Sorabh Hamirwasia created LUCENE-9508:
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Summary: DocumentsWriter doesn't check for BlockedFlushes in stall
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Key: LUCENE-9508
URL: https://issues.apache.org/jira/browse/LUCENE-9508
Project: Lucene - Core
Issue Type: Bug
Components: core/index
Affects Versions: 8.5.1
Reporter: Sorabh Hamirwasia
Hi,
I was investigating an issue where the memory usage by a single Lucene
IndexWriter went up to ~23GB. Lucene has a concept of stalling in case the
memory used by each index breaches the 2 X ramBuffer limit (10% of JVM heap,
this case ~3GB). So ideally memory usage should not go above that limit. I
looked into the heap dump and found that the fullFlush thread when enters
*markForFullFlush* method, it tries to take lock on the ThreadStates of all the
DWPT thread sequentially. If lock on one of the ThreadState is blocked then it
will block indefinitely. In this this is what happened as one of the DWPT
thread was stuck in indexing process. Due to this fullFlush thread was unable
to populate the flush queue even though the stall mode was detected. This
caused the new indexing request which came on indexing thread to continue after
sleeping for a second, and continue with indexing. In **preUpdate()** method it
looks for the stalled case and see if there is any pending flushes (based on
flush queue), if not then sleep and continue.
Question:
1) Should **preUpdate** look into the blocked flushes information as well
instead of just flush queue ?
2) Should the fullFlush thread wait indefinitely for the lock on ThreadStates ?
Since single blocking writing thread can block the full flush here.
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