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https://issues.apache.org/jira/browse/HBASE-4477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13114003#comment-13114003
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Andrew Purtell commented on HBASE-4477:
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We created the WALObserver coprocessor for this use case. You can build this
simply and unobtrusively with a RegionObserver to get the attributes on the Put
and so something with them, like add to the KV; and then a WALObserver can take
application actions according to the added metadata or otherwise filter it out
so it doesn't affect core.
So my question is why does this need to be in core? Is the WALObserver
insufficient? Is this for <= 0.90?
> Ability for an application to store metadata into the transaction log
> ---------------------------------------------------------------------
>
> Key: HBASE-4477
> URL: https://issues.apache.org/jira/browse/HBASE-4477
> Project: HBase
> Issue Type: Improvement
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: hlogMetadata1.txt
>
>
> mySQL allows an application to store an arbitrary blob along with each
> transaction in its transaction logs. This JIRA is to have a similar feature
> request for HBASE.
> The use case is as follows: An application on one data center A stores a blob
> of data along with each transaction. A replication software picks up these
> blobs from the transaction logs in A and hands it to another instance of the
> same application running on a remote data center B. The application in B is
> responsible for applying this to the remote Hbase cluster (and also handle
> conflict resolution if any).
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