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https://issues.apache.org/jira/browse/HBASE-17682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15880874#comment-15880874
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Ted Yu commented on HBASE-17682:
--------------------------------
Patch looks good.
I guess it would be difficult to write unit test for this corner case.
> Region stuck in merging_new state indefinitely
> ----------------------------------------------
>
> Key: HBASE-17682
> URL: https://issues.apache.org/jira/browse/HBASE-17682
> Project: HBase
> Issue Type: Bug
> Affects Versions: 1.3.0
> Reporter: Abhishek Singh Chouhan
> Assignee: Abhishek Singh Chouhan
> Attachments: HBASE-17682.branch-1.3.001.patch,
> HBASE-17682.master.001.patch
>
>
> Ran into issue while tinkering around with a chaos monkey that did splits,
> merges and kills exclusively, which resulted in regions getting stuck in
> transition in merging new state indefinitely which i think happens when the
> rs is killed during the merge but before the ponr, in which case the new
> regions state in master is merging new. When the rs dies at this point the
> master executes RegionStates.serverOffline() for the rs which does
> {code}
> for (RegionState state : regionsInTransition.values()) {
> HRegionInfo hri = state.getRegion();
> if (assignedRegions.contains(hri)) {
> // Region is open on this region server, but in transition.
> // This region must be moving away from this server, or
> splitting/merging.
> // SSH will handle it, either skip assigning, or re-assign.
> LOG.info("Transitioning " + state + " will be handled by
> ServerCrashProcedure for " + sn);
> } else if (sn.equals(state.getServerName())) {
> // Region is in transition on this region server, and this
> // region is not open on this server. So the region must be
> // moving to this server from another one (i.e. opening or
> // pending open on this server, was open on another one.
> // Offline state is also kind of pending open if the region is in
> // transition. The region could be in failed_close state too if we
> have
> // tried several times to open it while this region server is not
> reachable)
> if (state.isPendingOpenOrOpening() || state.isFailedClose() ||
> state.isOffline()) {
> LOG.info("Found region in " + state +
> " to be reassigned by ServerCrashProcedure for " + sn);
> rits.add(hri);
> } else if(state.isSplittingNew()) {
> regionsToCleanIfNoMetaEntry.add(state.getRegion());
> } else {
> LOG.warn("THIS SHOULD NOT HAPPEN: unexpected " + state);
> }
> }
> }
> {code}
> We donot handle merging new here and end up with "THIS SHOULD NOT HAPPEN:
> unexpected ...". Post this we have the new region which does not have any
> data stuck which leads to the balancer not running.
> I think we should handle mergingnew the same way as splittingnew.
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