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https://issues.apache.org/jira/browse/YARN-3870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15070279#comment-15070279
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Arun Suresh commented on YARN-3870:
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[~leftnoteasy], With respect to the AM, I was thinking.. just having it as a
field in the ReseourceRequest as well as the Container (returned by the
allocate call) would suffice.
>From the perspective of the Scheduler, yes, {{Map = <priority, <id,
><resourceName, request>>>}} was the direction I was thinking.. Correct me if I
>am wrong, but, currently, there is an implicit understanding that all
>resources requests for the same resource requirement should have the same
>priority. Having an explicit request id would allow us to remove that
>constraint as well..
> Providing raw container request information for fine scheduling
> ---------------------------------------------------------------
>
> Key: YARN-3870
> URL: https://issues.apache.org/jira/browse/YARN-3870
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: api, applications, capacityscheduler, fairscheduler,
> resourcemanager, scheduler, yarn
> Reporter: Lei Guo
>
> Currently, when AM sends container requests to RM and scheduler, it expands
> individual container requests into host/rack/any format. For instance, if I
> am asking for container request with preference "host1, host2, host3",
> assuming all are in the same rack rack1, instead of sending one raw container
> request to RM/Scheduler with raw preference list, it basically expand it to
> become 5 different objects with host1, host2, host3, rack1 and any in there.
> When scheduler receives information, it basically already lost the raw
> request. This is ok for single container request, but it will cause trouble
> when dealing with multiple container requests from the same application.
> Consider this case:
> 6 hosts, two racks:
> rack1 (host1, host2, host3) rack2 (host4, host5, host6)
> When application requests two containers with different data locality
> preference:
> c1: host1, host2, host4
> c2: host2, host3, host5
> This will end up with following container request list when client sending
> request to RM/Scheduler:
> host1: 1 instance
> host2: 2 instances
> host3: 1 instance
> host4: 1 instance
> host5: 1 instance
> rack1: 2 instances
> rack2: 2 instances
> any: 2 instances
> Fundamentally, it is hard for scheduler to make a right judgement without
> knowing the raw container request. The situation will get worse when dealing
> with affinity and anti-affinity or even gang scheduling etc.
> We need some way to provide raw container request information for fine
> scheduling purpose.
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