David Snelling
bc70c43d02
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Every log-authority open asks the fact log one question — is there a fact
above the committed pointer? — and answered it by reading and CRC-decoding
EVERY segment file the manifest names. MEASURED in production on a 16k-row
brain at generation ~478,819: 34-37 seconds inside `generation-store-open-fold`
on every open, including the clean one where the answer is always "nothing".
The manifest already knows. A sealed segment's `lastGeneration` is written at
seal time, and the seal order has been the same since the log was introduced:
`rotate()` fsyncs the tail's bytes FIRST ("sealed segments are always fully
durable"), builds the entry from the content that fsync covered, and only then
flips the manifest — atomically, fsynced, and in the same write re-pointing
`tailSegment`, so a sealed file is never appended to again. A crash in that
order is safe in the pruning direction: before the manifest write the segment
is still the TAIL and is read whole; after it, the entry describes bytes that
were already durable. The only later mutation of a sealed segment is open()'s
straddle truncation, which removes facts and re-derives the entry from the
actual bytes — a recorded bound can drift DOWN with its file, never up.
So `lastGeneration = L` proves the file holds no fact above L, and both
manifest-direct passes (`peekFactsAbove` and its streaming twin, the recovery
fold) now read only the unsealed tail, entries with no numeric
`lastGeneration` — legacy or hand-repaired manifests, never prune what you
cannot prove — and entries whose recorded maximum is actually above the bound.
The open narrates what it read and what it pruned when the log holds more than
one segment.
Pinned in tests/integration/factlog-open-prune.test.ts, from the log's own
counters rather than a clock: a clean reopen over five sealed segments reads
exactly the tail (1 of 6) and finds nothing; a real SIGKILLed writer that
sealed segments holding facts above the committed pointer has those segments
READ, and its peek, its fold stream and its rollback all match the unpruned
full scan fact for fact; a manifest entry missing `lastGeneration` is read.
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| .. | ||
| api | ||
| benchmarks | ||
| comprehensive | ||
| configs | ||
| conformance | ||
| fixtures | ||
| helpers | ||
| integration | ||
| integrations | ||
| lifecycle | ||
| performance | ||
| regression | ||
| scripts | ||
| transaction | ||
| unit | ||
| vfs | ||
| critical-neural-validation.test.ts | ||
| critical-performance-benchmark.test.ts | ||
| model-loading.test.ts | ||
| package-size-breakdown.test.ts | ||
| package-size-limit.test.ts | ||
| setup-integration.ts | ||
| setup-semantic.ts | ||
| setup-unit.ts | ||
| setup.ts | ||
| type-utils.unit.test.ts | ||