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.