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From "Sudarshan Kadambi (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-12070) Add an option to hbck to fix ZK inconsistencies
Date Tue, 23 Sep 2014 20:32:34 GMT
Sudarshan Kadambi created HBASE-12070:

             Summary: 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
            Reporter: Sudarshan Kadambi

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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