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https://issues.apache.org/jira/browse/MAPREDUCE-5329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13780443#comment-13780443
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Siddharth Seth commented on MAPREDUCE-5329:
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bq.  1. you still want "mapreduce.job.shuffle.provider.plugin.classes" (that I 
don't like)
Not sure why you don't like that. This config is being used by the AM, on a per 
job-basis to configure ShuffleProviders that the job will use.

bq. In this case, I don't know how to calculate serviceName from serviceClass. 
I think we'll need to change the config to contain serviceNames instead of 
serviceClasses. Is this what you mean?
Is it possible to at least track which of the configured services have been 
found - i.e. the job wants X & Y, but the NM is only running X. The tracking 
can be independent of how you loop over the services.
                
> APPLICATION_INIT is never sent to AuxServices other than the builtin 
> ShuffleHandler
> -----------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-5329
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5329
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mr-am
>    Affects Versions: 2.1.0-beta, 2.0.6-alpha
>            Reporter: Avner BenHanoch
>             Fix For: trunk
>
>         Attachments: MAPREDUCE-5329.patch
>
>
> APPLICATION_INIT is never sent to AuxServices other than the built-in 
> ShuffleHandler.  This means that 3rd party ShuffleProvider(s) will not be 
> able to function, because APPLICATION_INIT enables the AuxiliaryService to 
> map jobId->userId. This is needed for properly finding the MOFs of a job per 
> reducers' requests.
> NOTE: The built-in ShuffleHandler does get APPLICATION_INIT events due to 
> hard-coded expression in hadoop code. The current TaskAttemptImpl.java code 
> explicitly call: serviceData.put (ShuffleHandler.MAPREDUCE_SHUFFLE_SERVICEID, 
> ...) and ignores any additional AuxiliaryService. As a result, only the 
> built-in ShuffleHandler will get APPLICATION_INIT events.  Any 3rd party 
> AuxillaryService will never get APPLICATION_INIT events.
> I think a solution can be in one of two ways:
> 1. Change TaskAttemptImpl.java to loop on all Auxiliary Services and register 
> each of them, by calling serviceData.put (…) in loop.
> 2. Change AuxServices.java similar to the fix in: MAPREDUCE-2668  
> "APPLICATION_STOP is never sent to AuxServices".  This means that in case the 
> 'handle' method gets APPLICATION_INIT event it will demultiplex it to all Aux 
> Services regardless of the value in event.getServiceID().
> I prefer the 2nd solution.  I am welcoming any ideas.  I can provide the 
> needed patch for any option that people like.
> See [Pluggable Shuffle in Hadoop 
> documentation|http://hadoop.apache.org/docs/current/hadoop-mapreduce-client/hadoop-mapreduce-client-core/PluggableShuffleAndPluggableSort.html]

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