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https://issues.apache.org/jira/browse/YARN-1372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14130554#comment-14130554
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Anubhav Dhoot commented on YARN-1372:
-------------------------------------

>why adding context.getContainers().remove(cid); in 
>removeVeryOldStoppedContainersFromContext method? won’t this remove the 
>containers from context immediately when we send the container statuses 
>across, which contradicts the rest of the changes?

two reasons. 
1) To enforce a timeout for the context entries as a safety net (this should 
happen only after the timeout which is defaulted to 10 min). Otherwise I am 
worried there will be cases where the entries do not get removed for a long 
time. Is is possible that for some reason there is no ack from AM and the 
application never gets removed and these entries stay in memory? 
2) If we are removing it from the nm store, is there any value in keeping it in 
memory? If NM restarts, its not going to know about this anyway.  

> Ensure all completed containers are reported to the AMs across RM restart
> -------------------------------------------------------------------------
>
>                 Key: YARN-1372
>                 URL: https://issues.apache.org/jira/browse/YARN-1372
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: resourcemanager
>            Reporter: Bikas Saha
>            Assignee: Anubhav Dhoot
>         Attachments: YARN-1372.001.patch, YARN-1372.001.patch, 
> YARN-1372.002_NMHandlesCompletedApp.patch, 
> YARN-1372.002_RMHandlesCompletedApp.patch, 
> YARN-1372.002_RMHandlesCompletedApp.patch, YARN-1372.003.patch, 
> YARN-1372.prelim.patch, YARN-1372.prelim2.patch
>
>
> Currently the NM informs the RM about completed containers and then removes 
> those containers from the RM notification list. The RM passes on that 
> completed container information to the AM and the AM pulls this data. If the 
> RM dies before the AM pulls this data then the AM may not be able to get this 
> information again. To fix this, NM should maintain a separate list of such 
> completed container notifications sent to the RM. After the AM has pulled the 
> containers from the RM then the RM will inform the NM about it and the NM can 
> remove the completed container from the new list. Upon re-register with the 
> RM (after RM restart) the NM should send the entire list of completed 
> containers to the RM along with any other containers that completed while the 
> RM was dead. This ensures that the RM can inform the AM's about all completed 
> containers. Some container completions may be reported more than once since 
> the AM may have pulled the container but the RM may die before notifying the 
> NM about the pull.



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