"," }"," ","-// walFileState holds an open WAL file handle for one host directory.","+// walFileState holds an open WAL file handle and buffered writer for one host directory."," type walFileState struct {"," f *os.File","+ w *bufio.Writer"," }"," "," // WALStaging starts a background goroutine that receives WALMessage items"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"15af7cb6-9db4-4588-8030-8d8d99881158","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"f9d526f1-9b8e-440a-83d2-09111b6770c5","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01FrMEm92D8UcFGUcAMpBHWZ","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"d20cf8a4-64ed-4101-87d6-d726bca2e2cc","timestamp":"2026-03-13T08:03:32.041Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()","newString":"\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws.f\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\thostFiles[hostDir] = &walFileState{f: f}\n\t\t\treturn f\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tf := getOrOpenWAL(hostDir)\n\t\t\tif f == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(f, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":126,"oldLines":6,"newStart":126,"newLines":7,"lines":[" defer func() {"," for _, ws := range hostFiles {"," if ws.f != nil {","+ ws.w.Flush()"," ws.f.Close()"," }"," }"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"f9d526f1-9b8e-440a-83d2-09111b6770c5","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"d20cf8a4-64ed-4101-87d6-d726bca2e2cc","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CPiFo3gZo2o2Mykt9n43sv","type":"message","role":"assistant","content":[{"type":"text","text":"Now change `getOrOpenWAL` to return `*walFileState` and wrap the file with a `bufio.Writer`:"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":276,"cache_read_input_tokens":31000,"cache_creation":{"ephemeral_5m_input_tokens":276,"ephemeral_1h_input_tokens":0},"output_tokens":1,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CYzjMmWR7JeF3WVtGCo51","type":"assistant","uuid":"f481149d-6d8e-49a1-acb2-c9b31ef6c65c","timestamp":"2026-03-13T08:03:37.749Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"f481149d-6d8e-49a1-acb2-c9b31ef6c65c","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01CPiFo3gZo2o2Mykt9n43sv","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01APuPomfy3Cy5ES5VMwug2C","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","old_string":"\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws.f\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\thostFiles[hostDir] = &walFileState{f: f}\n\t\t\treturn f\n\t\t}","new_string":"\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tws = &walFileState{f: f, w: w}\n\t\t\thostFiles[hostDir] = ws\n\t\t\treturn ws\n\t\t}"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":276,"cache_read_input_tokens":31000,"output_tokens":946,"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":276},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjMmWR7JeF3WVtGCo51","type":"assistant","uuid":"57d6b745-fd0f-4071-883a-2711e6b40917","timestamp":"2026-03-13T08:03:45.553Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"57d6b745-fd0f-4071-883a-2711e6b40917","isSidechain":false,"type":"progress","data":{"type":"hook_progress","hookEvent":"PostToolUse","hookName":"PostToolUse:Edit","command":"callback"},"parentToolUseID":"toolu_01APuPomfy3Cy5ES5VMwug2C","toolUseID":"toolu_01APuPomfy3Cy5ES5VMwug2C","timestamp":"2026-03-13T08:03:45.565Z","uuid":"6ea0e261-2eeb-4c3c-a919-29189061e4d7","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"57d6b745-fd0f-4071-883a-2711e6b40917","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01APuPomfy3Cy5ES5VMwug2C","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"4f92ab32-0d09-4b9c-947d-eae5823aca89","timestamp":"2026-03-13T08:03:45.564Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws.f\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\thostFiles[hostDir] = &walFileState{f: f}\n\t\t\treturn f\n\t\t}","newString":"\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tws = &walFileState{f: f, w: w}\n\t\t\thostFiles[hostDir] = ws\n\t\t\treturn ws\n\t\t}","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws.f\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\thostFiles[hostDir] = &walFileState{f: f}\n\t\t\treturn f\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tf := getOrOpenWAL(hostDir)\n\t\t\tif f == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(f, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":132,"oldLines":10,"newStart":132,"newLines":10,"lines":[" }"," }()"," ","- getOrOpenWAL := func(hostDir string) *os.File {","+ getOrOpenWAL := func(hostDir string) *walFileState {"," ws, ok := hostFiles[hostDir]"," if ok {","- return ws.f","+ return ws"," }"," "," if err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {"]},{"oldStart":150,"oldLines":20,"newStart":150,"newLines":23,"lines":[" return nil"," }"," ","+ w := bufio.NewWriter(f)","+"," // Write file header magic if file is new (empty)."," info, err := f.Stat()"," if err == nil && info.Size() == 0 {"," var hdr [4]byte"," binary.LittleEndian.PutUint32(hdr[:], walFileMagic)","- if _, err := f.Write(hdr[:]); err != nil {","+ if _, err := w.Write(hdr[:]); err != nil {"," cclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)"," f.Close()"," return nil"," }"," }"," ","- hostFiles[hostDir] = &walFileState{f: f}","- return f","+ ws = &walFileState{f: f, w: w}","+ hostFiles[hostDir] = ws","+ return ws"," }"," "," processMsg := func(msg *WALMessage) {"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"57d6b745-fd0f-4071-883a-2711e6b40917","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"a8b0c9d2-0abc-4e37-b494-fec2e1a1be10","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_018f7qvUxGMvbQ5wndcRdiQ6","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"c4611ab5-54d1-4825-8ea7-6cb920cc6418","timestamp":"2026-03-13T08:03:51.186Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tf := getOrOpenWAL(hostDir)\n\t\t\tif f == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(f, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}","newString":"\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\tif ws == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(ws.w, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tws = &walFileState{f: f, w: w}\n\t\t\thostFiles[hostDir] = ws\n\t\t\treturn ws\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tf := getOrOpenWAL(hostDir)\n\t\t\tif f == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(f, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":171,"oldLines":11,"newStart":171,"newLines":11,"lines":[" "," processMsg := func(msg *WALMessage) {"," hostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)","- f := getOrOpenWAL(hostDir)","- if f == nil {","+ ws := getOrOpenWAL(hostDir)","+ if ws == nil {"," return"," }","- if err := writeWALRecord(f, msg); err != nil {","+ if err := writeWALRecord(ws.w, msg); err != nil {"," cclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)"," }"," }"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"a8b0c9d2-0abc-4e37-b494-fec2e1a1be10","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"37b40d4d-ffe8-4946-9adb-33f02075b3a8","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01UNERQNa4FzWNHUaBKkWKzh","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_019xVBEqjuoJKKDUnm78yevb","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","old_string":"\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}","new_string":"\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.w.Flush()\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":635,"cache_read_input_tokens":32269,"output_tokens":464,"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":635},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjPBRNAA59qKULDdCdH","type":"assistant","uuid":"629b1723-446b-4330-a0a9-65b3a048714c","timestamp":"2026-03-13T08:03:57.108Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"629b1723-446b-4330-a0a9-65b3a048714c","isSidechain":false,"type":"progress","data":{"type":"hook_progress","hookEvent":"PostToolUse","hookName":"PostToolUse:Edit","command":"callback"},"parentToolUseID":"toolu_019xVBEqjuoJKKDUnm78yevb","toolUseID":"toolu_019xVBEqjuoJKKDUnm78yevb","timestamp":"2026-03-13T08:03:57.125Z","uuid":"d031e94d-e541-4547-9db9-3faf4fcbb06a","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"629b1723-446b-4330-a0a9-65b3a048714c","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_019xVBEqjuoJKKDUnm78yevb","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"3087c8a5-8d29-4494-89d0-0c8d2a554ba8","timestamp":"2026-03-13T08:03:57.124Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}","newString":"\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.w.Flush()\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tws = &walFileState{f: f, w: w}\n\t\t\thostFiles[hostDir] = ws\n\t\t\treturn ws\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\tif ws == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(ws.w, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":183,"oldLines":6,"newStart":183,"newLines":7,"lines":[" processRotate := func(req walRotateReq) {"," ws, ok := hostFiles[req.hostDir]"," if ok && ws.f != nil {","+ ws.w.Flush()"," ws.f.Close()"," walPath := path.Join(req.hostDir, \"current.wal\")"," if err := os.Remove(walPath); 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{"parentUuid":"b07542a8-efab-4943-824d-cad4543386b0","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01JGm4GscAK5K5XgbZBx4duj","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"a8cf2d2a-3f23-4048-852e-c8a34b4fa53c","timestamp":"2026-03-13T08:04:02.329Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}","newString":"\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\t// Flush all buffered writers after draining remaining messages.\n\t\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\t\tif ws.f != nil {\n\t\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\t}\n\t\t\t\t\t}\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}","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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tws = &walFileState{f: f, w: w}\n\t\t\thostFiles[hostDir] = ws\n\t\t\treturn ws\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\tif ws == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(ws.w, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.w.Flush()\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":205,"oldLines":6,"newStart":205,"newLines":12,"lines":[" case req := <-walRotateCh:"," processRotate(req)"," default:","+ // Flush all buffered writers after draining remaining messages.","+ for _, ws := range hostFiles {","+ if ws.f != nil {","+ ws.w.Flush()","+ }","+ }"," return"," }"," }"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"b07542a8-efab-4943-824d-cad4543386b0","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"10c682ac-9e6a-4aaa-99a8-21ff4b146ace","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_018u3kj274fyS3WeADdHT71r","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_016trXqxsLdczWU3A7PhFn7T","name":"Edit","input":{"replace_all":false,"file_path":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","old_string":"// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn err\n}","new_string":"// writeWALRecord appends a binary WAL record to the writer.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(w io.Writer, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := w.Write(record)\n\treturn err\n}"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":410,"cache_read_input_tokens":33507,"output_tokens":732,"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":410},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjPzy6Yfaa6SCd9fvBg","type":"assistant","uuid":"25c25101-25bd-4083-b7e7-9a1b6c9cba4a","timestamp":"2026-03-13T08:04:10.541Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"25c25101-25bd-4083-b7e7-9a1b6c9cba4a","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_016trXqxsLdczWU3A7PhFn7T","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go has been updated successfully."}]},"uuid":"9e503058-33ef-445b-93f3-5644e860a74f","timestamp":"2026-03-13T08:04:10.573Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/walCheckpoint.go","oldString":"// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn err\n}","newString":"// writeWALRecord appends a binary WAL record to the writer.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(w io.Writer, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := w.Write(record)\n\treturn err\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 <timestamp>.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 <timestamp>.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\"io\"\n\t\"math\"\n\t\"os\"\n\t\"path\"\n\t\"strings\"\n\t\"sync\"\n\t\"sync/atomic\"\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// WALMessages is the channel for sending metric writes to the WAL staging goroutine.\n// Buffered to allow burst writes without blocking the metric ingestion path.\nvar WALMessages = make(chan *WALMessage, 4096)\n\n// walRotateCh is used by the checkpoint goroutine to request WAL file rotation\n// (close, delete, reopen) after a binary snapshot has been written.