[jira] [Commented] (HBASE-22623) Add RegionObserver coprocessor hook for preWALAppend

["Geoffrey Jacoby (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-22623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16880747#comment-16880747 ] 

Geoffrey Jacoby commented on HBASE-22623:
-----------------------------------------

As an alternative to adding yet-another-new-coprocessor hook, or changing the behavior of an old one, how about this? Complete HBASE-18127, which adds a notion of OperationContext to the ObserverContext for the mutation pipeline. Then add a new field to the OperationContext, WALAttributeMap, which would then allow for _any_ coprocessor hook (before WAL committal) to annotate the WALKey. Then the WAL writing code would just read from the OperationContext and annotate the WALKey appropriately. 

No publicly overridable code would ever get anywhere near a protobuf, and the only interface that would change would be the HBASE-18127 OperationContext one that has never been released. (This would leave as future work the more general cases of HBASE-18127, such as passing information from a RegionObserver to a WALObserver, which prevents use of thread local storage.) 

[~apurtell] [~anoop.hbase][~abhishek.chouhan][~stack]

> Add RegionObserver coprocessor hook for preWALAppend
> ----------------------------------------------------
>
>                 Key: HBASE-22623
>                 URL: https://issues.apache.org/jira/browse/HBASE-22623
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Geoffrey Jacoby
>            Assignee: Geoffrey Jacoby
>            Priority: Major
>
> While many coprocessor hooks expose the WALEdit to implementing coprocs, there aren't any that expose the WALKey before it's created and added to the WALEntry. 
> It's sometimes useful for coprocessors to be able to edit the WALKey, for example to add extended attributes using the fields to be added in HBASE-22622. 



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