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https://issues.apache.org/jira/browse/MAPREDUCE-5505?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13771233#comment-13771233
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Zhijie Shen commented on MAPREDUCE-5505:
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bq. I dont think making jobimpl aware of all this is a good idea.
The reason to make JobImpl to be aware of unregister is that JobImpl#getState()
needs the info to decide whether it returns the final state (SUCCEEDED, FAILED,
KILLED, ERROR) or the prior state (RUNNING). JobImpl#getState() is called by
not only getReport() but also JobInfo. As I mentioned above, I did this in
getState() to ensure client protocol and web UI can see the consistent state.
Therefore, in this case, we can move the getReport() JobImpl ->
MRClientService, but it is not necessary.
bq. MRClientService is already the last thing to stop. So its a good place to
contain this race condition handling logic.
+1. Agree it's a good place. When MRAppMaster#serviceStop is called,
RMCommunicator#serviceStop is called before MRClientService#serviceStop, where
unregister has already been executed. Therefore after this execution, it's
already safe to notify the client/webUI of the final state of the job, because
one AM has exact one job.
> Clients should be notified job finished only after job successfully
> unregistered
> ---------------------------------------------------------------------------------
>
> Key: MAPREDUCE-5505
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5505
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Jian He
> Assignee: Zhijie Shen
> Attachments: MAPREDUCE-5505.1.patch, MAPREDUCE-5505.1.patch
>
>
> This is to make sure user is notified job finished after job is really done.
> This does increase client latency but can reduce some races during unregister
> like YARN-540
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