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From "Liu Shaohui (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-11536) Puts of region location to Meta may be out of order which causes inconsistent of region location
Date Thu, 17 Jul 2014 08:04:05 GMT
Liu Shaohui created HBASE-11536:

             Summary: Puts of region location to Meta may be out of order which causes inconsistent
of region location
                 Key: HBASE-11536
                 URL: https://issues.apache.org/jira/browse/HBASE-11536
             Project: HBase
          Issue Type: Bug
          Components: Region Assignment
            Reporter: Liu Shaohui
            Priority: Critical

In product hbase cluster, we found inconsistency of region location in the meta table. Region
cdfa2ed711bbdf054d9733a92fd43eb5 is onlined in regionserver but the region
location in Meta table is
This is because of the out-of-order puts for meta table.

# HMaster try to assign the region to
# RegionServer: During the opening the region, the put of region location(
to meta table is timeout(60s) and the htable retry for second time. (regionserver serving
meta has got the request of the put. The timeout is beause  ther is a bad disk in this regionserver
and sync of hlog is very slow. 
During the retry in htable, the OpenRegionHandler is timeout(100s) and the PostOpenDeployTasksThread
is interrupted. Through the htable is closed in the MetaEditor finally, the share connection
the htable used is not closed and the call of put for meta table is on-flying in the connection.
Assumed that this on-flying call of put to meta is  named call A.
# RegionServer: For the timeout of OpenRegionHandler, the OpenRegionHandler
marks the assign state of this region to FAILED_OPEN.
# HMaster watchs this event of FAILED_OPEN and assigns the region to another regionserver:
# RegionServer: This regionserver opens the region successfully . Assumed
that the put of region location( to meta table in this regionserver is
named B.

There is no order guarantee for call A and B. If call A is processed after call B in regionserver
serving meta region, the region location in meta table will be wrong.

>From the raw scan of meta table we found:
scan '.META.', {RAW => true, LIMIT => 1, VERSIONS => 10, STARTROW => 'xxx.adfa2ed711bbdf054d9733a92fd43eb5.'}


xxx.adfa2ed711bbdf054d9733a92fd43eb5. column=info:server, timestamp=1404885460553(=> Wed
Jul 09 13:57:40 +0800 2014), value= --> Retry put from

xxx.adfa2ed711bbdf054d9733a92fd43eb5. column=info:server, timestamp=1404885456731(=> Wed
Jul 09 13:57:36 +0800 2014), value= --> put from
xxx.adfa2ed711bbdf054d9733a92fd43eb5. column=info:server, timestamp=1404885353122( Wed Jul
09 13:55:53 +0800 2014), value=  --> First put from

Related hbase log is attached in this issue and disscusions are welcomed.

For there is no order guarantee for puts from different htables, one solution for this issue
is to give an increased id for each assignment of a region and use this id as the timestamp
of put of region location to meta table. The region location with large assign id will be
got by hbase clients.

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