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https://issues.apache.org/jira/browse/CASSANDRA-15880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17191949#comment-17191949
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Berenguer Blasi edited comment on CASSANDRA-15880 at 9/8/20, 5:33 AM:
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Note for the reviewer: {{CompressedChunkReader.Standard}} is a
{{RebuffererFactory}} where the main method at use is
{{CompressedChunkReader.instantiateRebufferer()}}. That one wraps the reader in
a {{BufferManagingRebufferer}} which will call {{close()}} and it's
{{AutoClosable}} also. I have checked for uses of the reader in the code and as
expected it is being closed/auto closed so I expect the {{ThreadLocal}} to be
properly removed and not leak now.
was (Author: bereng):
Note for the reviewer: {{CompressedChunkReader.Standard}} is a
{{RebuffererFactory}} where the main method at use is
{{CompressedChunkReader.instantiateRebufferer()}}. That one wraps the reader in
a {{BufferManagingRebufferer}} which will call {{close()}} and also is
{{AutoClosable}}. I have checked for uses of the reader in the code and as
expected it is being closed/auto closed so I expect the {{ThreadLocal}} to be
properly removed and not leak now.
> 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
>
> Time Spent: 10m
> 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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