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From "Tsz Wo (Nicholas), SZE (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1257) Race condition on FSNamesystem#recentInvalidateSets introduced by HADOOP-5124
Date Tue, 08 Nov 2011 23:21:51 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13146645#comment-13146645
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Tsz Wo (Nicholas), SZE commented on HDFS-1257:
----------------------------------------------

The only unsync access to recentInvalidateSets is InvalidateQueueProcessingStats.postCheckIsLastCycle(..).
 It is calling isEmpty() and so it not a problem.

After looking at QueueProcessingStatistics a little bit, I suspect that there is a bug in
counting cycles.  The potential bug is not related the patch.

+1 the 0.20s patch looks good.
                
> Race condition on FSNamesystem#recentInvalidateSets 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
>    Affects Versions: 0.23.0
>            Reporter: Ramkumar Vadali
>            Assignee: Eric Payne
>             Fix For: 0.23.0
>
>         Attachments: HDFS-1257-branch-0.20-security.patch, HDFS-1257.1.20110810.patch,
HDFS-1257.2.20110812.patch, HDFS-1257.3.20110815.patch, HDFS-1257.4.20110816.patch, HDFS-1257.5.20110817.patch,
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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