We have seen the following stack trace, and saw that fsync was seemingly very slow on the system.
Two issues: (1) fsync seems to be very slow here (2) fsync is called while holding a lock.
(2) should be resolved by lazy-loading indexes.
"oak-lucene-22" daemon prio=1 tid=0x6b1 nid=0xffffffff runnable java.lang.Thread.State: RUNNABLE atjava.io.FileDescriptor.sync(Native Method) at org.apache.lucene.store.FSDirectory.fsync(FSDirectory.java:505) at org.apache.lucene.store.FSDirectory.sync(FSDirectory.java:307) at org.apache.lucene.store.NRTCachingDirectory.sync(NRTCachingDirectory.java:219) at org.apache.lucene.index.IndexWriter.startCommit(IndexWriter.java:4489) at org.apache.lucene.index.IndexWriter.prepareCommitInternal(IndexWriter.java:2953) - locked <0x20595abf> (a java.lang.Object) at org.apache.lucene.index.IndexWriter.commitInternal(IndexWriter.java:3049) - locked <0x20595abf> (a java.lang.Object) at org.apache.lucene.index.IndexWriter.closeInternal(IndexWriter.java:1041) at org.apache.lucene.index.IndexWriter.close(IndexWriter.java:932) - locked <0x20595abf> (a java.lang.Object) at org.apache.lucene.index.IndexWriter.close(IndexWriter.java:894) at org.apache.jackrabbit.oak.plugins.index.lucene.hybrid.NRTIndex.close(NRTIndex.java:206) at org.apache.jackrabbit.oak.plugins.index.lucene.hybrid.NRTIndexFactory.closeLast(NRTIndexFactory.java:133) at org.apache.jackrabbit.oak.plugins.index.lucene.hybrid.NRTIndexFactory.createIndex(NRTIndexFactory.java:89) - locked <0x85f9b65> (a org.apache.jackrabbit.oak.plugins.index.lucene.hybrid.NRTIndexFactory) at org.apache.jackrabbit.oak.plugins.index.lucene.LuceneIndexNodeManager.open(LuceneIndexNodeManager.java:73) at org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker$1.leave(IndexTracker.java:154) at org.apache.jackrabbit.oak.spi.commit.EditorDiff.childNodeChanged(EditorDiff.java:152) at org.apache.jackrabbit.oak.composite.CompositeNodeState$WrappingDiff.childNodeChanged(CompositeNodeState.java:309) at org.apache.jackrabbit.oak.composite.CompositeNodeState$ChildrenDiffFilter.childNodeChanged(CompositeNodeState.java:256) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer.compareExisting(JsopNodeStateDiffer.java:100) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer.access$000(JsopNodeStateDiffer.java:27) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer$1.childNodeChanged(JsopNodeStateDiffer.java:65) at org.apache.jackrabbit.oak.plugins.document.DiffCache.parseJsopDiff(DiffCache.java:118) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer.compare(JsopNodeStateDiffer.java:51) at org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.compare(DocumentNodeStore.java:1766) at org.apache.jackrabbit.oak.plugins.document.AbstractDocumentNodeState.compareAgainstBaseState(AbstractDocumentNodeState.java:113) at org.apache.jackrabbit.oak.composite.CompositeNodeState.compareAgainstBaseState(CompositeNodeState.java:163) at org.apache.jackrabbit.oak.spi.commit.EditorDiff.childNodeChanged(EditorDiff.java:147) at org.apache.jackrabbit.oak.composite.CompositeNodeState$WrappingDiff.childNodeChanged(CompositeNodeState.java:309) at org.apache.jackrabbit.oak.composite.CompositeNodeState$ChildrenDiffFilter.childNodeChanged(CompositeNodeState.java:256) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer.compareExisting(JsopNodeStateDiffer.java:100) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer.access$000(JsopNodeStateDiffer.java:27) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer$1.childNodeChanged(JsopNodeStateDiffer.java:65) at org.apache.jackrabbit.oak.plugins.document.DiffCache.parseJsopDiff(DiffCache.java:118) at org.apache.jackrabbit.oak.plugins.document.JsopNodeStateDiffer.compare(JsopNodeStateDiffer.java:51) at org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.compare(DocumentNodeStore.java:1766) at org.apache.jackrabbit.oak.plugins.document.AbstractDocumentNodeState.compareAgainstBaseState(AbstractDocumentNodeState.java:113) at org.apache.jackrabbit.oak.composite.CompositeNodeState.compareAgainstBaseState(CompositeNodeState.java:163) at org.apache.jackrabbit.oak.spi.commit.EditorDiff.process(EditorDiff.java:51) at org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker.diffAndUpdate(IndexTracker.java:165) - locked <0x67aaaebc> (a org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker) at org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker.update(IndexTracker.java:120) - locked <0x67aaaebc> (a org.apache.jackrabbit.oak.plugins.index.lucene.IndexTracker) at org.apache.jackrabbit.oak.plugins.index.lucene.LuceneIndexProvider.contentChanged(LuceneIndexProvider.java:73) at org.apache.jackrabbit.oak.spi.commit.BackgroundObserver$1$1.call(BackgroundObserver.java:127) at org.apache.jackrabbit.oak.spi.commit.BackgroundObserver$1$1.call(BackgroundObserver.java:121) atjava.util.concurrent.FutureTask.run(FutureTask.java:264) atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) atjava.lang.Thread.run(Thread.java:834)