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https://issues.apache.org/jira/browse/ZOOKEEPER-1936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15123906#comment-15123906
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Chris Nauroth commented on ZOOKEEPER-1936:
------------------------------------------

[~yuzhih...@gmail.com], my understanding is that you only can repro this in 
standalone mode, not when deploying a full ensemble.  Is that correct?  Did you 
get to a point where you had a consistent repro and were able to verify that 
this patch helped fix it?

The logic change looks correct to me, but I'm trying to figure out if there is 
really something more going on, as suggested in earlier comments.  Thanks!

> Server exits when unable to create data directory due to race 
> --------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1936
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1936
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.4.6, 3.5.0
>            Reporter: Harald Musum
>            Assignee: Andrew Purtell
>            Priority: Minor
>         Attachments: ZOOKEEPER-1936.patch, ZOOKEEPER-1936.v2.patch, 
> ZOOKEEPER-1936.v3.patch, ZOOKEEPER-1936.v3.patch
>
>
> We sometime see issues with ZooKeeper server not starting and seeing this 
> error in the log:
> [2014-05-27 09:29:48.248] ERROR   : -               
> .org.apache.zookeeper.server.ZooKeeperServerMain    Unexpected exception,
> exiting abnormally\nexception=\njava.io.IOException: Unable to create data
> directory /home/y/var/zookeeper/version-2\n\tat
> org.apache.zookeeper.server.persistence.FileTxnSnapLog.<init>(FileTxnSnapLog.java:85)\n\tat
> org.apache.zookeeper.server.ZooKeeperServerMain.runFromConfig(ZooKeeperServerMain.java:103)\n\tat
> org.apache.zookeeper.server.ZooKeeperServerMain.initializeAndRun(ZooKeeperServerMain.java:86)\n\tat
> org.apache.zookeeper.server.ZooKeeperServerMain.main(ZooKeeperServerMain.java:52)\n\tat
> org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:116)\n\tat
> org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)\n\t
> [...]
> Stack trace from JVM gives this:
> "PurgeTask" daemon prio=10 tid=0x000000000201d000 nid=0x1727 runnable
> [0x00007f55d7dc7000]
>    java.lang.Thread.State: RUNNABLE
>     at java.io.UnixFileSystem.createDirectory(Native Method)
>     at java.io.File.mkdir(File.java:1310)
>     at java.io.File.mkdirs(File.java:1337)
>     at
> org.apache.zookeeper.server.persistence.FileTxnSnapLog.<init>(FileTxnSnapLog.java:84)
>     at org.apache.zookeeper.server.PurgeTxnLog.purge(PurgeTxnLog.java:68)
>     at
> org.apache.zookeeper.server.DatadirCleanupManager$PurgeTask.run(DatadirCleanupManager.java:140)
>     at java.util.TimerThread.mainLoop(Timer.java:555)
>     at java.util.TimerThread.run(Timer.java:505)
> "zookeeper server" prio=10 tid=0x00000000027df800 nid=0x1715 runnable
> [0x00007f55d7ed8000]
>    java.lang.Thread.State: RUNNABLE
>     at java.io.UnixFileSystem.createDirectory(Native Method)
>     at java.io.File.mkdir(File.java:1310)
>     at java.io.File.mkdirs(File.java:1337)
>     at
> org.apache.zookeeper.server.persistence.FileTxnSnapLog.<init>(FileTxnSnapLog.java:84)
>     at
> org.apache.zookeeper.server.ZooKeeperServerMain.runFromConfig(ZooKeeperServerMain.java:103)
>     at
> org.apache.zookeeper.server.ZooKeeperServerMain.initializeAndRun(ZooKeeperServerMain.java:86)
>     at
> org.apache.zookeeper.server.ZooKeeperServerMain.main(ZooKeeperServerMain.java:52)
>     at
> org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:116)
>     at
> org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)
> [...]
> So it seems that when autopurge is used (as it is in our case), it might 
> happen at the same time as starting the server itself. In FileTxnSnapLog() it 
> will check if the directory exists and create it if not. These two tasks do 
> this at the same time, and mkdir fails and server exits the JVM.



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