\nvar walRotateCh = make(chan walRotateReq, 256)\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}\n\n// WALStaging starts a background goroutine that receives WALMessage items\n// and appends binary WAL records to per-host current.wal files.\n// Also handles WAL rotation requests from the checkpoint goroutine.\nfunc WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n\twg.Go(func() {\n\t\tif Keys.Checkpoints.FileFormat == \"json\" {\n\t\t\treturn\n\t\t}\n\n\t\thostFiles := make(map[string]*walFileState)\n\n\t\tdefer func() {\n\t\t\tfor _, ws := range hostFiles {\n\t\t\t\tif ws.f != nil {\n\t\t\t\t\tws.w.Flush()\n\t\t\t\t\tws.f.Close()\n\t\t\t\t}\n\t\t\t}\n\t\t}()\n\n\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n\t\t\tws, ok := hostFiles[hostDir]\n\t\t\tif ok {\n\t\t\t\treturn ws\n\t\t\t}\n\n\t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: mkdir %s: %v\", hostDir, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\twalPath := path.Join(hostDir, \"current.wal\")\n\t\t\tf, err := os.OpenFile(walPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, CheckpointFilePerms)\n\t\t\tif err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: open %s: %v\", walPath, err)\n\t\t\t\treturn nil\n\t\t\t}\n\n\t\t\tw := bufio.NewWriter(f)\n\n\t\t\t// Write file header magic if file is new (empty).\n\t\t\tinfo, err := f.Stat()\n\t\t\tif err == nil && info.Size() == 0 {\n\t\t\t\tvar hdr [4]byte\n\t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n\t\t\t\t\tf.Close()\n\t\t\t\t\treturn nil\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tws = &walFileState{f: f, w: w}\n\t\t\thostFiles[hostDir] = ws\n\t\t\treturn ws\n\t\t}\n\n\t\tprocessMsg := func(msg *WALMessage) {\n\t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n\t\t\tws := getOrOpenWAL(hostDir)\n\t\t\tif ws == nil {\n\t\t\t\treturn\n\t\t\t}\n\t\t\tif err := writeWALRecord(ws.w, msg); err != nil {\n\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n\t\t\t}\n\t\t}\n\n\t\tprocessRotate := func(req walRotateReq) {\n\t\t\tws, ok := hostFiles[req.hostDir]\n\t\t\tif ok && ws.f != nil {\n\t\t\t\tws.w.Flush()\n\t\t\t\tws.f.Close()\n\t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n\t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n\t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: remove %s: %v\", walPath, err)\n\t\t\t\t}\n\t\t\t\tdelete(hostFiles, req.hostDir)\n\t\t\t}\n\t\t\tclose(req.done)\n\t\t}\n\n\t\tdrain := func() {\n\t\t\tfor {\n\t\t\t\tselect {\n\t\t\t\tcase msg, ok := <-WALMessages:\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\tcase req := <-walRotateCh:\n\t\t\t\t\tprocessRotate(req)\n\t\t\t\tdefault:\n\t\t\t\t\t// Flush all buffered writers after draining remaining messages.\n\t\t\t\t\tfor _, ws := range hostFiles {\n\t\t\t\t\t\tif ws.f != nil {\n\t\t\t\t\t\t\tws.w.Flush()\n\t\t\t\t\t\t}\n\t\t\t\t\t}\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t}\n\t\t}\n\n\t\tfor {\n\t\t\tselect {\n\t\t\tcase <-ctx.Done():\n\t\t\t\tdrain()\n\t\t\t\treturn\n\t\t\tcase msg, ok := <-WALMessages:\n\t\t\t\tif !ok {\n\t\t\t\t\treturn\n\t\t\t\t}\n\t\t\t\tprocessMsg(msg)\n\t\t\tcase req := <-walRotateCh:\n\t\t\t\tprocessRotate(req)\n\t\t\t}\n\t\t}\n\t})\n}\n\n// RotateWALFiles sends rotation requests for the given host directories\n// and blocks until all rotations complete.\nfunc RotateWALFiles(hostDirs []string) {\n\tdones := make([]chan struct{}, len(hostDirs))\n\tfor i, dir := range hostDirs {\n\t\tdones[i] = make(chan struct{})\n\t\twalRotateCh <- walRotateReq{hostDir: dir, done: dones[i]}\n\t}\n\tfor _, done := range dones {\n\t\t<-done\n\t}\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// buildWALPayload encodes a WALMessage into a binary payload (without magic/length/CRC).\nfunc buildWALPayload(msg *WALMessage) []byte {\n\tsize := 8 + 2 + len(msg.MetricName) + 1 + 4\n\tfor _, s := range msg.Selector {\n\t\tsize += 1 + len(s)\n\t}\n\n\tbuf := make([]byte, 0, size)\n\n\t// Timestamp (8 bytes, little-endian int64)\n\tvar ts [8]byte\n\tbinary.LittleEndian.PutUint64(ts[:], uint64(msg.Timestamp))\n\tbuf = append(buf, ts[:]...)\n\n\t// Metric name (2-byte length prefix + bytes)\n\tvar mLen [2]byte\n\tbinary.LittleEndian.PutUint16(mLen[:], uint16(len(msg.MetricName)))\n\tbuf = append(buf, mLen[:]...)\n\tbuf = append(buf, msg.MetricName...)\n\n\t// Selector count (1 byte)\n\tbuf = append(buf, byte(len(msg.Selector)))\n\n\t// Selectors (1-byte length prefix + bytes each)\n\tfor _, sel := range msg.Selector {\n\t\tbuf = append(buf, byte(len(sel)))\n\t\tbuf = append(buf, sel...)\n\t}\n\n\t// Value (4 bytes, float32 bit representation)\n\tvar val [4]byte\n\tbinary.LittleEndian.PutUint32(val[:], math.Float32bits(float32(msg.Value)))\n\tbuf = append(buf, val[:]...)\n\n\treturn buf\n}\n\n// writeWALRecord appends a binary WAL record to the file.\n// Format: [4B magic][4B payload_len][payload][4B CRC32]\nfunc writeWALRecord(f *os.File, msg *WALMessage) error {\n\tpayload := buildWALPayload(msg)\n\tcrc := crc32.ChecksumIEEE(payload)\n\n\trecord := make([]byte, 0, 4+4+len(payload)+4)\n\n\tvar magic [4]byte\n\tbinary.LittleEndian.PutUint32(magic[:], walRecordMagic)\n\trecord = append(record, magic[:]...)\n\n\tvar pLen [4]byte\n\tbinary.LittleEndian.PutUint32(pLen[:], uint32(len(payload)))\n\trecord = append(record, pLen[:]...)\n\n\trecord = append(record, payload...)\n\n\tvar crcBytes [4]byte\n\tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n\trecord = append(record, crcBytes[:]...)\n\n\t_, err := f.Write(record)\n\treturn 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\tn, errs := 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\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\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\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}\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\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":294,"oldLines":9,"newStart":294,"newLines":9,"lines":[" return buf"," }"," ","-// writeWALRecord appends a binary WAL record to the file.","+// writeWALRecord appends a binary WAL record to the writer."," // Format: [4B magic][4B payload_len][payload][4B CRC32]","-func writeWALRecord(f *os.File, msg *WALMessage) error {","+func writeWALRecord(w io.Writer, msg *WALMessage) error {"," payload := buildWALPayload(msg)"," crc := crc32.ChecksumIEEE(payload)"," "]},{"oldStart":316,"oldLines":7,"newStart":316,"newLines":7,"lines":[" binary.LittleEndian.PutUint32(crcBytes[:], crc)"," record = append(record, crcBytes[:]...)"," ","- _, err := f.Write(record)","+ _, err := w.Write(record)"," return err"," }"," "]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"25c25101-25bd-4083-b7e7-9a1b6c9cba4a","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"e401adc7-671e-4d70-9660-4d150340b4b9","isSidechain":false,"promptId":"5f4feea4-c535-43c4-b8a0-870df0f56606","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01Ekn23gFpytCB6D9VwfAGsj","type":"tool_result","content":"The file /Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/config.go has been updated successfully."