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https://issues.apache.org/jira/browse/HBASE-3872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13031028#comment-13031028
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stack commented on HBASE-3872:
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This bug caused hbase to delete a whole region. Critical.
> Hole in split transaction rollback; edits to .META. need to be rolled back
> even if it seems like they didn't make it
> --------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-3872
> URL: https://issues.apache.org/jira/browse/HBASE-3872
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.90.3
> Reporter: stack
> Assignee: stack
> Priority: Critical
> Fix For: 0.90.4
>
>
> Saw this interesting one on a cluster of ours. The cluster was configured
> with too few handlers so lots of the phenomeneon where actions were queued
> but then by the time they got into the server and tried respond to the
> client, the client had disconnected because of the timeout of 60 seconds.
> Well, the meta edits for a split were queued at the regionserver carrying
> .META. and by the time it went to write back, the client had gone (the first
> insert of parent offline with daughter regions added as info:splitA and
> info:splitB). The client presumed the edits failed and 'successfully' rolled
> back the transaction (failing to undo .META. edits thinking they didn't go
> through).
> A few minutes later the .META. scanner on master runs. It sees 'no
> references' in daughters -- the daughters had been cleaned up as part of the
> split transaction rollback -- so it thinks its safe to delete the parent.
> Two things:
> + Tighten up check in master... need to check daughter region at least exists
> and possibly the daughter region has an entry in .META.
> + Dependent on the edit that fails, schedule rollback edits though it will
> seem like they didn't go through.
> This is pretty critical one.
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