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https://issues.apache.org/jira/browse/OAK-2570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14346647#comment-14346647
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Michael Dürig commented on OAK-2570:
------------------------------------
bq. Can you review the usage around BackgroundObserver.
Looks good AFAICS.
bq. so if content changes are collapsed that should be fine
Diffs across multiple revisions might be more expensive to execute though. So
having a bit of a queue can't harm I think.
> Open indexes in IndexTracker non blocking way
> ---------------------------------------------
>
> Key: OAK-2570
> URL: https://issues.apache.org/jira/browse/OAK-2570
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: oak-lucene
> Reporter: Chetan Mehrotra
> Assignee: Chetan Mehrotra
> Fix For: 1.2, 1.0.13
>
> Attachments: OAK-2570.patch
>
>
> Currently {{IndexTracker}} opens the indexes in same thread where the commit
> happens as it acts as an {{Observer}}. If opening the index takes long time
> it would block the commit thread and might introduce delay in other operation
> on same thread.
> For example {{DocumentNodeStore}} invokes the {{Observer}} in
> {{backgroundRead}} and that call would not complete unless the {{Observer}}
> returns back. For a system to be responsive the {{backgroundRead}} has to be
> quick as it holds the write lock. Due to current implementation at time
> system turn unresponsive.
> Looking at the threaddump from one such unresponsive system it appears that
> slowness is due to Lucene index taking time to reopen.
> Thread which hold the {{backgroundOperationLock}} for {{read}} is
> {noformat}
> "pool-9-thread-1" Id=101 in RUNNABLE
> at java.io.FileInputStream.open(Native Method)
> at java.io.FileInputStream.<init>(FileInputStream.java:146)
> at
> org.apache.jackrabbit.core.data.LazyFileInputStream.open(LazyFileInputStream.java:104)
> at
> org.apache.jackrabbit.core.data.LazyFileInputStream.read(LazyFileInputStream.java:163)
> at com.google.common.io.ByteStreams.read(ByteStreams.java:828)
> at com.google.common.io.ByteStreams.readFully(ByteStreams.java:695)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.OakDirectory$OakIndexFile.loadBlob(OakDirectory.java:218)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.OakDirectory$OakIndexFile.readBytes(OakDirectory.java:264)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.OakDirectory$OakIndexInput.readBytes(OakDirectory.java:350)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.OakDirectory$OakIndexInput.readByte(OakDirectory.java:356)
> at org.apache.lucene.store.DataInput.readInt(DataInput.java:84)
> at org.apache.lucene.codecs.CodecUtil.checkHeader(CodecUtil.java:126)
> at org.apache.lucene.util.fst.FST.<init>(FST.java:318)
> at org.apache.lucene.util.fst.FST.<init>(FST.java:304)
> at
> org.apache.lucene.codecs.BlockTreeTermsReader$FieldReader.<init>(BlockTreeTermsReader.java:484)
> at
> org.apache.lucene.codecs.BlockTreeTermsReader.<init>(BlockTreeTermsReader.java:176)
> at
> org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat.fieldsProducer(Lucene41PostingsFormat.java:437)
> at
> org.apache.lucene.index.SegmentCoreReaders.<init>(SegmentCoreReaders.java:116)
> at org.apache.lucene.index.SegmentReader.<init>(SegmentReader.java:96)
> at
> org.apache.lucene.index.StandardDirectoryReader$1.doBody(StandardDirectoryReader.java:62)
> at
> org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(SegmentInfos.java:843)
> at
> org.apache.lucene.index.StandardDirectoryReader.open(StandardDirectoryReader.java:52)
> at org.apache.lucene.index.DirectoryReader.open(DirectoryReader.java:66)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.IndexNode.<init>(IndexNode.java:94)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.IndexNode.open(IndexNode.java:62)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker$1.leave(IndexTracker.java:96)
> at
> org.apache.jackrabbit.oak.spi.commit.EditorDiff.childNodeChanged(EditorDiff.java:153)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.dispatch(DocumentNodeState.java:433)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.compareAgainstBaseState(DocumentNodeState.java:260)
