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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6289) ROOT region doesn't get re-assigned in ServerShutdownHandler if the RS is still working but only the RS's ZK node expires.
Date Thu, 28 Jun 2012 13:22:44 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13403085#comment-13403085
] 

ramkrishna.s.vasudevan commented on HBASE-6289:
-----------------------------------------------

@Maryann
Good one Maraynn. Nice catch.
I have one suggestion.  Can we just say assignRoot instead of verifying the root location
like how we do assignMeta.

{code}
this.services.getAssignmentManager().assignMeta();
{code}
similarly can we say
{code}
if (isCarryingRoot()) { // -ROOT-
        LOG.info("Server " + serverName +
            " was carrying ROOT. Trying to assign.");
        this.services.getAssignmentManager().
          regionOffline(HRegionInfo.ROOT_REGIONINFO);
        this.services.getAssignmentManager().assignRoot();
      }
{code}
Because we are sure that the root is down here.  What do you feel?
                
> ROOT region doesn't get re-assigned in ServerShutdownHandler if the RS is still working
but only the RS's ZK node expires.
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-6289
>                 URL: https://issues.apache.org/jira/browse/HBASE-6289
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.90.6, 0.94.0
>            Reporter: Maryann Xue
>            Assignee: Maryann Xue
>            Priority: Critical
>         Attachments: HBASE-6289.patch
>
>
> The ROOT RS has some network problem and its ZK node expires first, which kicks off the
ServerShutdownHandler. it calls verifyAndAssignRoot() to try to re-assign ROOT. At that time,
the RS is actually still working and passes the verifyRootRegionLocation() check, so the ROOT
region is skipped from re-assignment.
>   private void verifyAndAssignRoot()
>   throws InterruptedException, IOException, KeeperException {
>     long timeout = this.server.getConfiguration().
>       getLong("hbase.catalog.verification.timeout", 1000);
>     if (!this.server.getCatalogTracker().verifyRootRegionLocation(timeout)) {
>       this.services.getAssignmentManager().assignRoot();
>     }
>   }
> After a few moments, this RS encounters DFS write problem and decides to abort. The RS
then soon gets restarted from commandline, and constantly report:
> 2012-06-27 23:13:08,627 DEBUG org.apache.hadoop.hbase.regionserver.HRegionServer: NotServingRegionException;
Region is not online: -ROOT-,,0
> 2012-06-27 23:13:08,627 DEBUG org.apache.hadoop.hbase.regionserver.HRegionServer: NotServingRegionException;
Region is not online: -ROOT-,,0
> 2012-06-27 23:13:08,628 DEBUG org.apache.hadoop.hbase.regionserver.HRegionServer: NotServingRegionException;
Region is not online: -ROOT-,,0
> 2012-06-27 23:13:08,628 DEBUG org.apache.hadoop.hbase.regionserver.HRegionServer: NotServingRegionException;
Region is not online: -ROOT-,,0
> 2012-06-27 23:13:08,630 DEBUG org.apache.hadoop.hbase.regionserver.HRegionServer: NotServingRegionException;
Region is not online: -ROOT-,,0

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