}]},"uuid":"0f8dde12-4563-4704-af93-abdc791562dd","timestamp":"2026-03-13T08:04:17.405Z","toolUseResult":{"filePath":"/Users/jan/prg/ClusterCockpit/cc-backend/pkg/metricstore/config.go","oldString":"// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded","newString":"// - MemoryCap: Max memory in GB for buffer data (0 = unlimited); triggers forceFree when exceeded","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 config.go: Configuration structures and metric management.\n//\n// # Configuration Hierarchy\n//\n// The metricstore package uses nested configuration structures:\n//\n//\tMetricStoreConfig (Keys)\n//\t├─ NumWorkers: Parallel checkpoint/archive workers\n//\t├─ RetentionInMemory: How long to keep data in RAM (also used as cleanup interval)\n//\t├─ MemoryCap: Memory limit in bytes (triggers forceFree)\n//\t├─ Checkpoints: Persistence configuration\n//\t│ ├─ FileFormat: \"json\" or \"wal\" (default: \"wal\")\n//\t│ └─ RootDir: Checkpoint storage path\n//\t├─ Cleanup: Long-term storage configuration (interval = RetentionInMemory)\n//\t│ ├─ RootDir: Archive storage path (archive mode only)\n//\t│ └─ Mode: \"delete\" or \"archive\"\n//\t├─ Debug: Development/debugging options\n//\t└─ Subscriptions: NATS topic subscriptions for metric ingestion\n//\n// # Metric Configuration\n//\n// Each metric (e.g., \"cpu_load\", \"mem_used\") has a MetricConfig entry in the global\n// Metrics map, defining:\n//\n// - Frequency: Measurement interval in seconds\n// - Aggregation: How to combine values (sum/avg/none) when transforming scopes\n// - offset: Internal index into Level.metrics slice (assigned during Init)\n//\n// # AggregationStrategy\n//\n// Determines how to combine metric values when aggregating from finer to coarser scopes:\n//\n// - NoAggregation: Do not combine (incompatible scopes)\n// - SumAggregation: Add values (e.g., power consumption: core→socket)\n// - AvgAggregation: Average values (e.g., temperature: core→socket)\npackage metricstore\n\nimport (\n\t\"fmt\"\n\t\"time\"\n\n\t\"github.com/ClusterCockpit/cc-backend/pkg/archive\"\n\tcclog \"github.com/ClusterCockpit/cc-lib/v2/ccLogger\"\n\t\"github.com/ClusterCockpit/cc-lib/v2/schema\"\n)\n\nconst (\n\tDefaultMaxWorkers = 10\n\tDefaultBufferCapacity = 512\n\tDefaultGCTriggerInterval = 100\n\tDefaultMemoryUsageTrackerInterval = 5 * time.Minute\n)\n\n// Checkpoints configures periodic persistence of in-memory metric data.\n//\n// Fields:\n// - FileFormat: \"json\" (human-readable, periodic) or \"wal\" (binary snapshot + WAL, crash-safe); default is \"wal\"\n// - RootDir: Filesystem path for checkpoint files (created if missing)\ntype Checkpoints struct {\n\tFileFormat string `json:\"file-format\"`\n\tRootDir string `json:\"directory\"`\n}\n\n// Debug provides development and profiling options.\n//\n// Fields:\n// - DumpToFile: Path to dump checkpoint data for inspection (empty = disabled)\n// - EnableGops: Enable gops agent for live runtime debugging (https://github.com/google/gops)\ntype Debug struct {\n\tDumpToFile string `json:\"dump-to-file\"`\n\tEnableGops bool `json:\"gops\"`\n}\n\n// Cleanup configures long-term storage of old metric data.\n//\n// Data older than RetentionInMemory is archived to disk or deleted.\n// The cleanup interval is always RetentionInMemory.\n//\n// Fields:\n// - RootDir: Filesystem path for archived data (used in \"archive\" mode)\n// - Mode: \"delete\" (discard old data) or \"archive\" (write to RootDir)\ntype Cleanup struct {\n\tRootDir string `json:\"directory\"`\n\tMode string `json:\"mode\"`\n}\n\n// Subscriptions defines NATS topics to subscribe to for metric ingestion.\n//\n// Each subscription receives metrics via NATS messaging, enabling real-time\n// data collection from compute nodes.\n//\n// Fields:\n// - SubscribeTo: NATS subject/channel name (e.g., \"metrics.compute.*\")\n// - ClusterTag: Default cluster name for metrics without cluster tag (optional)\ntype Subscriptions []struct {\n\t// Channel name\n\tSubscribeTo string `json:\"subscribe-to\"`\n\n\t// Allow lines without a cluster tag, use this as default, optional\n\tClusterTag string `json:\"cluster-tag\"`\n}\n\n// MetricStoreConfig defines the main configuration for the metricstore.\n//\n// Loaded from cc-backend's config.json \"metricstore\" section. Controls memory usage,\n// persistence, archiving, and metric ingestion.\n//\n// Fields:\n// - NumWorkers: Parallel workers for checkpoint/archive (0 = auto: min(NumCPU/2+1, 10))\n// - RetentionInMemory: Duration string (e.g., \"48h\") for in-memory data retention\n// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded\n// - Checkpoints: Periodic persistence configuration\n// - Debug: Development/profiling options (nil = disabled)\n// - Archive: Long-term storage configuration (nil = disabled)\n// - Subscriptions: NATS topics for metric ingestion (nil = polling only)\ntype MetricStoreConfig struct {\n\t// Number of concurrent workers for checkpoint and archive operations.\n\t// If not set or 0, defaults to min(runtime.NumCPU()/2+1, 10)\n\tNumWorkers int `json:\"num-workers\"`\n\tRetentionInMemory string `json:\"retention-in-memory\"`\n\tCheckpointInterval string `json:\"checkpoint-interval,omitempty\"`\n\tMemoryCap int `json:\"memory-cap\"`\n\tCheckpoints Checkpoints `json:\"checkpoints\"`\n\tDebug *Debug `json:\"debug\"`\n\tCleanup *Cleanup `json:\"cleanup\"`\n\tSubscriptions *Subscriptions `json:\"nats-subscriptions\"`\n}\n\n// Keys is the global metricstore configuration instance.\n//\n// Initialized with defaults, then overwritten by cc-backend's config.json.\n// Accessed by Init(), Checkpointing(), and other lifecycle functions.\nvar Keys MetricStoreConfig = MetricStoreConfig{\n\tCheckpoints: Checkpoints{\n\t\tFileFormat: \"wal\",\n\t\tRootDir: \"./var/checkpoints\",\n\t},\n\tCleanup: &Cleanup{\n\t\tMode: \"delete\",\n\t},\n}\n\n// AggregationStrategy defines how to combine metric values across hierarchy levels.\n//\n// Used when transforming data from finer-grained scopes (e.g., core) to coarser scopes\n// (e.g., socket). This is SPATIAL aggregation, not TEMPORAL (time-based) aggregation.