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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-1908) ROOT not reassigned if only one regionserver left
Date Thu, 15 Oct 2009 18:24:31 GMT
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

Yannis on the list uncovered an assignment bug:

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.

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