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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7709) Infinite loop possible in Master/Master replication
Date Sun, 25 Aug 2013 07:13:57 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13749550#comment-13749550
] 

Hadoop QA commented on HBASE-7709:
----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12599751/HBASE-7709-rev5.patch
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:green}+1 tests included{color}.  The patch appears to include 3 new or modified
tests.

    {color:red}-1 patch{color}.  The patch command could not apply the patch.

Console output: https://builds.apache.org/job/PreCommit-HBASE-Build/6866//console

This message is automatically generated.
                
> Infinite loop possible in Master/Master replication
> ---------------------------------------------------
>
>                 Key: HBASE-7709
>                 URL: https://issues.apache.org/jira/browse/HBASE-7709
>             Project: HBase
>          Issue Type: Bug
>          Components: Replication
>    Affects Versions: 0.94.6, 0.95.1
>            Reporter: Lars Hofhansl
>            Assignee: Vasu Mariyala
>             Fix For: 0.98.0, 0.94.12, 0.96.0
>
>         Attachments: 095-trunk.patch, 0.95-trunk-rev1.patch, 0.95-trunk-rev2.patch, 0.95-trunk-rev3.patch,
0.95-trunk-rev4.patch, HBASE-7709.patch, HBASE-7709-rev1.patch, HBASE-7709-rev2.patch, HBASE-7709-rev3.patch,
HBASE-7709-rev4.patch, HBASE-7709-rev5.patch
>
>
>  We just discovered the following scenario:
> # Cluster A and B are setup in master/master replication
> # By accident we had Cluster C replicate to Cluster A.
> Now all edit originating from C will be bouncing between A and B. Forever!
> The reason is that when the edit come in from C the cluster ID is already set and won't
be reset.
> We have a couple of options here:
> # Optionally only support master/master (not cycles of more than two clusters). In that
case we can always reset the cluster ID in the ReplicationSource. That means that now cycles
> 2 will have the data cycle forever. This is the only option that requires no changes
in the HLog format.
> # Instead of a single cluster id per edit maintain a (unordered) set of cluster id that
have seen this edit. Then in ReplicationSource we drop any edit that the sink has seen already.
The is the cleanest approach, but it might need a lot of data stored per edit if there are
many clusters involved.
> # Maintain a configurable counter of the maximum cycle side we want to support. Could
default to 10 (even maybe even just). Store a hop-count in the WAL and the ReplicationSource
increases that hop-count on each hop. If we're over the max, just drop the edit.

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