Marcel Reutegger created OAK-2815:
-------------------------------------
Summary: Persistent cache may block commit
Key: OAK-2815
URL: https://issues.apache.org/jira/browse/OAK-2815
Project: Jackrabbit Oak
Issue Type: Bug
Affects Versions: 1.2
Reporter: Marcel Reutegger
Assignee: Marcel Reutegger
Fix For: 1.3.0
The persistent cache may block a commit for a rather long time if the
generation is switched during the commit. The default configuration tells the
persistent cache to compact the store when it is closed. This is exactly what
happens when a generation is switched.
I think it would be best to disable compaction.
I was able to reproduce it with the {{ContinuousRevisionGCTest}} in oak-run
with {{-DgarbageRatio=0.9}}, but it probably also happens with the default
garbage ratio of 0.5.
Once the MVStore reaches 1GB, the console will show something like this:
{noformat}
Performed RevisionGC in 6.331 s (VersionGCStats{ignoredGCDueToCheckPoint=false,
deletedDocGCCount=54054, splitDocGCCount=0, intermediateSplitDocGCCount=0,
timeToCollectDeletedDocs=622.8 ms, timeTakenToDeleteDocs=5.708 s})
.................
Performed RevisionGC in 9.232 s (VersionGCStats{ignoredGCDueToCheckPoint=false,
deletedDocGCCount=26026, splitDocGCCount=0, intermediateSplitDocGCCount=0,
timeToCollectDeletedDocs=6.549 s, timeTakenToDeleteDocs=2.682 s})
Performed RevisionGC in 1.269 s (VersionGCStats{ignoredGCDueToCheckPoint=false,
deletedDocGCCount=12012, splitDocGCCount=0, intermediateSplitDocGCCount=0,
timeToCollectDeletedDocs=133.5 ms, timeTakenToDeleteDocs=1.134 s})
Performed RevisionGC in 20.49 ms
(VersionGCStats{ignoredGCDueToCheckPoint=false, deletedDocGCCount=0,
splitDocGCCount=0, intermediateSplitDocGCCount=0,
timeToCollectDeletedDocs=19.50 ms, timeTakenToDeleteDocs=0.000 ns})
.15:19:16.682 [DocumentNodeStore background update thread] INFO
o.a.j.o.p.document.DocumentNodeStore - Background operations stats (clean:0,
split:0, lock:35581, write:1, num:5)
............
Performed RevisionGC in 8.449 s (VersionGCStats{ignoredGCDueToCheckPoint=false,
deletedDocGCCount=2002, splitDocGCCount=0, intermediateSplitDocGCCount=0,
timeToCollectDeletedDocs=8.276 s, timeTakenToDeleteDocs=171.7 ms})
{noformat}
The background update thread had to wait 35 seconds for the
backgroundOperations lock, which was held by the committing thread:
{noformat}
"Thread-2" prio=5 tid=0x00007f986b9a7800 nid=0x6803 runnable
[0x0000000112780000]
java.lang.Thread.State: RUNNABLE
at org.h2.compress.CompressLZF.compress(CompressLZF.java:239)
at org.h2.mvstore.Page.write(Page.java:754)
at org.h2.mvstore.Page.writeUnsavedRecursive(Page.java:816)
at org.h2.mvstore.Page.writeUnsavedRecursive(Page.java:822)
at org.h2.mvstore.Page.writeUnsavedRecursive(Page.java:822)
at org.h2.mvstore.MVStore.storeNowTry(MVStore.java:1065)
at org.h2.mvstore.MVStore.storeNow(MVStore.java:981)
at org.h2.mvstore.MVStore.commitAndSave(MVStore.java:970)
- locked <0x00000007e15cccf0> (a org.h2.mvstore.MVStore)
at org.h2.mvstore.MVStore.beforeWrite(MVStore.java:2084)
at org.h2.mvstore.MVMap.beforeWrite(MVMap.java:1046)
at org.h2.mvstore.MVMap.copy(MVMap.java:1231)
at org.h2.mvstore.MVMap.copy(MVMap.java:1248)
at org.h2.mvstore.MVMap.copy(MVMap.java:1248)
at org.h2.mvstore.MVMap.copyFrom(MVMap.java:1218)
at org.h2.mvstore.MVStoreTool.compact(MVStoreTool.java:493)
at org.h2.mvstore.MVStoreTool.compact(MVStoreTool.java:458)
at org.h2.mvstore.MVStoreTool.compact(MVStoreTool.java:404)
at
org.apache.jackrabbit.oak.plugins.document.persistentCache.PersistentCache$1.closeStore(PersistentCache.java:235)
- locked <0x00000007c0c82760> (a
org.apache.jackrabbit.oak.plugins.document.persistentCache.PersistentCache$1)
at
org.apache.jackrabbit.oak.plugins.document.persistentCache.PersistentCache.switchGenerationIfNeeded(PersistentCache.java:372)
- locked <0x00000007c03a6c00> (a
org.apache.jackrabbit.oak.plugins.document.persistentCache.PersistentCache)
at
org.apache.jackrabbit.oak.plugins.document.persistentCache.NodeCache.write(NodeCache.java:85)
at
org.apache.jackrabbit.oak.plugins.document.persistentCache.NodeCache.put(NodeCache.java:130)
at
org.apache.jackrabbit.oak.plugins.document.LocalDiffCache$1.done(LocalDiffCache.java:98)
at
org.apache.jackrabbit.oak.plugins.document.Commit.applyToCache(Commit.java:602)
at
org.apache.jackrabbit.oak.plugins.document.CommitQueue.afterTrunkCommit(CommitQueue.java:127)
- locked <0x00000007c03a46f0> (a
org.apache.jackrabbit.oak.plugins.document.CommitQueue)
at
org.apache.jackrabbit.oak.plugins.document.CommitQueue.done(CommitQueue.java:83)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.done(DocumentNodeStore.java:644)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.persist(DocumentNodeStoreBranch.java:338)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.persist(DocumentNodeStoreBranch.java:304)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.access$200(DocumentNodeStoreBranch.java:52)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch$InMemory.merge(DocumentNodeStoreBranch.java:541)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.merge0(DocumentNodeStoreBranch.java:230)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStoreBranch.merge(DocumentNodeStoreBranch.java:171)
at
org.apache.jackrabbit.oak.plugins.document.DocumentRootBuilder.merge(DocumentRootBuilder.java:158)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.merge(DocumentNodeStore.java:1490)
at
org.apache.jackrabbit.oak.core.MutableRoot.commit(MutableRoot.java:247)
at
org.apache.jackrabbit.oak.jcr.delegate.SessionDelegate.commit(SessionDelegate.java:341)
at
org.apache.jackrabbit.oak.jcr.delegate.SessionDelegate.save(SessionDelegate.java:487)
at
org.apache.jackrabbit.oak.jcr.session.SessionImpl$8.performVoid(SessionImpl.java:424)
at
org.apache.jackrabbit.oak.jcr.delegate.SessionDelegate.performVoid(SessionDelegate.java:268)
at
org.apache.jackrabbit.oak.jcr.session.SessionImpl.save(SessionImpl.java:421)
at
org.apache.jackrabbit.oak.ContinuousRevisionGCTest$Writer.run(ContinuousRevisionGCTest.java:72)
at java.lang.Thread.run(Thread.java:745)
{noformat}
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