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Posted to commits@cassandra.apache.org by "Berenguer Blasi (Jira)" <ji...@apache.org> on 2020/10/02 10:16:00 UTC
[jira] [Commented] (CASSANDRA-15880) Memory leak in
CompressedChunkReader
[ https://issues.apache.org/jira/browse/CASSANDRA-15880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17206084#comment-17206084 ]
Berenguer Blasi commented on CASSANDRA-15880:
---------------------------------------------
4.0 PR squashed, 3.11 PR ready and tests results attached to the PR.
> Memory leak in CompressedChunkReader
> ------------------------------------
>
> Key: CASSANDRA-15880
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15880
> Project: Cassandra
> Issue Type: Bug
> Components: Feature/Compression
> Reporter: Jaroslaw Grabowski
> Assignee: Berenguer Blasi
> Priority: Normal
> Fix For: 4.0, 3.11.x, 4.0-triage
>
> Time Spent: 6h
> Remaining Estimate: 0h
>
> CompressedChunkReader uses java.lang.ThreadLocal to reuse ByteBuffer for compressed data. ByteBuffers leak due to peculiar ThreadLocal quality.
> ThreadLocals are stored in a map, where the key is a weak reference to a ThreadLocal and the value is the user's object (ByteBuffer in this case). When a last strong reference to a ThreadLocal is lost, weak reference to ThreadLocal (key) is removed but the value (ByteBuffer) is kept until cleaned by ThreadLocal heuristic expunge mechanism. See ThreadLocal's "stale entries" for details.
> When a number of long-living threads is high enough this results in thousands of ByteBuffers stored as stale entries in ThreadLocals. In a not-so-lucky scenario we get OutOfMemoryException.
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