[jira] [Commented] (YARN-1127) reservation exchange and excess reservation is not working for capacity scheduler

["Bikas Saha (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-1127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13755090#comment-13755090 ] 

Bikas Saha commented on YARN-1127:
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Isnt this similar to a jira opened by you already? The issue being that the scheduler puts a reservation on a node whose total capacity is smaller than the reservation resource size. In this case, nm1 has capacity=1024 but the scheduler is putting a reservation of 2048 on it and that can never be satisfied. So it does not make sense to make that reservation at all.
                
> reservation exchange and excess reservation is not working for capacity scheduler
> ---------------------------------------------------------------------------------
>
>                 Key: YARN-1127
>                 URL: https://issues.apache.org/jira/browse/YARN-1127
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 2.1.1-beta
>            Reporter: Omkar Vinit Joshi
>            Assignee: Omkar Vinit Joshi
>            Priority: Blocker
>
> I have 2 node managers.
> * one with 1024 MB memory.(nm1)
> * second with 2048 MB memory.(nm2)
> I am submitting simple map reduce application with 1 mapper and one reducer with 1024mb each. The steps to reproduce this are
> * stop nm2 with 2048MB memory.( This I am doing to make sure that this node's heartbeat doesn't reach RM first).
> * now submit application. As soon as it receives first node's (nm1) heartbeat it will try to reserve memory for AM-container (2048MB). However it has only 1024MB of memory.
> * now start nm2 with 2048 MB memory.
> It hangs forever... Ideally this has two potential issues.
> * Say 2048MB is reserved on nm1 but nm2 comes back with 2048MB available memory. In this case if the original request was made without any locality then scheduler should unreserve memory on nm1 and allocate requested 2048MB container on nm2. 
> * We support a notion where if say we have 5 nodes with 4 AM and all node managers have 8GB each and AM 2 GB each. Each AM is requesting 8GB each. Now to avoid deadlock AM will make an extra reservation. By doing this we would never hit the deadlock situation.

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