\n//\n// Values:\n// - NoAggregation: Do not aggregate (incompatible scopes or non-aggregatable metrics)\n// - SumAggregation: Add values (e.g., power: sum core power → socket power)\n// - AvgAggregation: Average values (e.g., temperature: average core temps → socket temp)\ntype AggregationStrategy int\n\nconst (\n\tNoAggregation AggregationStrategy = iota // Do not aggregate\n\tSumAggregation // Sum values (e.g., power, energy)\n\tAvgAggregation // Average values (e.g., temperature, utilization)\n)\n\n// AssignAggregationStrategy parses a string into an AggregationStrategy value.\n//\n// Used when loading metric configurations from JSON/YAML files.\n//\n// Parameters:\n// - str: \"sum\", \"avg\", or \"\" (empty string for NoAggregation)\n//\n// Returns:\n// - AggregationStrategy: Parsed value\n// - error: Non-nil if str is unrecognized\nfunc AssignAggregationStrategy(str string) (AggregationStrategy, error) {\n\tswitch str {\n\tcase \"\":\n\t\treturn NoAggregation, nil\n\tcase \"sum\":\n\t\treturn SumAggregation, nil\n\tcase \"avg\":\n\t\treturn AvgAggregation, nil\n\tdefault:\n\t\treturn NoAggregation, fmt.Errorf(\"[METRICSTORE]> unknown aggregation strategy: %s\", str)\n\t}\n}\n\n// MetricConfig defines configuration for a single metric type.\n//\n// Stored in the global Metrics map, keyed by metric name (e.g., \"cpu_load\").\n//\n// Fields:\n// - Frequency: Measurement interval in seconds (e.g., 60 for 1-minute granularity)\n// - Aggregation: How to combine values across hierarchy levels (sum/avg/none)\n// - offset: Internal index into Level.metrics slice (assigned during Init)\ntype MetricConfig struct {\n\t// Interval in seconds at which measurements are stored\n\tFrequency int64\n\n\t// Can be 'sum', 'avg' or null. Describes how to aggregate metrics from the same timestep over the hierarchy.\n\tAggregation AggregationStrategy\n\n\t// Private, used internally...\n\toffset int\n}\n\nfunc BuildMetricList() map[string]MetricConfig {\n\tvar metrics map[string]MetricConfig = make(map[string]MetricConfig)\n\n\taddMetric := func(name string, metric MetricConfig) error {\n\t\tif metrics == nil {\n\t\t\tmetrics = make(map[string]MetricConfig, 0)\n\t\t}\n\n\t\tif existingMetric, ok := metrics[name]; ok {\n\t\t\tif existingMetric.Frequency != metric.Frequency {\n\t\t\t\tif existingMetric.Frequency < metric.Frequency {\n\t\t\t\t\texistingMetric.Frequency = metric.Frequency\n\t\t\t\t\tmetrics[name] = existingMetric\n\t\t\t\t}\n\t\t\t}\n\t\t} else {\n\t\t\tmetrics[name] = metric\n\t\t}\n\n\t\treturn nil\n\t}\n\n\t// Helper function to add metric configuration\n\taddMetricConfig := func(mc *schema.MetricConfig) {\n\t\tagg, err := AssignAggregationStrategy(mc.Aggregation)\n\t\tif err != nil {\n\t\t\tcclog.Warnf(\"Could not find aggregation strategy for metric config '%s': %s\", mc.Name, err.Error())\n\t\t}\n\n\t\taddMetric(mc.Name, MetricConfig{\n\t\t\tFrequency: int64(mc.Timestep),\n\t\t\tAggregation: agg,\n\t\t})\n\t}\n\tfor _, c := range archive.Clusters {\n\t\tfor _, mc := range c.MetricConfig {\n\t\t\taddMetricConfig(mc)\n\t\t}\n\n\t\tfor _, sc := range c.SubClusters {\n\t\t\tfor _, mc := range sc.MetricConfig {\n\t\t\t\taddMetricConfig(mc)\n\t\t\t}\n\t\t}\n\t}\n\n\treturn metrics\n}\n","structuredPatch":[{"oldStart":113,"oldLines":7,"newStart":113,"newLines":7,"lines":[" // Fields:"," // - NumWorkers: Parallel workers for checkpoint/archive (0 = auto: min(NumCPU/2+1, 10))"," // - RetentionInMemory: Duration string (e.g., \"48h\") for in-memory data retention","-// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded","+// - MemoryCap: Max memory in GB for buffer data (0 = unlimited); triggers forceFree when exceeded"," // - Checkpoints: Periodic persistence configuration"," // - Debug: Development/profiling options (nil = disabled)"," // - Archive: Long-term storage configuration (nil = disabled)"]}],"userModified":false,"replaceAll":false},"sourceToolAssistantUUID":"e401adc7-671e-4d70-9660-4d150340b4b9","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"ca5804c4-30bb-4b7d-be72-19bb19ceae5f","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01DNC3isiUHWCucUGo3ewcGc","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_018VbXsY5xrivPWUPm4qfbhq","name":"Bash","input":{"command":"go test ./pkg/metricstore/... 2>&1","description":"Run metricstore tests","timeout":120000},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":223,"cache_read_input_tokens":34947,"output_tokens":123,"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":223},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjRReSEk9Cp9CiDDyhe","type":"assistant","uuid":"8cf1b358-6382-4a92-b194-bc547201967d","timestamp":"2026-03-13T08:04:25.100Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"df60a753-d392-42b2-bb18-135506822581","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_012aTUrNvJGiNoG5gTpStpn2","type":"message","role":"assistant","content":[{"type":"text","text":"Build and tests pass. Here's a summary of the changes:\n\n**Improvement 1 — WAL buffering** (`pkg/metricstore/walCheckpoint.go`):\n- Added `w *bufio.Writer` to `walFileState` struct\n- `getOrOpenWAL` now wraps the file with `bufio.NewWriter` and returns `*walFileState`\n- `writeWALRecord` signature changed from `*os.File` to `io.Writer` — writes go through the buffer\n- Header magic write also goes through `bufio.Writer`\n- Flush calls added in three places: `processRotate` (before close), `defer` cleanup (before close), and `drain` (after processing remaining messages)\n\n**Improvement 3 — Comment fix** (`pkg/metricstore/config.go:116`):\n- Fixed misleading comment: \"Max bytes\" → \"Max memory in GB\""}],"stop_reason":"end_turn","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":143,"cache_read_input_tokens":35170,"output_tokens":216,"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":143},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjRoAVLCY5CgdqBPwvA","type":"assistant","uuid":"9d4955d0-1727-4194-b813-5bb01ac487fa","timestamp":"2026-03-13T08:04:33.473Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"type":"file-history-snapshot","messageId":"6d302268-b4fa-46d5-8ec1-c27a9fa4a076","snapshot":{"messageId":"6d302268-b4fa-46d5-8ec1-c27a9fa4a076","trackedFileBackups":{"pkg/metricstore/walCheckpoint.go":{"backupFileName":"f5b5b4bac0274f50@v2","version":2,"backupTime":"2026-03-13T08:05:11.851Z"},"pkg/metricstore/config.go":{"backupFileName":"614b3f053f832cad@v2","version":2,"backupTime":"2026-03-13T08:05:11.852Z"}},"timestamp":"2026-03-13T08:05:11.851Z"},"isSnapshotUpdate":false}
