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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1257) Race condition introduced by HADOOP-5124
Date Tue, 28 Jun 2011 16:40:17 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13056618#comment-13056618
] 

Eric Payne commented on HDFS-1257:
----------------------------------

Hi Konstantin and Ramkumar,

I am running into this problem under stress conditions. In my case, it is a case of iteration
and modification of recentInvalidateSets happening at the same time (reference the stack traceback).
I can reproduce this fairly often using an environment that stresses the namenode.

Was there a resolution to this issue? I agree that there needs to be a general solution to
protect recentInvalidateSets.

If you don't have any objections, I will go ahead and post a patch that is (possibly) more
of a general solution.

Thanks,
-Eric

> Race condition introduced by HADOOP-5124
> ----------------------------------------
>
>                 Key: HDFS-1257
>                 URL: https://issues.apache.org/jira/browse/HDFS-1257
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>            Reporter: Ramkumar Vadali
>         Attachments: HDFS-1257.patch
>
>
> HADOOP-5124 provided some improvements to FSNamesystem#recentInvalidateSets. But it introduced
unprotected access to the data structure recentInvalidateSets. Specifically, FSNamesystem.computeInvalidateWork
accesses recentInvalidateSets without read-lock protection. If there is concurrent activity
(like reducing replication on a file) that adds to recentInvalidateSets, the name-node crashes
with a ConcurrentModificationException.

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