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https://issues.apache.org/jira/browse/LUCENE-10583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17550072#comment-17550072
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Vigya Sharma commented on LUCENE-10583:
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Thanks for confirming, Thomas.
{quote}no Lucene-Object should be used for synchronization (not just
IndexWriter), right?
I already refactored the class and removed any synchronized-blocks with any
lucene object. This should solve the issue, right?
{quote}
That is correct. Different Lucene objects are internally locked at different
stages, and applications synchronizing on them can lead to deadlocks. Removing
the sync-blocks like you mentioned, should resolve this issue.
> Deadlock with MMapDirectory while waitForMerges
> -----------------------------------------------
>
> Key: LUCENE-10583
> URL: https://issues.apache.org/jira/browse/LUCENE-10583
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/index
> Affects Versions: 8.11.1
> Environment: Java 17
> OS: Windows 2016
> Reporter: Thomas Hoffmann
> Priority: Critical
>
> Hello,
> a deadlock situation happened in our application. We are using MMapDirectory
> on Windows 2016 and got the following stacktrace:
> {code:java}
> "https-openssl-nio-443-exec-30" #166 daemon prio=5 os_prio=0 cpu=78703.13ms
> "https-openssl-nio-443-exec-30" #166 daemon prio=5 os_prio=0 cpu=78703.13ms
> elapsed=81248.18s tid=0x000000002860af10 nid=0x237c in Object.wait()
> [0x00000000413fc000]
> java.lang.Thread.State: TIMED_WAITING (on object monitor)
> at java.lang.Object.wait(java.base@17.0.2/Native Method)
> - waiting on <no object reference available>
> at org.apache.lucene.index.IndexWriter.doWait(IndexWriter.java:4983)
> - locked <0x00000006ef1fc020> (a org.apache.lucene.index.IndexWriter)
> at
> org.apache.lucene.index.IndexWriter.waitForMerges(IndexWriter.java:2697)
> - locked <0x00000006ef1fc020> (a org.apache.lucene.index.IndexWriter)
> at org.apache.lucene.index.IndexWriter.shutdown(IndexWriter.java:1236)
> at org.apache.lucene.index.IndexWriter.close(IndexWriter.java:1278)
> at
> com.speed4trade.ebs.module.search.SearchService.updateSearchIndex(SearchService.java:1723)
> - locked <0x00000006d5c00208> (a org.apache.lucene.store.MMapDirectory)
> at
> com.speed4trade.ebs.module.businessrelations.ticket.TicketChangedListener.postUpdate(TicketChangedListener.java:142)
> ...{code}
> All threads were waiting to lock <0x00000006d5c00208> which got never
> released.
> A lucene thread was also blocked, I dont know if this is relevant:
> {code:java}
> "Lucene Merge Thread #0" #18466 daemon prio=5 os_prio=0 cpu=15.63ms
> elapsed=3499.07s tid=0x00000000459453e0 nid=0x1f8 waiting for monitor entry
> [0x000000005da9e000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at
> org.apache.lucene.store.FSDirectory.deletePendingFiles(FSDirectory.java:346)
> - waiting to lock <0x00000006d5c00208> (a
> org.apache.lucene.store.MMapDirectory)
> at
> org.apache.lucene.store.FSDirectory.maybeDeletePendingFiles(FSDirectory.java:363)
> at org.apache.lucene.store.FSDirectory.createOutput(FSDirectory.java:248)
> at
> org.apache.lucene.store.LockValidatingDirectoryWrapper.createOutput(LockValidatingDirectoryWrapper.java:44)
> at
> org.apache.lucene.index.ConcurrentMergeScheduler$1.createOutput(ConcurrentMergeScheduler.java:289)
> at
> org.apache.lucene.store.TrackingDirectoryWrapper.createOutput(TrackingDirectoryWrapper.java:43)
> at
> org.apache.lucene.codecs.compressing.CompressingStoredFieldsWriter.<init>(CompressingStoredFieldsWriter.java:121)
> at
> org.apache.lucene.codecs.compressing.CompressingStoredFieldsFormat.fieldsWriter(CompressingStoredFieldsFormat.java:130)
> at
> org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat.fieldsWriter(Lucene87StoredFieldsFormat.java:141)
> at
> org.apache.lucene.index.SegmentMerger.mergeFields(SegmentMerger.java:227)
> at org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:105)
> at org.apache.lucene.index.IndexWriter.mergeMiddle(IndexWriter.java:4757)
> at org.apache.lucene.index.IndexWriter.merge(IndexWriter.java:4361)
> at
> org.apache.lucene.index.IndexWriter$IndexWriterMergeSource.merge(IndexWriter.java:5920)
> at
> org.apache.lucene.index.ConcurrentMergeScheduler.doMerge(ConcurrentMergeScheduler.java:626)
> at
> org.apache.lucene.index.ConcurrentMergeScheduler$MergeThread.run(ConcurrentMergeScheduler.java:684){code}
> If looks like the merge operation never finished and released the lock.
> Is there any option to prevent this deadlock or how to investigate it further?
> A load-test didn't show this problem unfortunately.
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