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Reading a snapshot that was already purged makes the cache loader fail with FILE_NOT_FOUND, so no cache entry is created, yet the gauge was still incremented. Every decrement requires a cached entry, so each such read left the gauge permanently one higher than the real cache size.
rjgoyln
marked this pull request as ready for review
October 3, 2026 17:27
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What changes were proposed in this pull request?
Reading a snapshot that has already been purged makes the cache loader fail with
FILE_NOT_FOUND.SnapshotCache.getcreates no cache entry in that case, yet still incrementedNumSnapshotCacheSize. Both decrements require an entry, so each such read left the JMX gauge one higher than the real cache size for good.The gauge is now incremented only once the loader returns a snapshot.
What is the link to the Apache JIRA
https://issues.apache.org/jira/browse/HDDS-16694
How was this patch tested?
The new
TestSnapshotCache#testGetInactiveSnapshotDoesNotIncrementCacheSizefails on master (expected: <0> but was: <1>) and passes with the change; the other 27 tests in the class still pass.Generated-by: Claude Code (Opus 5.5)