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From "Jimmy Xiang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9514) Prevent region from assigning before log splitting is done
Date Tue, 17 Sep 2013 16:31:55 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13769660#comment-13769660

Jimmy Xiang commented on HBASE-9514:

bq. should we rename AM.acquireLock -> AM.acquireRegionLock()
Sure, will do.
bq. Why not do this for meta?
Let me think how to cover meta as well.
bq. Is it safe to expire a server like this. It means the master cannot connect to it, but
it may still have the zk lease. 
We have waited for longer than the ZK session timeout. It should be expired.  It is ok to
expire twice.

The timeout should be active. I will fix it.

The idea of the patch is to remember the last known region server a region is assigned to.
Whenever we try to assign a region, we check if the last known region server of the region
is done with log splitting. If not, we don't assign it, and let SSH to complete log splitting
and re-assign. We clear the last known region server info when SSH finishes log splitting,
or the region is properly closed. The idea is simple but there are several racing points to
take care.
> Prevent region from assigning before log splitting is done
> ----------------------------------------------------------
>                 Key: HBASE-9514
>                 URL: https://issues.apache.org/jira/browse/HBASE-9514
>             Project: HBase
>          Issue Type: Bug
>          Components: Region Assignment
>            Reporter: Jimmy Xiang
>            Assignee: Jimmy Xiang
>            Priority: Blocker
>         Attachments: trunk-9514_v1.patch
> If a region is assigned before log splitting is done by the server shutdown handler,
the edits belonging to this region in the hlogs of the dead server will be lost.
> Generally this is not an issue if users don't assign/unassign a region from hbase shell
or via hbase admin. These commands are marked for experts only in the hbase shell help too.
 However, chaos monkey doesn't care.
> If we can prevent from assigning such regions in a bad time, it would make things a little

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