> at
> org.apache.jackrabbit.oak.spi.commit.EditorDiff.childNodeChanged(EditorDiff.java:148)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.dispatch(DocumentNodeState.java:433)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.compareAgainstBaseState(DocumentNodeState.java:260)
> at
> org.apache.jackrabbit.oak.spi.commit.EditorDiff.process(EditorDiff.java:52)
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker.update(IndexTracker.java:105)
> - locked
> org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker@6243264e
> at
> org.apache.jackrabbit.oak.plugins.index.lucene.LuceneIndexProvider.contentChanged(LuceneIndexProvider.java:61)
> at
> org.apache.jackrabbit.oak.spi.commit.CompositeObserver.contentChanged(CompositeObserver.java:53)
> - locked org.apache.jackrabbit.oak.spi.commit.CompositeObserver@2687fd48
> at
> org.apache.jackrabbit.oak.spi.commit.ChangeDispatcher.contentChanged(ChangeDispatcher.java:79)
> - locked org.apache.jackrabbit.oak.spi.commit.ChangeDispatcher@2a0595bb
> at
> org.apache.jackrabbit.oak.plugins.document.CommitQueue.afterTrunkCommit(CommitQueue.java:131)
> - locked org.apache.jackrabbit.oak.plugins.document.CommitQueue@54a93d8a
> at
> org.apache.jackrabbit.oak.plugins.document.CommitQueue.done(CommitQueue.java:83)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.done(DocumentNodeStore.java:586)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.persist(DocumentNodeStoreBranch.java:187)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.persist(DocumentNodeStoreBranch.java:91)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.persist(DocumentNodeStoreBranch.java:39)
> at
> org.apache.jackrabbit.oak.spi.state.AbstractNodeStoreBranch$InMemory.merge(AbstractNodeStoreBranch.java:525)
> at
> org.apache.jackrabbit.oak.spi.state.AbstractNodeStoreBranch.merge(AbstractNodeStoreBranch.java:318)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.merge(DocumentNodeStoreBranch.java:135)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentRootBuilder.merge(DocumentRootBuilder.java:159)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.merge(DocumentNodeStore.java:1339)
> at
> org.apache.jackrabbit.oak.plugins.index.AsyncIndexUpdate.mergeWithConcurrencyCheck(AsyncIndexUpdate.java:420)
> at
> org.apache.jackrabbit.oak.plugins.index.AsyncIndexUpdate.updateIndex(AsyncIndexUpdate.java:389)
> at
> org.apache.jackrabbit.oak.plugins.index.AsyncIndexUpdate.run(AsyncIndexUpdate.java:300)
> - locked
> org.apache.jackrabbit.oak.plugins.index.AsyncIndexUpdate@401daa3f
> at
> org.apache.sling.commons.scheduler.impl.QuartzJobExecutor.execute(QuartzJobExecutor.java:105)
> at org.quartz.core.JobRunShell.run(JobRunShell.java:207)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> Further {{DocumentNodeStore background thread}} is also waiting to acquire
> the write lock
> {noformat}
> "DocumentNodeStore background thread" Id=82 in WAITING on
> lock=java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync@6990d994
> at sun.misc.Unsafe.park(Native Method)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:867)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1197)
> at
> java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:945)
> at
> org.apache.jackrabbit.oak.plugins.document.UnsavedModifications.persist(UnsavedModifications.java:156)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.backgroundWrite(DocumentNodeStore.java:1662)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.runBackgroundOperations(DocumentNodeStore.java:1456)
> - locked
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore@350b4c49
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore$BackgroundOperation.execute(DocumentNodeStore.java:2064)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore$NodeStoreTask.run(DocumentNodeStore.java:2039)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> Now as javadoc of {{ReentrantReadWriteLock}} the readLock would not be
> granted if there is a waiter for write lock. Hence in such a case no further
> reads would be possible and system would not respond well
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