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From "Jonathan Gray (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4497) If region opening fails after updating META HBCK reports it as inconsistent and scanning the region throws NSRE
Date Wed, 28 Sep 2011 18:58:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13116695#comment-13116695
] 

Jonathan Gray commented on HBASE-4497:
--------------------------------------

startcode and timestamp is what i initially thought of.  seems like there could be some weird
situations.  for example, what is to say that the server already in META didn't somehow become
the new assignment destination?

or what if... M tells RS1 to OPEN R1 and to expect RS3:StartCode3 in META.  RS1 locks up right
before doing the META edit, M tells RS2 to OPEN R1 and to also expect RS3:StartCode3 in META.
 I guess this is the atomicity we need, so that should be okay.

one neat idea would be to introduce this region assignment incrementing ID into META.  it
would provide a nice way to debug the movement of a region across the cluster over time and
could also provide the necessary info to use CheckAndPut.
                
> If region opening fails after updating META HBCK reports it as inconsistent and scanning
the region throws NSRE
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-4497
>                 URL: https://issues.apache.org/jira/browse/HBASE-4497
>             Project: HBase
>          Issue Type: Bug
>            Reporter: ramkrishna.s.vasudevan
>            Priority: Critical
>
> As per the discussion in the mail chain "HBCK reporting of possible mismatch in RS assignment"
this JIRA is created.
> Consider two RS-> RS1 and RS2.
> A region tries to open in RS1. But it takes a while.  The RS1 has still not updated meta
and transitioned the node from OPENING to OPENED
> So timeout assigns the region to RS2.  RS2 successfully updates the META and opens the
region.
> Now RS1 tries to act on the region by first updating the META and then transiting the
node to OPENING to OPENED.
> RS1 transiting the node to OPENING to OPENED will fail.  But the META entry will have
RS1 as the latest.
> Now HBCK reports this as an inconsistency and if we try to scan the Region we get NotServingRegionException.

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