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https://issues.apache.org/jira/browse/MAPREDUCE-5329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13752353#comment-13752353
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Avner BenHanoch commented on MAPREDUCE-5329:
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Hi Siddharth,
*Regarding your previous comment:*
{quote}
Isn't the ShuffleToken already specific to a shuffle provider (specifically an
Aux service) - in terms of YARN
{quote}
I don’t think there is an architectural reason for having _shuffleToken_
specific per shuffle provider. *It is safe and reasonable to have one
_shuffleToken_ for all shuffle-providers and for all shuffle-consumers of a
job.*
Looking in the current code, _TaskAttemptImpl_ creates _shuffleToken_ on the
fly for shuffle needs based on the job token and on user credentials. The
_shuffleToken_ is stored in _TokenCache/Credentials map_ under the general
shuffle label _"MapReduceShuffleToken"_.
Also, in the shuffle-consumer side, _shuffleToken_ is part of the ReduceTask
and it is not specific to a shuffle-consumer in any way.
The only thing that may relate _shuffleToken_ to a specific aux-service is an
existing biased in the current code. The code for serializing/deserializing
_shuffleToken_ is located in 2 static methods in the _AuxiliaryService_ class
_ShuffleHandler_. However, I think there is no real justification for that and
it is very easy to move these 2 simple methods to a more appropriate place like
the _Token_ class itself.
*Regarding your current comment:*
{quote}
If the MR AM knows how to handle multiple services, and informs the NM about
all of these, APPLICATION_INIT should just go out to all of them. Sounds like
this jira can be used to fix this?
{quote}
I think that sending _APPLICATION_INIT_ message worth an issue for itself and
fixing it can help a lot several aux-services regardless of any additional fix
for service port (for example aux-services that rely on RDMA and do not use TCP
at all, or aux-services that can read port from conf).
The purpose of the suggested new MAPREDUCE issue is one step further - for
*configuring multiple aux-services* with service-port, regardless of
shuffle-providers and regardless of _APPLICATION_INIT_. Beside, the new issue
is blocked on YARN-1065. Hence, I prefer to fix this little issue without
waiting for a comprehensive fix for all the “neighbor” issues.
Thanks for your help,
Avner
> 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: 2.0.4-alpha
> Reporter: Avner BenHanoch
>
> 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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