[jira] [Commented] (HBASE-5203) Group atomic put/delete operation into a single WALEdit to handle region server failures.

["Lars Hofhansl (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-5203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13186628#comment-13186628 ] 

Lars Hofhansl commented on HBASE-5203:
--------------------------------------

The refactoring is in the Put/Delete code, not in the replication code, so I don't think it needs another jira, actually.
                
> Group atomic put/delete operation into a single WALEdit to handle region server failures.
> -----------------------------------------------------------------------------------------
>
>                 Key: HBASE-5203
>                 URL: https://issues.apache.org/jira/browse/HBASE-5203
>             Project: HBase
>          Issue Type: Sub-task
>          Components: client, coprocessors, regionserver
>            Reporter: Lars Hofhansl
>             Fix For: 0.94.0
>
>
> HBASE-3584 does not not provide fully atomic operation in case of region server failures (see explanation there).
> What should happen is that either (1) all edits are applied via a single WALEdit, or (2) the WALEdits are applied in async mode and then sync'ed together.
> For #1 it is not clear whether it is advisable to manage multiple *different* operations (Put/Delete) via a single WAL edit. A quick check reveals that WAL replay on region startup would work, but that replication would need to be adapted. The refactoring needed would be non-trivial.
> #2 Might actually not work, as another operation could request sync'ing a later edit and hence flush these entries out as well.

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