[jira] [Commented] (HBASE-12070) Add an option to hbck to fix ZK inconsistencies

["Stephen Yuan Jiang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-12070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14288447#comment-14288447 ] 

Stephen Yuan Jiang commented on HBASE-12070:
--------------------------------------------

The patch can be viewed at https://reviews.apache.org/r/30197/ (the base branch is branch-1).

> 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
>            Reporter: Sudarshan Kadambi
>            Assignee: Stephen Yuan Jiang
>
> 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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