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https://issues.apache.org/jira/browse/HBASE-4899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13160630#comment-13160630
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stack commented on HBASE-4899:
------------------------------
+1 on patch.
Running tests locally before commit. The above failures shouldn't be because
of this patch.
> Region would be assigned twice easily with continually killing server and
> moving region in testing environment
> ---------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-4899
> URL: https://issues.apache.org/jira/browse/HBASE-4899
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.92.1
> Reporter: chunhui shen
> Assignee: chunhui shen
> Priority: Critical
> Attachments: hbase-4899.patch, hbase-4899v2.patch, hbase-4899v3.patch
>
>
> Before assigning region in ServerShutdownHandler#process, it will check
> whether region is in RIT,
> however, this checking doesn't work as the excepted in the following case:
> 1.move region A from server B to server C
> 2.kill server B
> 3.start server B immediately
> Let's see what happen in the code for the above case
> {code}
> for step1:
> 1.1 server B close the region A,
> 1.2 master setOffline for region
> A,(AssignmentManager#setOffline:this.regions.remove(regionInfo))
> 1.3 server C start to open region A.(Not completed)
> for step3:
> master ServerShutdownHandler#process() for server B
> {
> ..
> splitlog()
> ...
> List<RegionState> regionsInTransition =
> this.services.getAssignmentManager()
> .processServerShutdown(this.serverName);
> ...
> Skip regions that were in transition unless CLOSING or PENDING_CLOSE
> ...
> assign region
> }
> {code}
> In fact, when running
> ServerShutdownHandler#process()#this.services.getAssignmentManager().processServerShutdown(this.serverName),
> region A is in RIT (step1.3 not completed), but the return List<RegionState>
> regionsInTransition doesn't contain it, because region A has removed from
> AssignmentManager.regions by AssignmentManager#setOffline in step 1.2
> Therefore, region A will be assigned twice.
> Actually, one server killed and started twice will also easily cause region
> assigned twice.
> Exclude the above reason, another probability :
> when execute ServerShutdownHandler#process()#MetaReader.getServerUserRegions
> ,region is included which is in RIT now.
> But after completing MetaReader.getServerUserRegions, the region has been
> opened in other server and is not in RIT now.
> In our testing environment where balancing,moving and killing are executed
> periodly, assigning region twice often happens, and it is hateful because it
> will affect other test cases.
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