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https://issues.apache.org/jira/browse/TAJO-704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14074125#comment-14074125
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ASF GitHub Bot commented on TAJO-704:
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Github user jihoonson commented on the pull request:
https://github.com/apache/tajo/pull/77#issuecomment-50111555
@blrunner, thanks for the great contribution!
I tested the latest patch on a real cluster, and it seems that there are a
couple of problems.
Here are descriptions.
* When HA mode is disabled, the web UI doesn't work well.
* There are some problems when derby is used as catalog store.
* I couldn't execute the backup master due to the duplicated pid problem.
* The duplicated catalog uri also incurred a problem.
* When I used a different catalog uri as a workaround for the above
problem, there were differences between the catalog of active master and that
of backup master, obviously.
* I manually added tables to the backup master catalog to test the failover
during the query execution. When the active master is killed, the backup master
becomes to active and every worker is registered to the changed active master
successfully, but the information of executed query is disappeared.
> TajoMaster HA
> -------------
>
> Key: TAJO-704
> URL: https://issues.apache.org/jira/browse/TAJO-704
> Project: Tajo
> Issue Type: New Feature
> Components: tajo master
> Affects Versions: 0.9.0
> Reporter: Jaehwa Jung
> Assignee: Jaehwa Jung
> Fix For: 0.9.0
>
> Attachments: TAJO-704.Henrick.01.patch.txt, TajoMasterHAdraft.pdf
>
>
> TajoMaster is a Single Point of Failure in a Tajo Cluster because TajoMaster
> is the central controlling entity for all components of the Tajo system.
> TajoMaster failure prevents clients from submitting new queries to the
> cluster, and results in the disruption of the ability to run insert overwrite
> queries because the TajoWorker can’t apply its statistical information to
> CatalogStore. Therefore, the high-availability (HA) of TajoMaster is
> essential for the high-availability of Tajo generally.
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