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From "rajeshbabu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8353) -ROOT-/.META. regions are hanging if master restarted while closing -ROOT-/.META. regions on dead RS
Date Wed, 17 Apr 2013 03:27:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13633716#comment-13633716
] 

rajeshbabu commented on HBASE-8353:
-----------------------------------

[~jeffreyz]
bq. Could you please clarify a detailed scenario where catalog table regions are in M_ZK_REGION_CLOSING
state while the hosting RS isn't in deadServers? 
There can be multiple cases but these are rare.
1) CloseRegionHandler thread on live server may not be scheduled on slower machines(by the
time backup master become active and it sees M_ZK_REGION_CLOSING rit on online server).
2) for .META. flushes/compaction may be in progress which blocks closing.

Actual problem here comes if the RS closing catalog regions and master are dead at a time(zk
is stopped/killed).
                
> -ROOT-/.META. regions are hanging if master restarted while closing -ROOT-/.META. regions
on dead RS
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-8353
>                 URL: https://issues.apache.org/jira/browse/HBASE-8353
>             Project: HBase
>          Issue Type: Bug
>          Components: Region Assignment
>    Affects Versions: 0.94.6
>            Reporter: rajeshbabu
>            Assignee: rajeshbabu
>             Fix For: 0.94.8
>
>
> ROOT/META are not getting assigned if master restarted while closing ROOT/META.
> Lets suppose catalog table regions in M_ZK_REGION_CLOSING state during master initialization
and then just we are adding the them to RIT and waiting for TM. {code}
>         if (isOnDeadServer(regionInfo, deadServers) &&
>             (data.getOrigin() == null || !serverManager.isServerOnline(data.getOrigin())))
{
>           // If was on dead server, its closed now. Force to OFFLINE and this
>           // will get it reassigned if appropriate
>           forceOffline(regionInfo, data);
>         } else {
>           // Just insert region into RIT.
>           // If this never updates the timeout will trigger new assignment
>           regionsInTransition.put(encodedRegionName, new RegionState(
>             regionInfo, RegionState.State.CLOSING,
>             data.getStamp(), data.getOrigin()));
>         }
> {code}
> isOnDeadServer always return false to ROOT/META because deadServers is null.
> Even TM cannot close them properly because its not available in online regions since
its not yet assigned.
> {code}
>     synchronized (this.regions) {
>       // Check if this region is currently assigned
>       if (!regions.containsKey(region)) {
>         LOG.debug("Attempted to unassign region " +
>           region.getRegionNameAsString() + " but it is not " +
>           "currently assigned anywhere");
>         return;
>       }
>     }
> {code}

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