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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12070) Add an option to hbck to fix ZK inconsistencies
Date Thu, 29 Jan 2015 19:22:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14297396#comment-14297396

Ted Yu commented on HBASE-12070:

TestHBaseFsck passes with patch.

Planning to integrate later today.

> Add an option to hbck to fix ZK inconsistencies
> -----------------------------------------------
>                 Key: HBASE-12070
>                 URL: https://issues.apache.org/jira/browse/HBASE-12070
>             Project: HBase
>          Issue Type: Bug
>          Components: hbck
>    Affects Versions: 1.1.0
>            Reporter: Sudarshan Kadambi
>            Assignee: Stephen Yuan Jiang
>             Fix For: 1.1.0
>         Attachments: HBASE-12070.v1-branch-1.patch
> If the HMaster bounces in the middle of table creation, we could be left in a state where
a znode exists for the table, but that hasn't percolated into META or to HDFS. We've run into
this a couple times on our clusters. Once the table is in this state, the only fix is to rm
the znode using the zookeeper-client. Doing this manually looks a bit error prone. Could an
option be added to hbck to catch and fix such inconsistencies?
> A more general issue I'd like comment on is whether it makes sense for HMaster to be
maintaining its own write-ahead log? The idea would be that on a bounce, the master would
discover it was in the middle of creating a table and either rollback or complete that operation?
An issue that we observed recently was that a table that was in DISABLING state before a bounce
was not in that state after. A write-ahead log to persist table state changes seems useful.
Now, all of this state could be in ZK instead of the WAL - it doesn't matter where it gets
persisted as long as it does.

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