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https://issues.apache.org/jira/browse/HBASE-8353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13634850#comment-13634850
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rajeshbabu commented on HBASE-8353:
-----------------------------------
in unassign of a region
1) create closing node
2) send close request to the server holding the region.
one more problem here is if master restarted before 2nd step there is a
possible double assignment if the RS holding the region is online.
in processRegionInTransition we need to make a decision whether to call
unassign or just to add to rit. In case of catalog regions unassign itself
fails because online regions map dont have it.
> -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
>
> Attachments: HBASE-8353_94.patch
>
>
> 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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