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From "Vasu Mariyala (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-7709) Infinite loop possible in Master/Master replication
Date Sat, 24 Aug 2013 00:19:55 GMT

     [ https://issues.apache.org/jira/browse/HBASE-7709?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vasu Mariyala updated HBASE-7709:
---------------------------------

    Attachment: HBASE-7709-rev5.patch
                0.95-trunk-rev4.patch

Attaching the patches 0.95-trunk-rev4.patch (0.95 and trunk) which stores the clusters as
a list rather than set. The first cluster id in the list is the originating cluster and the
subsequent entries indicate replication path.

The patch HBASE-7709-rev5.patch (0.94) has the changes to ensure the api of 0.94 is the same
as the api of 0.95 and trunk.

These patches primarily address the monitoring issues mentioned by [~jeffreyz]
                
> 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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