codenotary / immudb / 28225094361

85%

master: 85%

Build Type

Pull #2104

gh-ci

Committed by vchaindz

Commit Message

fix(multiapp): serve ReadAt from a detached handle on cache eviction race

A foreground ReadAt cache-miss opens and caches a chunk via singleflight,
then re-acquires it from the cache to take its ref. A concurrent insert
(another foreground miss or a background prefetch) could evict or replace
that just-inserted entry in between, so the re-acquire returned
cache.ErrKeyNotFound and ReadAt failed with a spurious "key not found"
for a perfectly valid, readable offset.

This surfaced as flaky failures in
embedded/appendable/remoteapp.TestWritePastFirstChunk (~3/8 full-package
runs), introduced by the parallel-prefetch / range-fetch read path.

Fix: when the post-open re-acquire misses, the data is still readable, so
re-open a detached, self-closing handle (refs=1, evicted) for that single
read instead of erroring. The detached handle is released exactly once by
ReadAt, which performs the underlying Close, so there is no leak.

Adds TestMultiAppConcurrentReadEvictionRace, which deterministically
reproduces the race (small cache + prefetch + concurrent sequential
readers) — 10/10 "key not found" before the fix, 0/20 after, clean under
-race.

Pull Request Pull Request #2104: fix(multiapp): serve ReadAt from a detached handle on cache eviction race

Coverage Stats

14 of 17 new or added lines in 2 files covered. (82.35%)

3 existing lines in 1 file now uncovered.

45240 of 53234 relevant lines covered (84.98%)

126722.38 hits per line