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From "chunhui shen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8251) enable SSH before assign META on Master startup
Date Thu, 04 Apr 2013 02:57:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13621689#comment-13621689

chunhui shen commented on HBASE-8251:

Good catch, but move enabling SSH before assign META would cause another META data loss case:
1. Assign ROOT.
2. Block until ROOT be opened.
3. Enable SSH
4. Assign META.
5. Block until META be opened.

if META RS is killed between step 3 and step 4, SSH will start handling it (including split
step 4 will assign the META, it means META region would loss the data from the hlog.

In order to fix related cases, two other things should also be noticed:
1.The concurrency of SSH#process and HMaster#splitLogAndExpireIfOnline
2.Before completing assignRootAndMeta, A dead META RS will be handled by ServerShutdownHandler,
not MetaServerShutdownHandler, see AssignmentManager#isCarryingMeta

Since we have dropped ROOT in trunk, I think there is no related trouble in trunk.

IMHO, aborting master may be a compromise choice if encounter this case.

> enable SSH before assign META on Master startup
> -----------------------------------------------
>                 Key: HBASE-8251
>                 URL: https://issues.apache.org/jira/browse/HBASE-8251
>             Project: HBase
>          Issue Type: Bug
>          Components: master, Region Assignment
>    Affects Versions: 0.94.6
>            Reporter: Jieshan Bean
>            Assignee: Jieshan Bean
>         Attachments: HBASE-8251-94.patch
> I think HBASE-5918 could not fix this issue. In HMaster#assignRootAndMeta:
> 1. Assign ROOT.
> 2. Block until ROOT be opened.
> 3. Assign META.
> 4. Block until META be opened.
> SSH is enabled after step 4. So if the RS who host ROOT dies before step 4, master will
be blocked.

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