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{"parentUuid":"5375feba-7d94-4710-bdb0-b10436c0c8ef","isSidechain":false,"promptId":"99e4087b-ecde-4d72-a0fa-e2b512929d27","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01PCraPYN4gFw8KcvWjUuMLs","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 <file>...\" to update what will be committed)\n (use \"git restore <file>...\" to discard changes in working directory)\n\tmodified: pkg/metricstore/api.go\n\tmodified: pkg/metricstore/checkpoint.go\n\tmodified: pkg/metricstore/config.go\n\tmodified: pkg/metricstore/configSchema.go\n\tmodified: pkg/metricstore/healthcheck.go\n\tmodified: pkg/metricstore/level.go\n\tmodified: pkg/metricstore/metricstore.go\n\tmodified: pkg/metricstore/stats.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":"4422bd77-060e-42c6-8afe-755a17f52196","timestamp":"2026-03-13T08:05:15.667Z","toolUseResult":{"stdout":"On branch hotfix\nYour branch is up to date with 'origin/hotfix'.\n\nChanges not staged for commit:\n (use \"git add <file>...\" to update what will be committed)\n (use \"git restore <file>...\" to discard changes in working directory)\n\tmodified: pkg/metricstore/api.go\n\tmodified: pkg/metricstore/checkpoint.go\n\tmodified: pkg/metricstore/config.go\n\tmodified: pkg/metricstore/configSchema.go\n\tmodified: pkg/metricstore/healthcheck.go\n\tmodified: pkg/metricstore/level.go\n\tmodified: pkg/metricstore/metricstore.go\n\tmodified: pkg/metricstore/stats.go\n\tmodified: pkg/metricstore/walCheckpoint.go\n\nno changes added to commit (use \"git add\" and/or \"git commit -a\")","stderr":"","interrupted":false,"isImage":false,"noOutputExpected":false},"sourceToolAssistantUUID":"5375feba-7d94-4710-bdb0-b10436c0c8ef","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"4422bd77-060e-42c6-8afe-755a17f52196","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01GQSPVvhoNG1oXVBgRrM6cR","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01BFQr6RY6hfQuL64B73u5YZ","name":"Bash","input":{"command":"git diff pkg/metricstore/walCheckpoint.go pkg/metricstore/config.go","description":"Show staged and unstaged changes"},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":282,"cache_read_input_tokens":35313,"cache_creation":{"ephemeral_5m_input_tokens":282,"ephemeral_1h_input_tokens":0},"output_tokens":26,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CYzjV8DJdwUbYZP6SrEMH","type":"assistant","uuid":"5bde0806-d34f-4d73-9a99-22bec022bd26","timestamp":"2026-03-13T08:05:16.489Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"5bde0806-d34f-4d73-9a99-22bec022bd26","isSidechain":false,"promptId":"99e4087b-ecde-4d72-a0fa-e2b512929d27","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01BFQr6RY6hfQuL64B73u5YZ","type":"tool_result","content":"diff --git a/pkg/metricstore/config.go b/pkg/metricstore/config.go\nindex 44743dbe..f6c56672 100644\n--- a/pkg/metricstore/config.go\n+++ b/pkg/metricstore/config.go\n@@ -113,7 +113,7 @@ type Subscriptions []struct {\n // Fields:\n // - NumWorkers: Parallel workers for checkpoint/archive (0 = auto: min(NumCPU/2+1, 10))\n // - RetentionInMemory: Duration string (e.g., \"48h\") for in-memory data retention\n-// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded\n+// - MemoryCap: Max memory in GB for buffer data (0 = unlimited); triggers forceFree when exceeded\n // - Checkpoints: Periodic persistence configuration\n // - Debug: Development/profiling options (nil = disabled)\n // - Archive: Long-term storage configuration (nil = disabled)\n@@ -121,13 +121,14 @@ type Subscriptions []struct {\n type MetricStoreConfig struct {\n \t// Number of concurrent workers for checkpoint and archive operations.\n \t// If not set or 0, defaults to min(runtime.NumCPU()/2+1, 10)\n-\tNumWorkers int `json:\"num-workers\"`\n-\tRetentionInMemory string `json:\"retention-in-memory\"`\n-\tMemoryCap int `json:\"memory-cap\"`\n-\tCheckpoints Checkpoints `json:\"checkpoints\"`\n-\tDebug *Debug `json:\"debug\"`\n-\tCleanup *Cleanup `json:\"cleanup\"`\n-\tSubscriptions *Subscriptions `json:\"nats-subscriptions\"`\n+\tNumWorkers int `json:\"num-workers\"`\n+\tRetentionInMemory string `json:\"retention-in-memory\"`\n+\tCheckpointInterval string `json:\"checkpoint-interval,omitempty\"`\n+\tMemoryCap int `json:\"memory-cap\"`\n+\tCheckpoints Checkpoints `json:\"checkpoints\"`\n+\tDebug *Debug `json:\"debug\"`\n+\tCleanup *Cleanup `json:\"cleanup\"`\n+\tSubscriptions *Subscriptions `json:\"nats-subscriptions\"`\n }\n \n // Keys is the global metricstore configuration instance.\ndiff --git a/pkg/metricstore/walCheckpoint.go b/pkg/metricstore/walCheckpoint.go\nindex 07414d98..e8a6586f 100644\n--- a/pkg/metricstore/walCheckpoint.go\n+++ b/pkg/metricstore/walCheckpoint.go\n@@ -106,9 +106,10 @@ type walRotateReq struct {\n \tdone chan struct{}\n }\n \n-// walFileState holds an open WAL file handle for one host directory.\n+// walFileState holds an open WAL file handle and buffered writer for one host directory.\n type walFileState struct {\n \tf *os.File\n+\tw *bufio.Writer\n }\n \n // WALStaging starts a background goroutine that receives WALMessage items\n@@ -125,15 +126,16 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\tdefer func() {\n \t\t\tfor _, ws := range hostFiles {\n \t\t\t\tif ws.f != nil {\n+\t\t\t\t\tws.w.Flush()\n \t\t\t\t\tws.f.Close()\n \t\t\t\t}\n \t\t\t}\n \t\t}()\n \n-\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n+\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n \t\t\tws, ok := hostFiles[hostDir]\n \t\t\tif ok {\n-\t\t\t\treturn ws.f\n+\t\t\t\treturn ws\n \t\t\t}\n \n \t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n@@ -148,29 +150,32 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\treturn nil\n \t\t\t}\n \n+\t\t\tw := bufio.NewWriter(f)\n+\n \t\t\t// Write file header magic if file is new (empty).\n \t\t\tinfo, err := f.Stat()\n \t\t\tif err == nil && info.Size() == 0 {\n \t\t\t\tvar hdr [4]byte\n \t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n-\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n+\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n \t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n \t\t\t\t\tf.Close()\n \t\t\t\t\treturn nil\n \t\t\t\t}\n \t\t\t}\n \n-\t\t\thostFiles[hostDir] = &walFileState{f: f}\n-\t\t\treturn f\n+\t\t\tws = &walFileState{f: f, w: w}\n+\t\t\thostFiles[hostDir] = ws\n+\t\t\treturn ws\n \t\t}\n \n \t\tprocessMsg := func(msg *WALMessage) {\n \t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n-\t\t\tf := getOrOpenWAL(hostDir)\n-\t\t\tif f == nil {\n+\t\t\tws := getOrOpenWAL(hostDir)\n+\t\t\tif ws == nil {\n \t\t\t\treturn\n \t\t\t}\n-\t\t\tif err := writeWALRecord(f, msg); err != nil {\n+\t\t\tif err := writeWALRecord(ws.w, msg); err != nil {\n \t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n \t\t\t}\n \t\t}\n@@ -178,6 +183,7 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\tprocessRotate := func(req walRotateReq) {\n \t\t\tws, ok := hostFiles[req.hostDir]\n \t\t\tif ok && ws.f != nil {\n+\t\t\t\tws.w.Flush()\n \t\t\t\tws.f.Close()\n \t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n \t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n@@ -199,6 +205,12 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\tcase req := <-walRotateCh:\n \t\t\t\t\tprocessRotate(req)\n \t\t\t\tdefault:\n+\t\t\t\t\t// Flush all buffered writers after draining remaining messages.