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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4210) Allow coprocessor to interact with batches per region sent from a client
Date Tue, 16 Apr 2013 03:48:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4210?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13632541#comment-13632541
] 

Anoop Sam John commented on HBASE-4210:
---------------------------------------

Himanshu
The postBatchMutate will be called before the MVCC completion step. We can not release the
updateLock.readLock before the MVCC completion.
What we make is a way to achieve cross region atomic operation.  The postBatch writes to another
region, but any reader will either see both region data or none.  That was the consideration
in placing the hooks.
Yes you are correct, the updateLock can block the flush requests. But we can ideally not expecting
too time taking ops in these hooks.  I mailing list we can see some people try making RPC
calls from CP hooks (HTable#put()  etc)  It is explained in replies that this is some thing
should be avoided and Andrew explained why it is an anti pattern.  May be we should document
this some where? 
                
> Allow coprocessor to interact with batches per region sent from a client
> ------------------------------------------------------------------------
>
>                 Key: HBASE-4210
>                 URL: https://issues.apache.org/jira/browse/HBASE-4210
>             Project: HBase
>          Issue Type: New Feature
>    Affects Versions: 0.94.6, 0.95.0
>            Reporter: Lars Hofhansl
>            Assignee: Anoop Sam John
>             Fix For: 0.98.0, 0.94.6, 0.95.0
>
>         Attachments: 4210_Trunk-V3.patch, HBASE-4210_94.patch, HBASE-4210_94-V2.patch,
HBASE-4210_94-V3.patch, HBASE-4210_94-V4.patch, HBASE-4210_94-V5.patch, hbase-4210-addendum.patch,
HBASE-4210_Trunk.patch, HBASE-4210_Trunk-V2.patch, HBASE-4210_Trunk-V3.patch
>
>
> Currently the coprocessor write hooks - {pre|post}{Put|Delete} - are strictly one row|cell
operations.
> It might be a good idea to allow a coprocessor to deal with batches of puts and deletes
as they arrive from the client.

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