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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-4177) Handling read failures during recovery‏ - when HMaster calls Namenode recovery, recovery may be a failure leading to read failure while splitting logs
Date Mon, 08 Aug 2011 17:50:27 GMT
Handling read failures during recovery‏ - when HMaster calls Namenode recovery, recovery
may be a failure leading to read failure while splitting logs
------------------------------------------------------------------------------------------------------------------------------------------------------

                 Key: HBASE-4177
                 URL: https://issues.apache.org/jira/browse/HBASE-4177
             Project: HBase
          Issue Type: Bug
          Components: master
            Reporter: ramkrishna.s.vasudevan
            Assignee: ramkrishna.s.vasudevan


As per the mailing thread with the heading
'Handling read failures during recovery‏' we found this problem.
As part of split Logs the HMaster calls Namenode recovery.  The recovery is an asynchronous
process. 
In HDFS
=======
Even though client is getting the updated block info from Namenode on first
read failure, client is discarding the new info and using the old info only
to retrieve the data from datanode. So, all the read
retries are failing. [Method parameter reassignment - Not reflected in
caller]. 
In HBASE
=======
In HMaster code we tend to wait for  1sec.  But if the recovery had some failure then split
log may not happen and may lead to dataloss.
So may be we need to decide upon the actual delay that needs to be introduced once Hmaster
calls NN recovery.



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