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