Checkpoint: bf29af79b268

Entire-Session: 0943a044-b17e-4215-8591-c1a0c816ddf0
Entire-Strategy: manual-commit
Entire-Agent: Claude Code
Ephemeral-branch: entire/02f82c2-e3b0c4

bf/29af79b268/0/content_hash.txt

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+sha256:b184f713fed8a0efc8240d19849de07ab8e1009e71da3ce0891e3f282cf69adb

bf/29af79b268/0/context.md

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+# Session Context
+
+## User Prompts
+
+### Prompt 1
+
+Implement the following plan:
+
+# Fix: Memory Escalation in flattenCheckpointFile (68GB+)
+
+## Context
+
+Production gops shows `flattenCheckpointFile` allocating 68GB+ (74.89% of memory). The archiving pipeline accumulates ALL metric data from ALL hosts into a single `[]ParquetMetricRow` slice before writing to Parquet. For large HPC clusters this is catastrophic. Additionally, the `SortingWriterConfig` in the parquet writer buffers everything again internally.
+
+## Root Cause
+
+Two-layer unbounde...
+
+### Prompt 2
+
+Are the any other cases with memory spikes using the Parquet Writer, e.g. in the nodestate retention?
+
+### Prompt 3
+
+[Request interrupted by user for tool use]
+
+### Prompt 4
+
+Compare the archive writer implementation with @~/tmp/cc-backend/pkg/metricstore/parquetArchive.go . Compare and explain differences.
+
+### Prompt 5
+
+Add an Info logmessage in archiveCheckpoints that archving started and provide timing information how long it took.
+

bf/29af79b268/0/metadata.json

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+  "created_at": "2026-03-18T04:22:41.042241Z",
+  "branch": "hotfix",
+  "checkpoints_count": 2,
+  "files_touched": [
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+    "agent_percentage": 100
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+}

bf/29af79b268/0/prompt.txt

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+Implement the following plan:
+
+# Fix: Memory Escalation in flattenCheckpointFile (68GB+)
+
+## Context
+
+Production gops shows `flattenCheckpointFile` allocating 68GB+ (74.89% of memory). The archiving pipeline accumulates ALL metric data from ALL hosts into a single `[]ParquetMetricRow` slice before writing to Parquet. For large HPC clusters this is catastrophic. Additionally, the `SortingWriterConfig` in the parquet writer buffers everything again internally.
+
+## Root Cause
+
+Two-layer unbounded accumulation:
+
+1. **`archive.go:239-242`**: `allRows = append(allRows, r.rows...)` merges every host's rows into one giant slice
+2. **`parquetArchive.go:108-116`**: `SortingWriterConfig` creates a sorting writer that buffers ALL rows until `Close()`
+3. **`parquetArchive.go:199`**: `var rows []ParquetMetricRow` starts at zero capacity, grows via append doubling
+
+Peak memory = (all hosts' rows) + (sorting writer copy) + (append overhead) = ~3x raw data size.
+
+## Fix: Stream per-host to parquet writer
+
+Instead of accumulating all rows, write each host's data as a separate row group.
+
+### Step 1: Add streaming parquet writer (`parquetArchive.go`)
+
+Replace `writeParquetArchive(filename, rows)` with a struct that supports incremental writes:
+
+```go
+type parquetArchiveWriter struct {
+    writer *pq.GenericWriter[ParquetMetricRow]
+    bw     *bufio.Writer
+    f      *os.File
+    count  int
+}
+
+func newParquetArchiveWriter(filename string) (*parquetArchiveWriter, error)
+func (w *parquetArchiveWriter) WriteHostRows(rows []ParquetMetricRow) error  // Write + Flush (creates row group)
+func (w *parquetArchiveWriter) Close() error
+```
+
+- **Remove `SortingWriterConfig`** - no global sort buffer
+- Sort each host's rows in-place with `sort.Slice` before writing (cheap: single host data)
+- Each `Flush()` creates a separate row group per host
+
+### Step 2: Add row count estimation (`parquetArchive.go`)
+
+```go
+func estimateRowCount(cf *CheckpointFile) int
+```
+
+Pre-allocate `rows` slice in `archiveCheckpointsToParquet` to avoid append doubling per host.
+
+### Step 3: Restructure `archiveCheckpoints` (`archive.go`)
+
+Change from:
+```
+workers → channel → accumulate allRows → writeParquetArchive(allRows)
+```
+
+To:
+```
+open writer → workers → channel → for each host: sort rows, writer.WriteHostRows(rows) → close writer
+```
+
+- Only one host's rows in memory at a time
+- Track `files`/`dir` for deletion separately (don't retain rows)
+- Check `writer.count > 0` instead of `len(allRows) == 0`
+
+### Step 4: Update test (`parquetArchive_test.go`)
+
+- `TestParquetArchiveRoundtrip`: use new streaming writer API
+- Keep `archiveCheckpointsToParquet` returning rows (it's per-host, manageable size)
+
+## Files to Modify
+
+- **`pkg/metricstore/parquetArchive.go`**: Add `parquetArchiveWriter`, `estimateRowCount`; remove `writeParquetArchive`; add `"sort"` import
+- **`pkg/metricstore/archive.go`**: Restructure `archiveCheckpoints` to stream
+- **`pkg/metricstore/parquetArchive_test.go`**: Update roundtrip test
+
+## Memory Impact
+
+- **Before**: All hosts in memory (~40GB for 256 nodes) + sorting buffer (~40GB) = 68GB+
+- **After**: One host at a time (~16MB) + parquet page buffer (~1MB) = ~17MB peak
+
+## Sorting Tradeoff
+
+The output changes from one globally-sorted row group to N row groups (one per host), each internally sorted by (metric, timestamp). This is actually better for ClusterCockpit's per-host query patterns (enables row group skipping).
+
+## Verification
+
+```bash
+go test -v ./pkg/metricstore/...
+```
+
+Also verify with `go vet ./pkg/metricstore/...` for correctness.
+
+
+If 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-CC-cc-backend/71340843-de3d-4e83-9dcb-2fc130c50e0d.jsonl
+
+---
+
+Are the any other cases with memory spikes using the Parquet Writer, e.g. in the nodestate retention?
+
+---
+
+[Request interrupted by user for tool use]
+
+---
+
+Compare the archive writer implementation with @~/tmp/cc-backend/pkg/metricstore/parquetArchive.go . Compare and explain differences.
+
+---
+
+Add an Info logmessage in archiveCheckpoints that archving started and provide timing information how long it took.

bf/29af79b268/metadata.json

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+{
+  "cli_version": "0.4.8",
+  "checkpoint_id": "bf29af79b268",
+  "strategy": "manual-commit",
+  "branch": "hotfix",
+  "checkpoints_count": 2,
+  "files_touched": [
+    "pkg/metricstore/archive.go"
+  ],
+  "sessions": [
+    {
+      "metadata": "/bf/29af79b268/0/metadata.json",
+      "transcript": "/bf/29af79b268/0/full.jsonl",
+      "context": "/bf/29af79b268/0/context.md",
+      "content_hash": "/bf/29af79b268/0/content_hash.txt",
+      "prompt": "/bf/29af79b268/0/prompt.txt"
+    }
+  ],
+  "token_usage": {
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+    "api_call_count": 28
+  }
+}