Jaroslaw Grabowski created CASSANDRA-15880:
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Summary: 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
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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