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From "Jimmy Xiang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6317) Master clean start up and Partially enabled tables make region assignment inconsistent.
Date Fri, 27 Jul 2012 17:41:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424000#comment-13424000
] 

Jimmy Xiang commented on HBASE-6317:
------------------------------------

HBASE-6272 went in trunk, :)

The inconsistent we are trying to fix here is about the possible double-assignment, right?
 Any other inconsistency?

If it is just for double-assignment, I think it is better to prevent it from AssignmentManager
(or the new RegionStates introduced in HBASE-6272).
Whenever a new region is online, if it is assigned to a server different from that in RegionStates,
we can put the corresponding info to a queue
and make sure it is not still assigned there, without going through zookeeper.

The point is that it's hard to prevent the double-asignment from the source, like this issue.
The reason is racing and distributed issues.
Of course, it is great if we can prevent it from the source.

Based on a consistent, central place, for example, RegionStates, I think it is easier to prevent
from some bad things.


                
> Master clean start up and Partially enabled tables make region assignment inconsistent.
> ---------------------------------------------------------------------------------------
>
>                 Key: HBASE-6317
>                 URL: https://issues.apache.org/jira/browse/HBASE-6317
>             Project: HBase
>          Issue Type: Bug
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: rajeshbabu
>             Fix For: 0.92.2, 0.96.0, 0.94.2
>
>         Attachments: HBASE-6317_94.patch, HBASE-6317_94_3.patch
>
>
> If we have a  table in partially enabled state (ENABLING) then on HMaster restart we
treat it as a clean cluster start up and do a bulk assign.  Currently in 0.94 bulk assign
will not handle ALREADY_OPENED scenarios and it leads to region assignment problems.  Analysing
more on this we found that we have better way to handle these scenarios.
> {code}
> if (false == checkIfRegionBelongsToDisabled(regionInfo)
>             && false == checkIfRegionsBelongsToEnabling(regionInfo)) {
>           synchronized (this.regions) {
>             regions.put(regionInfo, regionLocation);
>             addToServers(regionLocation, regionInfo);
>           }
> {code}
> We dont add to regions map so that enable table handler can handle it.  But as nothing
is added to regions map we think it as a clean cluster start up.
> Will come up with a patch tomorrow.

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