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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-2195) Support cyclic replication
Date Sun, 04 Sep 2011 23:34:09 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13096967#comment-13096967

Lars Hofhansl commented on HBASE-2195:

OK... Right now I made it versioned by observing the current byte cluster id is always 0,
so I was using this as version byte. I'll look into VersionedWritable.

I also have conditioned code that only writes the 16bytes when needed (at the expense of having
to write an extra boolean).

re: Byte ids... The bytes id is just used locally at a replication source. It has no meaning
elsewhere and never ends in the WAL. Otherwise we have to rethink how one adds and removes
sinks at a source (i.e. how do you identify which sink to remove, unless you like to type
in 16 byte ids). Changing this would also mean that we cannot setup the ZNodes at a replication
before the sink is up - as we cannot get the sinks UUID before it can be reached.
This is actually a fairly clean design (IMHO), as a user at a source can give the sinks numbers.
And these numbers will never clash with the same numbers at another source.

I'll attach a patch later today, which hopefully makes it clear what I have in mind.

> Support cyclic replication
> --------------------------
>                 Key: HBASE-2195
>                 URL: https://issues.apache.org/jira/browse/HBASE-2195
>             Project: HBase
>          Issue Type: Sub-task
>          Components: replication
>            Reporter: Jean-Daniel Cryans
>         Attachments: 2195.txt
> We need to support cyclic replication by using the cluster id of each HlogKey and stop
replicating when it goes back to the original cluster.

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