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https://issues.apache.org/jira/browse/MAPREDUCE-6529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14983155#comment-14983155
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Wei Chen commented on MAPREDUCE-6529:
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Yes, What I am doing is just to let MA have chances to choose the containers
it needs. I knows that a delay scheduling is implemented in YARN. It is very
useful for locality sensitive job like MapReduce. But sometimes delay scheduler
can not make sure the optimal resource the AM get. For example, in a
heterogeneous cluster, reduce task may prefer a container on powerful machine
with higher I/O speed. MPI job may prefer containers on machine with higher
cpu frequency. But RM can't know all the resource requirement for different
applications. So I am just wandering if the RPC protocol between RM and AM
may provide such new interface, let the AM make a second choice about if AM
will use the container it just gets. And different AMs may implement their own
preference for container they request.
> AppMaster will not retry to request resource if AppMaster happens to decide
> to not use the resource
> ---------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6529
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6529
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mr-am
> Affects Versions: 2.6.0
> Reporter: Wei Chen
>
> I am viewing code in RMContainerAllocator.java. I want to do some
> improvement so that the AppMaster could give up some containers that may not
> be optimal when it receives new assigned containers. But I found that if
> AppMaster give up the containers, it will not retry to request the resource
> again.
> int RMContainerRequestor.java, Set<ResourceRequest> ask is used to ask
> resource from ResourceManager. I found each container could only be requested
> once. It mean ask can be filled by addResourceRequestToAsk(ResourceRequest
> remoteRequest[]), but it can only added for once for each container. If we
> give up one assigned container, It will never request again
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