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https://issues.apache.org/jira/browse/LUCENE-10583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17555589#comment-17555589
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Thomas Hoffmann commented on LUCENE-10583:
------------------------------------------
Hello Vigya,
adding the warning to most used classes sounds reasonable.
Another improvement would be to prevent the infinite loop (infinity is always
bad except in math) and add a maximum waiting time with a reasonable default
value.
The exception message when reaching the max. waiting time should include this
hint, not synchronizing with lucene classes.
Thus the programmer might run into this problem but can easily fix it after
reading the message.
Greetings, Thomas
> Deadlock with MMapDirectory while waitForMerges
> -----------------------------------------------
>
> Key: LUCENE-10583
> URL: https://issues.apache.org/jira/browse/LUCENE-10583
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/index
> Affects Versions: 8.11.1
> Environment: Java 17
> OS: Windows 2016
> Reporter: Thomas Hoffmann
> Priority: Minor
> Time Spent: 10m
> Remaining Estimate: 0h
>
> 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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