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From "Heng Chen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14004) [Replication] Inconsistency between Memstore and WAL may result in data in remote cluster that is not in the origin
Date Wed, 28 Oct 2015 09:19:28 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14978038#comment-14978038
] 

Heng Chen commented on HBASE-14004:
-----------------------------------

On the assumption that HDFS sync successfully and do response,  
but RS NOT get this response because of network disconnect.  As for RS, sync timeout but data
persisted on HDFS.  [~carp84]  

As [~Apache9] mentioned, 
{quote}
A simple solution is killing the regionserver when we fail to sync WAL which means we will
never rollback memstore but reconstruct it using WAL.
{quote} 
It may cause two problems.
 * we may do mutation twice,  (it seems no problems if mutation is incr/append in current
logic?)
 * All RS will be killed if network between RS and NN disconnected shortly.

> [Replication] Inconsistency between Memstore and WAL may result in data in remote cluster
that is not in the origin
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-14004
>                 URL: https://issues.apache.org/jira/browse/HBASE-14004
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>            Reporter: He Liangliang
>            Priority: Critical
>              Labels: replication, wal
>
> Looks like the current write path can cause inconsistency between memstore/hfile and
WAL which cause the slave cluster has more data than the master cluster.
> The simplified write path looks like:
> 1. insert record into Memstore
> 2. write record to WAL
> 3. sync WAL
> 4. rollback Memstore if 3 fails
> It's possible that the HDFS sync RPC call fails, but the data is already  (may partially)
transported to the DNs which finally get persisted. As a result, the handler will rollback
the Memstore and the later flushed HFile will also skip this record.



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