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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HBASE-18898) Provide way for the core flow to know whether CP implemented each of the hooks
Date Mon, 16 Oct 2017 22:11:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16206666#comment-16206666
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Andrew Purtell edited comment on HBASE-18898 at 10/16/17 10:10 PM:
-------------------------------------------------------------------

I agree with [~mdrob] comments above. Often in JAX-RS programming you can use one method to
implement for multiple annotations. The flexibility is attractive. I also agree it's nice
not to need required method signatures. Most of our CP compat breaks have been addition of
methods to interfaces or modification of method signatures. Both types of incompatibility
would be much less likely to occur. We would implement the wiring up of code to framework
guided by annotations and variations in the shape of interface/classes and method signatures
would not be a concern any longer. The long term maintenance burdens for both us and implementers
would be lessened. I also agree that annotating method parameters and wiring them up may be
a step too far without a real DI framework, but we should still look into it. 


was (Author: apurtell):
I agree with [~mdrob] comments above. Often in JAX-RS programming you can use one method to
implement for multiple annotations. The flexibility is attractive. I also agree it's nice
not to need required method signatures. Most of our CP compat breaks have been addition of
methods or modification of method signatures. Both types of incompatibility would be much
less likely to occur. The long term maintenance burdens for both us and implementers would
be lessened. I also agree that annotating method parameters and wiring them up may be a step
too far without a real DI framework, but we should still look into it. 

> Provide way for the core flow to know whether CP implemented each of the hooks
> ------------------------------------------------------------------------------
>
>                 Key: HBASE-18898
>                 URL: https://issues.apache.org/jira/browse/HBASE-18898
>             Project: HBase
>          Issue Type: Improvement
>          Components: Coprocessors, Performance
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>            Priority: Critical
>
> This came as a discussion topic at the tale of HBASE-17732
> Can we have a way in the code (before trying to call the hook) to know whether the user
has implemented one particular hook or not? eg: On write related hooks only prePut() might
be what the user CP implemented. All others are just dummy impl from the interface. Can we
have a way for the core code to know this and avoid the call to other dummy hooks fully? Some
times we do some processing for just calling CP hooks (Say we have to make a POJO out of PB
object for calling) and if the user CP not impl this hook, we can avoid this extra work fully.
The pain of this will be more when we have to later deprecate one hook and add new. So the
dummy impl in new hook has to call the old one and that might be doing some extra work normally.
> If the CP f/w itself is having a way to tell this, the core code can make use. What am
expecting is some thing like in PB way where we can call 
> CPObject.hasPreXXXX(), then CPObject. preXXXX ().. Should not like asking users to impl
this extra ugly thing. When the CP instance is loaded in the RS/HM, that object will be having
this info also. 



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