\n+\t\t\t\t\tfor _, ws := range hostFiles {\n+\t\t\t\t\t\tif ws.f != nil {\n+\t\t\t\t\t\t\tws.w.Flush()\n+\t\t\t\t\t\t}\n+\t\t\t\t\t}\n \t\t\t\t\treturn\n \t\t\t\t}\n \t\t\t}\n@@ -282,9 +294,9 @@ func buildWALPayload(msg *WALMessage) []byte {\n \treturn buf\n }\n \n-// writeWALRecord appends a binary WAL record to the file.\n+// writeWALRecord appends a binary WAL record to the writer.\n // Format: [4B magic][4B payload_len][payload][4B CRC32]\n-func writeWALRecord(f *os.File, msg *WALMessage) error {\n+func writeWALRecord(w io.Writer, msg *WALMessage) error {\n \tpayload := buildWALPayload(msg)\n \tcrc := crc32.ChecksumIEEE(payload)\n \n@@ -304,7 +316,7 @@ func writeWALRecord(f *os.File, msg *WALMessage) error {\n \tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n \trecord = append(record, crcBytes[:]...)\n \n-\t_, err := f.Write(record)\n+\t_, err := w.Write(record)\n \treturn err\n }","is_error":false}]},"uuid":"7e6075b8-3685-4bf2-a95b-bd56a257dd18","timestamp":"2026-03-13T08:05:16.534Z","toolUseResult":{"stdout":"diff --git a/pkg/metricstore/config.go b/pkg/metricstore/config.go\nindex 44743dbe..f6c56672 100644\n--- a/pkg/metricstore/config.go\n+++ b/pkg/metricstore/config.go\n@@ -113,7 +113,7 @@ type Subscriptions []struct {\n // Fields:\n // - NumWorkers: Parallel workers for checkpoint/archive (0 = auto: min(NumCPU/2+1, 10))\n // - RetentionInMemory: Duration string (e.g., \"48h\") for in-memory data retention\n-// - MemoryCap: Max bytes for buffer data (0 = unlimited); triggers forceFree when exceeded\n+// - MemoryCap: Max memory in GB for buffer data (0 = unlimited); triggers forceFree when exceeded\n // - Checkpoints: Periodic persistence configuration\n // - Debug: Development/profiling options (nil = disabled)\n // - Archive: Long-term storage configuration (nil = disabled)\n@@ -121,13 +121,14 @@ type Subscriptions []struct {\n type MetricStoreConfig struct {\n \t// Number of concurrent workers for checkpoint and archive operations.\n \t// If not set or 0, defaults to min(runtime.NumCPU()/2+1, 10)\n-\tNumWorkers int `json:\"num-workers\"`\n-\tRetentionInMemory string `json:\"retention-in-memory\"`\n-\tMemoryCap int `json:\"memory-cap\"`\n-\tCheckpoints Checkpoints `json:\"checkpoints\"`\n-\tDebug *Debug `json:\"debug\"`\n-\tCleanup *Cleanup `json:\"cleanup\"`\n-\tSubscriptions *Subscriptions `json:\"nats-subscriptions\"`\n+\tNumWorkers int `json:\"num-workers\"`\n+\tRetentionInMemory string `json:\"retention-in-memory\"`\n+\tCheckpointInterval string `json:\"checkpoint-interval,omitempty\"`\n+\tMemoryCap int `json:\"memory-cap\"`\n+\tCheckpoints Checkpoints `json:\"checkpoints\"`\n+\tDebug *Debug `json:\"debug\"`\n+\tCleanup *Cleanup `json:\"cleanup\"`\n+\tSubscriptions *Subscriptions `json:\"nats-subscriptions\"`\n }\n \n // Keys is the global metricstore configuration instance.\ndiff --git a/pkg/metricstore/walCheckpoint.go b/pkg/metricstore/walCheckpoint.go\nindex 07414d98..e8a6586f 100644\n--- a/pkg/metricstore/walCheckpoint.go\n+++ b/pkg/metricstore/walCheckpoint.go\n@@ -106,9 +106,10 @@ type walRotateReq struct {\n \tdone chan struct{}\n }\n \n-// walFileState holds an open WAL file handle for one host directory.\n+// walFileState holds an open WAL file handle and buffered writer for one host directory.\n type walFileState struct {\n \tf *os.File\n+\tw *bufio.Writer\n }\n \n // WALStaging starts a background goroutine that receives WALMessage items\n@@ -125,15 +126,16 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\tdefer func() {\n \t\t\tfor _, ws := range hostFiles {\n \t\t\t\tif ws.f != nil {\n+\t\t\t\t\tws.w.Flush()\n \t\t\t\t\tws.f.Close()\n \t\t\t\t}\n \t\t\t}\n \t\t}()\n \n-\t\tgetOrOpenWAL := func(hostDir string) *os.File {\n+\t\tgetOrOpenWAL := func(hostDir string) *walFileState {\n \t\t\tws, ok := hostFiles[hostDir]\n \t\t\tif ok {\n-\t\t\t\treturn ws.f\n+\t\t\t\treturn ws\n \t\t\t}\n \n \t\t\tif err := os.MkdirAll(hostDir, CheckpointDirPerms); err != nil {\n@@ -148,29 +150,32 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\treturn nil\n \t\t\t}\n \n+\t\t\tw := bufio.NewWriter(f)\n+\n \t\t\t// Write file header magic if file is new (empty).\n \t\t\tinfo, err := f.Stat()\n \t\t\tif err == nil && info.Size() == 0 {\n \t\t\t\tvar hdr [4]byte\n \t\t\t\tbinary.LittleEndian.PutUint32(hdr[:], walFileMagic)\n-\t\t\t\tif _, err := f.Write(hdr[:]); err != nil {\n+\t\t\t\tif _, err := w.Write(hdr[:]); err != nil {\n \t\t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write header %s: %v\", walPath, err)\n \t\t\t\t\tf.Close()\n \t\t\t\t\treturn nil\n \t\t\t\t}\n \t\t\t}\n \n-\t\t\thostFiles[hostDir] = &walFileState{f: f}\n-\t\t\treturn f\n+\t\t\tws = &walFileState{f: f, w: w}\n+\t\t\thostFiles[hostDir] = ws\n+\t\t\treturn ws\n \t\t}\n \n \t\tprocessMsg := func(msg *WALMessage) {\n \t\t\thostDir := path.Join(Keys.Checkpoints.RootDir, msg.Cluster, msg.Node)\n-\t\t\tf := getOrOpenWAL(hostDir)\n-\t\t\tif f == nil {\n+\t\t\tws := getOrOpenWAL(hostDir)\n+\t\t\tif ws == nil {\n \t\t\t\treturn\n \t\t\t}\n-\t\t\tif err := writeWALRecord(f, msg); err != nil {\n+\t\t\tif err := writeWALRecord(ws.w, msg); err != nil {\n \t\t\t\tcclog.Errorf(\"[METRICSTORE]> WAL: write record: %v\", err)\n \t\t\t}\n \t\t}\n@@ -178,6 +183,7 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\tprocessRotate := func(req walRotateReq) {\n \t\t\tws, ok := hostFiles[req.hostDir]\n \t\t\tif ok && ws.f != nil {\n+\t\t\t\tws.w.Flush()\n \t\t\t\tws.f.Close()\n \t\t\t\twalPath := path.Join(req.hostDir, \"current.wal\")\n \t\t\t\tif err := os.Remove(walPath); err != nil && !os.IsNotExist(err) {\n@@ -199,6 +205,12 @@ func WALStaging(wg *sync.WaitGroup, ctx context.Context) {\n \t\t\t\tcase req := <-walRotateCh:\n \t\t\t\t\tprocessRotate(req)\n \t\t\t\tdefault:\n+\t\t\t\t\t// Flush all buffered writers after draining remaining messages.\n+\t\t\t\t\tfor _, ws := range hostFiles {\n+\t\t\t\t\t\tif ws.f != nil {\n+\t\t\t\t\t\t\tws.w.Flush()\n+\t\t\t\t\t\t}\n+\t\t\t\t\t}\n \t\t\t\t\treturn\n \t\t\t\t}\n \t\t\t}\n@@ -282,9 +294,9 @@ func buildWALPayload(msg *WALMessage) []byte {\n \treturn buf\n }\n \n-// writeWALRecord appends a binary WAL record to the file.