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From "Jieshan Bean (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5875) Process RIT and Master restart may remove an online server considering it as a dead server
Date Mon, 30 Apr 2012 11:12:48 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13264874#comment-13264874
] 

Jieshan Bean commented on HBASE-5875:
-------------------------------------

Look into the method of CatalogTracker#verifyRootRegionLocation:
{noformat}
public boolean verifyRootRegionLocation(final long timeout)
  throws InterruptedException, IOException {
    AdminProtocol connection = null;
    try {
      connection = waitForRootServerConnection(timeout);
    } catch (NotAllMetaRegionsOnlineException e) {
      // Pass
    } catch (ServerNotRunningYetException e) {
      // Pass -- remote server is not up so can't be carrying root
    } catch (UnknownHostException e) {
      // Pass -- server name doesn't resolve so it can't be assigned anything.
    }
    return (connection == null)? false:
      verifyRegionLocation(connection,
        this.rootRegionTracker.getRootRegionLocation(), ROOT_REGION_NAME);
  }
{noformat}
I'm thinking about an approach which can handle this issue according to different exception.

e.g. if we got an ServerNotRunningYetException, we can process splitLogAndExpireIfOnline.
But if we got an NotServingRegionException, we should not do that.


                
> Process RIT and Master restart may remove an online server considering it as a dead server
> ------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5875
>                 URL: https://issues.apache.org/jira/browse/HBASE-5875
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.92.1
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 0.94.1
>
>
> If on master restart it finds the ROOT/META to be in RIT state, master tries to assign
the ROOT region through ProcessRIT.
> Master will trigger the assignment and next will try to verify the Root Region Location.
> Root region location verification is done seeing if the RS has the region in its online
list.
> If the master triggered assignment has not yet been completed in RS then the verify root
region location will fail.
> Because it failed 
> {code}
> splitLogAndExpireIfOnline(currentRootServer);
> {code}
> we do split log and also remove the server from online server list. Ideally here there
is nothing to do in splitlog as no region server was restarted.
> So master, though the server is online, master just invalidates the region server.
> In a special case, if i have only one RS then my cluster will become non operative.

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