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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-543) A region's state is kept in several places in the master opening the possibility for race conditions
Date Mon, 22 Dec 2008 22:27:44 GMT

    [ https://issues.apache.org/jira/browse/HBASE-543?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12658698#action_12658698

stack commented on HBASE-543:

Patch passed with loading and start/stops of hbase.  Also passed unit tests.

Is this safe?
+        if (!master.regionManager.isUnassigned(i) &&
+            !master.regionManager.isAssigned(i.getRegionName()) &&
+            !master.regionManager.isPending(i.getRegionName())) {
+          master.regionManager.setUnassigned(i, false);
Should this all be done in a sync block inside in regionManager?  Or is it 'safe' because
we process one message at a time?  There are a few of these multiple tests.  This glob of
checks is done in a few places.  Put them together in a single method?  Would be easier to
read (Latter point is not important for now).

If above is safe, then I'm +1 on committing last version of this patch.   Can address other
minor stuff later.

> A region's state is kept in several places in the master opening the possibility for
race conditions
> ----------------------------------------------------------------------------------------------------
>                 Key: HBASE-543
>                 URL: https://issues.apache.org/jira/browse/HBASE-543
>             Project: Hadoop HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.1.0, 0.1.1, 0.2.0
>            Reporter: Jim Kellerman
>            Assignee: Jim Kellerman
>             Fix For: 0.19.0
>         Attachments: 543.patch, 543.patch, 543.patch, recent-changes.patch, regionstate.txt
> A region's state exists in multiple maps in the RegionManager: unassignedRegions, pendingRegions,
regionsToClose, closingRegions, regionsToDelete, etc.
> One of these race conditions was found in HBASE-534.
> For HBase-0.1.x, we should just patch the holes we find.
> The ultimate solution (which requires a lot of changes in HMaster) should be applied
to HBase trunk.
> Proposed solution:
> Create a class that encapsulates a region's state and provide synchronized access to
the class that validates state changes.
> There should be a single structure that holds regions in these transitional states and
it should be a synchronized collection of some kind.

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