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https://issues.apache.org/jira/browse/HBASE-15575?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15221710#comment-15221710
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Matteo Bertozzi commented on HBASE-15575:
-----------------------------------------

I think for 2.0 we can break coprocessor API. 
but if we do so, at least we should do something that make sense. 

the name Procedure does not have any meaning. 
Handler was describing that the operation pre/post was running on a handler and 
not on the main/rpc thread.

If we change the coprocessor API we should consider a better semantic. see 
HBASE-6992
pre/postOperation doesn't do what the user want because the post is not really 
post.

our execution in genereal is
 * pre operation (rpc thread)
 * submit operation 
 * post operation (rpc thread)
 * [pre operation (handler thread)]
 * [post operation (handler thread)]

for the user the pre and post should probably be the actual pre/post. 
which means pre (rpc thread) and post (handler thread).

also, today on failure we don't have a post operation. 
which means that if someone does something in the pre operation there is no way 
to rollback that on failure.
so, we should add something like a "post operation failure"

> Rename table DDL *Handler methods in MasterObserver to *Procedure
> -----------------------------------------------------------------
>
>                 Key: HBASE-15575
>                 URL: https://issues.apache.org/jira/browse/HBASE-15575
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Coprocessors
>    Affects Versions: 2.0.0
>            Reporter: Stephen Yuan Jiang
>            Assignee: Stephen Yuan Jiang
>            Priority: Minor
>             Fix For: 2.0.0
>
>         Attachments: HBASE-15575.v1-master.patch
>
>
> Procedure V2 replaced table DDL handler implementation to procedure 
> implementation.  It does not make sense to keep the *Handler methods in 
> MasterObserver.  This JIRA follows HBASE-13645 way to deprecate the existing 
> observers with *Handler and add the new observers with *Procedure name.



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