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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16788) Race in compacted file deletion between HStore close() and closeAndArchiveCompactedFiles()
Date Fri, 07 Oct 2016 05:33:20 GMT

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ramkrishna.s.vasudevan commented on HBASE-16788:
------------------------------------------------

bq.Modify HStore.closeAndArchiveCompactedFiles(): use writelock instead of readlock and move
the call to removeCompactedfiles() inside the lock. This means the read operations will be
blocked while the files are being archived, which is bad.
Yes. That is why went ahead with readLock.
bq.Synchronize closeAndArchiveCompactedFiles() and modify close() to call it instead of calling
removeCompactedfiles() directly
If we do this, then the clearCompactedfiles inside removeCompactedfiles should not take the
write lock once again or else it may lead to dead lock. But may be we need to handle it better.Will
see

bq.Add a separate lock for compacted files removal and use in closeAndArchiveCompactedFiles()
and close()
Yes. Seems to be good soln. Let me check if there is some other way out of it. 

> Race in compacted file deletion between HStore close() and closeAndArchiveCompactedFiles()
> ------------------------------------------------------------------------------------------
>
>                 Key: HBASE-16788
>                 URL: https://issues.apache.org/jira/browse/HBASE-16788
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 1.3.0
>            Reporter: Gary Helmling
>            Assignee: Gary Helmling
>            Priority: Blocker
>
> HBASE-13082 changed the way that compacted files are archived from being done inline
on compaction completion to an async cleanup by the CompactedHFilesDischarger chore.  It looks
like the changes to HStore to support this introduced a race condition in the compacted HFile
archiving.
> In the following sequence, we can wind up with two separate threads trying to archive
the same HFiles, causing a regionserver abort:
> # compaction completes normally and the compacted files are added to {{compactedfiles}}
in HStore's DefaultStoreFileManager
> # *threadA*: CompactedHFilesDischargeHandler runs in a RS executor service, calling closeAndArchiveCompactedFiles()
> ## obtains HStore readlock
> ## gets a copy of compactedfiles
> ## releases readlock
> # *threadB*: calls HStore.close() as part of region close
> ## obtains HStore writelock
> ## calls DefaultStoreFileManager.clearCompactedfiles(), getting a copy of same compactedfiles
> # *threadA*: calls HStore.removeCompactedfiles(compactedfiles)
> ## archives files in {compactedfiles} in HRegionFileSystem.removeStoreFiles()
> ## call HStore.clearCompactedFiles()
> ## waits on write lock
> # *threadB*: continues with close()
> ## calls removeCompactedfiles(compactedfiles)
> ## calls HRegionFIleSystem.removeStoreFiles() -> HFileArchiver.archiveStoreFiles()
> ## receives FileNotFoundException because the files have already been archived by threadA
> ## throws IOException
> # RS aborts
> I think the combination of fetching the compactedfiles list and removing the files needs
to be covered by locking.  Options I see are:
> * Modify HStore.closeAndArchiveCompactedFiles(): use writelock instead of readlock and
move the call to removeCompactedfiles() inside the lock.  This means the read operations will
be blocked while the files are being archived, which is bad.
> * Synchronize closeAndArchiveCompactedFiles() and modify close() to call it instead of
calling removeCompactedfiles() directly
> * Add a separate lock for compacted files removal and use in closeAndArchiveCompactedFiles()
and close()



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