Details
-
Bug
-
Status: Open
-
Minor
-
Resolution: Unresolved
-
5.5.2, 6.2
-
None
-
None
-
New
Description
separated out from https://issues.apache.org/jira/browse/LUCENE-2585
I've seen race condition diagnostics for Lucene code that could be related to this. Line numbers are for Lucene 5.5.2, but the problem seems present in master too.
AFAICT: StandardDirectoryReader has an IndexWriter, and it checks things are up-to-date by checking if there are pending in-memory updates by looking at IndexWriter.SegmentInfos.version. That read is not synchronized relative to its write from IndexWriter.updateDocument
I'm not enough of a lucene expert to suggest how to fix this in detail. If I would guess at how Lucene roughly works, I would suggest the following
- when applying pending in-memory changes, this takes a lock, and under lock there is a "changed = true" assignment.
- when checking for changes, take lock, return changed.
- when writing pending in-memory changes, take lock, write out file, set "changed=false", release lock.
The problem can be reproduced by running some of the Gerrit acceptance tests under Threadsanitizer. I don't know of open-source tooling to set that up, unfortunately.
WARNING: ThreadSanitizer: data race (pid=21636)
Write of size 8 at 0x7f24ad9d3210 by thread T36 (mutexes: write M431922409782456832):
#0 org.apache.lucene.index.SegmentInfos.changed()V (SegmentInfos.java:944)
#1 org.apache.lucene.index.IndexWriter.newSegmentName()Ljava/lang/String; (IndexWriter.java:1652)
#2 org.apache.lucene.index.DocumentsWriter.ensureInitialized(Lorg/apache/lucene/index/DocumentsWriterPerThreadPool$ThreadState;)V (DocumentsWriter.java:391)
#3 org.apache.lucene.index.DocumentsWriter.updateDocument(Ljava/lang/Iterable;Lorg/apache/lucene/analysis/Analyzer;Lorg/apache/lucene/index/Term;)Z (DocumentsWriter.java:445)
#4 org.apache.lucene.index.IndexWriter.updateDocument(Lorg/apache/lucene/index/Term;Ljava/lang/Iterable;)V (IndexWriter.java:1477)
#5 com.google.gerrit.lucene.AutoCommitWriter.updateDocument(Lorg/apache/lucene/index/Term;Ljava/lang/Iterable;)V (AutoCommitWriter.java:100)
#6 org.apache.lucene.index.TrackingIndexWriter.updateDocument(Lorg/apache/lucene/index/Term;Ljava/lang/Iterable;)J (TrackingIndexWriter.java:55)
#7 com.google.gerrit.lucene.AbstractLuceneIndex$4.call()Ljava/lang/Long; (AbstractLuceneIndex.java:250)
#8 com.google.gerrit.lucene.AbstractLuceneIndex$4.call()Ljava/lang/Object; (AbstractLuceneIndex.java:247)
#9 com.google.common.util.concurrent.TrustedListenableFutureTask$TrustedFutureInterruptibleTask.runInterruptibly()V (TrustedListenableFutureTask.java:108)
#10 com.google.common.util.concurrent.InterruptibleTask.run()V (InterruptibleTask.java:41)
#11 com.google.common.util.concurrent.TrustedListenableFutureTask.run()V (TrustedListenableFutureTask.java:77)
#12 java.util.concurrent.ThreadPoolExecutor.runWorker(Ljava/util/concurrent/ThreadPoolExecutor$Worker;)V (ThreadPoolExecutor.java:1142)
#13 java.util.concurrent.ThreadPoolExecutor$Worker.run()V (ThreadPoolExecutor.java:617)
#14 java.lang.Thread.run()V (Thread.java:745)
#15 (Generated Stub)
Previous read of size 8 at 0x7f24ad9d3210 by thread T29 (mutexes: write M1060737507754061632):
#0 org.apache.lucene.index.IndexWriter.nrtIsCurrent(Lorg/apache/lucene/index/SegmentInfos;)Z (IndexWriter.java:4592)
#1 org.apache.lucene.index.StandardDirectoryReader.doOpenFromWriter(Lorg/apache/lucene/index/IndexCommit;)Lorg/apache/lucene/index/DirectoryReader; (StandardDirectoryReader.java:282)
#2 org.apache.lucene.index.StandardDirectoryReader.doOpenIfChanged(Lorg/apache/lucene/index/IndexCommit;)Lorg/apache/lucene/index/DirectoryReader; (StandardDirectoryReader.java:261)
#3 org.apache.lucene.index.StandardDirectoryReader.doOpenIfChanged()Lorg/apache/lucene/index/DirectoryReader; (StandardDirectoryReader.java:251)
#4 org.apache.lucene.index.DirectoryReader.openIfChanged(Lorg/apache/lucene/index/DirectoryReader;)Lorg/apache/lucene/index/DirectoryReader; (DirectoryReader.java:137)
#5 com.google.gerrit.lucene.WrappableSearcherManager.refreshIfNeeded(Lorg/apache/lucene/search/IndexSearcher;)Lorg/apache/lucene/search/IndexSearcher; (WrappableSearcherManager.java:148)
#6 com.google.gerrit.lucene.WrappableSearcherManager.refreshIfNeeded(Ljava/lang/Object;)Ljava/lang/Object; (WrappableSearcherManager.java:68)
#7 org.apache.lucene.search.ReferenceManager.doMaybeRefresh()V (ReferenceManager.java:176)
#8 org.apache.lucene.search.ReferenceManager.maybeRefreshBlocking()V (ReferenceManager.java:253)
#9 org.apache.lucene.search.ControlledRealTimeReopenThread.run()V (ControlledRealTimeReopenThread.java:245)
#10 (Generated Stub)