The cache fsynced every payload and manifest -- two per entry, ~18 ms, and a
push publishes one entry per question (~22,000 on a WordPress plugin). A
read already rejects any entry whose manifest receipt, payload size or
payload SHA-256 does not check, so a torn write is a miss, never a wrong
answer; the fsyncs bought nothing the verification does not.
The broader problem: three quadratic walls in this replay were found one
per two-hour run, because all were Python bookkeeping between engine calls
and the only record was the engine log. `OUSAST_SAMPLE_PROFILE=<path>`
starts an in-process sampler that rewrites the hottest stacks every 30 s,
so a run killed at its deadline still names where its time went. The host
cannot ptrace the container, hence in-process. The replay harness turns it
on per case.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo
The real cause of the 13.3 replay wall. Every cache publication called
`_make_room`, which listed and stat'ed every entry to total the cache size,
and a push publishes one answer per question -- 22,125 on a WordPress
plugin. Measured on the live replay cache: one scan 0.68 s at 12,238
entries, ~70 minutes spent scanning by then, ~2.3 hours to finish the
evidence pass. The engine was idle while the Python process sat at 83% CPU;
the 13/31/51-minute portions were the quadratic growing.
The scan is now remembered, keyed by the cache root's modification stamp:
our own publications and evictions update the tally in place, and any
change another process makes moves the stamp and forces a rescan, so the
size limit stays exact under concurrent pushes. Lock stripes are created up
front so their first use never invalidates the tally. Eviction order and
lease handling are unchanged.
Controls: 61 publications (one a same-key replacement) take exactly one
scan and the tally equals a fresh scan; a second writer on the same root
forces a rescan and the limit holds.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo
