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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1908) ROOT not reassigned if only one regionserver left
Date Thu, 15 Oct 2009 19:15:31 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1908?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12766183#action_12766183
] 

Jonathan Gray commented on HBASE-1908:
--------------------------------------

Reproduced on clean branch as described.  If you have two regionservers, one with META and
one with ROOT, if you kill the regionserver hosting ROOT it doesn't ever get reassigned.

Odd behavior though.  The META region gets reassigned to the regionserver tho it was never
unassigned.

Master log:  http://pastebin.com/mb4fed51

RegionServer log: http://pastebin.com/m3e079b36

> ROOT not reassigned if only one regionserver left
> -------------------------------------------------
>
>                 Key: HBASE-1908
>                 URL: https://issues.apache.org/jira/browse/HBASE-1908
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.20.1
>            Reporter: Jonathan Gray
>            Priority: Blocker
>             Fix For: 0.20.2, 0.21.0
>
>         Attachments: HBASE-1908-v1.patch
>
>
> Yannis on the list uncovered an assignment bug:
> {quote}
> I performed additional testing with some alternate configurations and the problem arises
(ONLY) when there is only one regionserver left which has the META table already assigned
to it. 
> In this case the ROOT table does not get assigned to the last regionserver (which holds
the META table).
> Interestingly enough though when there is only one regionserver left that has the ROOT
table already assign to it then it can also have the META table re-assigned to it (if again
is the only server - i.e. in this scenario you can have one regionserver holding both the
META and ROOT tables).
> Unless I am missing something I cannot find any reason why we cannot assign the ROOT
table to the regionserver that manages the META table if it is the only one remaining (again
it is an extreme case I agree that this can happen).
> I applied and tested a fix (at the hbase-0.20.0 codebase) in the RegionManager::regionsAwaitingAssignment
where I add the root table in the regionstoAssign set if the it is the metaServer and also
the only server.
> {quote}

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