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https://issues.apache.org/jira/browse/HBASE-18898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16185234#comment-16185234
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Appy commented on HBASE-18898:
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The only way i can think of to do this is:
Say we want to do this for MasterObserver
- In MasterCPHost, do reflection over MasterObserver, get all its methods and
make a map.
- As CPs are loaded, check all the methods in their observer
- If and only if
- The method signature matches one from MasterObserver
- The method is non-default
Mark that we have a CP overriding that method
- In the hook wrappers we have in MasterCPHost, (and this is the ugly part) do
a reflection to check if any CP is using that hook.
> 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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