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https://issues.apache.org/jira/browse/HBASE-7709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13736398#comment-13736398
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Jeffrey Zhong commented on HBASE-7709:
--------------------------------------
[~vasu.mariy...@gmail.com] I reviewed your patch. The following lines:
{code}
- if (!logKey.getClusterId().equals(peerClusterId)) {
+ // don't replicate if the log entries has already been consumed by the
peer cluster
+ if (!edit.hasClusterConsumed(peerClusterId)) {
{code}
I think we still need keep the old check around. The above change may cause
issues during upgrade. For example, we have ( A -> B, B-> A) replication setup.
If we just upgrade cluster A, the above change may cause infinite loop before
we upgrade cluster B.
Rest code looks good to me.
> 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
> Fix For: 0.98.0, 0.95.2, 0.94.12
>
> Attachments: HBASE-7709.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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