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https://issues.apache.org/jira/browse/CASSANDRA-21657?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Semb Wever updated CASSANDRA-21657:
-------------------------------------------
Test and Documentation Plan:
The new HintsWriteExecutorTest (1 test) passes on JDK 17, and fails with
"262144 bytes of direct memory are still held" when only the release is removed.
The test reads the direct buffer pool through BufferPoolMXBean, builds a
HintsWriteExecutor, holds that the pool grew by at least WRITE_BUFFER_SIZE, and
then holds that the shutdown gives that memory back.
HintsServiceTest (4 tests) passes.
Status: Patch Available (was: Open)
> The hints write buffer is not released when the write executor shuts down
> -------------------------------------------------------------------------
>
> Key: CASSANDRA-21657
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21657
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Consistency/Hints
> Reporter: Michael Semb Wever
> Priority: Normal
> Fix For: 5.0.x, 6.0.x, 7.x
>
>
> {{HintsWriteExecutor}} allocates a 256 KiB direct buffer that every write
> task shares:
> {code:java}
> writeBuffer = ByteBuffer.allocateDirect(WRITE_BUFFER_SIZE);
> {code}
> {{shutdownBlocking}} shuts the executor down and leaves the buffer allocated.
> A process that shuts the hints service down and starts it again loses 256 KiB
> of direct memory each time. The in-JVM test framework does exactly that, once
> per instance restart, so a long dtest run holds direct memory that no
> instance can use.
> A node shutdown in production ends the process, so the priority is Low; the
> cost falls on the test framework and on any other caller that restarts the
> service in one process.
> The patch releases the buffer with {{FileUtils.clean}} after the executor
> terminates. The release waits for termination, because a write task that
> still runs holds the buffer, and a shutdown that gives up after its minute
> reports the buffer it keeps rather than freeing memory a task may write to.
> Patch:
> [mck/upstream/hints-write-buffer-release/5.0|https://github.com/thelastpickle/cassandra/tree/mck/upstream/hints-write-buffer-release/5.0]
> Provenance:
> [00003d27fa|https://github.com/datastax/cassandra/commit/00003d27faf2241245436d9440d740e1cd18aaa8]
> by [~jlewandowski]. That commit releases the buffer in a {{finally}} block
> and carries further work on the buffer pool and on the in-JVM instance
> shutdown, which this patch leaves out. The {{finally}} block frees the buffer
> even when a write task is still running, so this patch tests the termination
> result instead, and adds the regression test the commit lacks.
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