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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6089) SSH and AM.joinCluster causes Concurrent Modification exception.
Date Wed, 30 May 2012 06:35:23 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13285425#comment-13285425
] 

ramkrishna.s.vasudevan commented on HBASE-6089:
-----------------------------------------------

Yes.  As per the javadoc for entrySet in ConcurrentSkipListMap
{code}
     * <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
     * that will never throw {@link ConcurrentModificationException},
     * and guarantees to traverse elements as they existed upon
     * construction of the iterator, and may (but is not guaranteed to)
     * reflect any modifications subsequent to construction.
{code}

So as per the current JIRA when we iterate the this.region in joincluster we need to get the
actual regions there.  If SSH tries to modify we may even try to iterate those regions.
So making it to ConcurrentSkipListMap will not help us here and still we need to go with the
sync block.
So i think the current patch should be fine.
@Stack
What you feel? If it is ok for you , i can commit this?
                
> SSH and AM.joinCluster causes Concurrent Modification exception.
> ----------------------------------------------------------------
>
>                 Key: HBASE-6089
>                 URL: https://issues.apache.org/jira/browse/HBASE-6089
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.92.1, 0.94.0
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: rajeshbabu
>             Fix For: 0.90.7, 0.92.2, 0.96.0, 0.94.1
>
>         Attachments: HBASE-6089_92.patch, HBASE-6089_94.patch, HBASE-6089_trunk.patch
>
>
> AM.regions map is parallely accessed in SSH and Master initialization leading to ConcurrentModificationException.

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