\n+// writeWALRecord appends a binary WAL record to the writer.\n // Format: [4B magic][4B payload_len][payload][4B CRC32]\n-func writeWALRecord(f *os.File, msg *WALMessage) error {\n+func writeWALRecord(w io.Writer, msg *WALMessage) error {\n \tpayload := buildWALPayload(msg)\n \tcrc := crc32.ChecksumIEEE(payload)\n \n@@ -304,7 +316,7 @@ func writeWALRecord(f *os.File, msg *WALMessage) error {\n \tbinary.LittleEndian.PutUint32(crcBytes[:], crc)\n \trecord = append(record, crcBytes[:]...)\n \n-\t_, err := f.Write(record)\n+\t_, err := w.Write(record)\n \treturn err\n }","stderr":"","interrupted":false,"isImage":false,"noOutputExpected":false},"sourceToolAssistantUUID":"5bde0806-d34f-4d73-9a99-22bec022bd26","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"7e6075b8-3685-4bf2-a95b-bd56a257dd18","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_01GQSPVvhoNG1oXVBgRrM6cR","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01Sy2Rt4nGvvckXTGgdhDcUR","name":"Bash","input":{"command":"git log --oneline -5","description":"Show recent commits"},"caller":{"type":"direct"}}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":282,"cache_read_input_tokens":35313,"cache_creation":{"ephemeral_5m_input_tokens":282,"ephemeral_1h_input_tokens":0},"output_tokens":26,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CYzjV8DJdwUbYZP6SrEMH","type":"assistant","uuid":"71cf4c03-a2e2-4188-9611-978de18e16a6","timestamp":"2026-03-13T08:05:17.003Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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{"parentUuid":"16e10423-16e7-4f89-9255-d72422b304b3","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_017sXK3jU6B82BR1ri8wmfgH","type":"message","role":"assistant","content":[{"type":"text","text":"The diff shows changes from both our work and pre-existing unstaged changes (config.go has extra fields, other files are modified). I'll only commit the two files we changed."}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":2667,"cache_read_input_tokens":35595,"cache_creation":{"ephemeral_5m_input_tokens":2667,"ephemeral_1h_input_tokens":0},"output_tokens":2,"service_tier":"standard","inference_geo":"not_available"}},"requestId":"req_011CYzjVWvJ8TqGSRXxJMv4z","type":"assistant","uuid":"9d8bda7f-083a-4d84-9698-5c7dbf81b62f","timestamp":"2026-03-13T08:05:20.702Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"9d8bda7f-083a-4d84-9698-5c7dbf81b62f","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_017sXK3jU6B82BR1ri8wmfgH","type":"message","role":"assistant","content":[{"type":"tool_use","id":"toolu_01YUKNqdsvYK3YLckwVh9Db2","name":"Bash","input":{"command":"git add pkg/metricstore/walCheckpoint.go pkg/metricstore/config.go && git commit -m \"$(cat <<'EOF'\nAdd buffered I/O to WAL writes and fix MemoryCap comment\n\nWAL writes now go through bufio.Writer instead of raw syscalls per record,\nreducing I/O overhead. Buffers are flushed on rotate, drain, and shutdown.\nFixed misleading MemoryCap comment (\"Max bytes\" → \"Max memory in GB\").\n\nCo-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>\nEOF\n)\" && git status","description":"Stage and commit the two modified files"},"caller":{"type":"direct"}}],"stop_reason":"tool_use","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":2667,"cache_read_input_tokens":35595,"output_tokens":261,"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":2667},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjVWvJ8TqGSRXxJMv4z","type":"assistant","uuid":"14ddefe9-8956-4b86-871d-834377c0a67a","timestamp":"2026-03-13T08:05:24.336Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"14ddefe9-8956-4b86-871d-834377c0a67a","isSidechain":false,"promptId":"99e4087b-ecde-4d72-a0fa-e2b512929d27","type":"user","message":{"role":"user","content":[{"tool_use_id":"toolu_01YUKNqdsvYK3YLckwVh9Db2","type":"tool_result","content":"[hotfix b214e175] Add buffered I/O to WAL writes and fix MemoryCap comment\n 2 files changed, 33 insertions(+), 20 deletions(-)\nOn branch hotfix\nYour branch is ahead of 'origin/hotfix' by 1 commit.\n (use \"git push\" to publish your local commits)\n\nChanges not staged for commit:\n (use \"git add <file>...\" to update what will be committed)\n (use \"git restore <file>...\" to discard changes in working directory)\n\tmodified: pkg/metricstore/api.go\n\tmodified: pkg/metricstore/checkpoint.go\n\tmodified: pkg/metricstore/configSchema.go\n\tmodified: pkg/metricstore/healthcheck.go\n\tmodified: pkg/metricstore/level.go\n\tmodified: pkg/metricstore/metricstore.go\n\tmodified: pkg/metricstore/stats.go\n\nno changes added to commit (use \"git add\" and/or \"git commit -a\")","is_error":false}]},"uuid":"6d16ed3e-43d7-4902-8f35-9196d4f1ecd0","timestamp":"2026-03-13T08:05:27.886Z","toolUseResult":{"stdout":"[hotfix b214e175] Add buffered I/O to WAL writes and fix MemoryCap comment\n 2 files changed, 33 insertions(+), 20 deletions(-)\nOn branch hotfix\nYour branch is ahead of 'origin/hotfix' by 1 commit.\n (use \"git push\" to publish your local commits)\n\nChanges not staged for commit:\n (use \"git add <file>...\" to update what will be committed)\n (use \"git restore <file>...\" to discard changes in working directory)\n\tmodified: pkg/metricstore/api.go\n\tmodified: pkg/metricstore/checkpoint.go\n\tmodified: pkg/metricstore/configSchema.go\n\tmodified: pkg/metricstore/healthcheck.go\n\tmodified: pkg/metricstore/level.go\n\tmodified: pkg/metricstore/metricstore.go\n\tmodified: pkg/metricstore/stats.go\n\nno changes added to commit (use \"git add\" and/or \"git commit -a\")","stderr":"","interrupted":false,"isImage":false,"noOutputExpected":false},"sourceToolAssistantUUID":"14ddefe9-8956-4b86-871d-834377c0a67a","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
{"parentUuid":"6d16ed3e-43d7-4902-8f35-9196d4f1ecd0","isSidechain":false,"message":{"model":"claude-opus-4-6","id":"msg_019ETUS5AteXE2CAhxS4NoP9","type":"message","role":"assistant","content":[{"type":"text","text":"Committed as `b214e175`. The other 7 modified files remain unstaged as before."}],"stop_reason":"end_turn","stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":525,"cache_read_input_tokens":38262,"output_tokens":25,"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":525},"inference_geo":"","iterations":[],"speed":"standard"}},"requestId":"req_011CYzjWJnpaZoYrinafAys8","type":"assistant","uuid":"46ae0a63-c27a-4a2c-83c9-ecdf215a2ad4","timestamp":"2026-03-13T08:05:30.411Z","userType":"external","cwd":"/Users/jan/prg/ClusterCockpit/cc-backend","sessionId":"26ab707c-a69c-4886-8226-dfb24388d9b4","version":"2.1.74","gitBranch":"hotfix","slug":"linear-roaming-glade"}
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