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https://issues.apache.org/jira/browse/MAPREDUCE-4922?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sandy Ryza resolved MAPREDUCE-4922.
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Resolution: Won't Fix
This is the expected behavior
> Request with multiple data local nodes can cause NPE in AppSchedulingInfo
> -------------------------------------------------------------------------
>
> Key: MAPREDUCE-4922
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4922
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: applicationmaster, mr-am, mrv2, scheduler
> Affects Versions: 2.0.2-alpha
> Reporter: Sandy Ryza
> Assignee: Sandy Ryza
>
> With the way that the schedulers work, each request for a container on a node
> must consist of 3 ResourceRequests - one on the node, one on the rack, and
> one with *.
> AppSchedulingInfo tracks the outstanding requests. When a node is assigned a
> node-local container, allocateNodeLocal decrements the outstanding requests
> at each level - node, rack, and *. If the rack requests reach 0, it removes
> the mapping.
> A mapreduce task with multiple data local nodes submits multiple container
> requests, one for each node. It also submits one for each unique rack, and
> one for *. If there are fewer unique racks than data local nodes, this means
> that fewer rack-local ResourceRequests will be submitted than node-local
> ResourceRequests, so the rack-local mapping will be deleted before all the
> node-local requests are allocated and an NPE will come up the next time a
> node-local request from that rack is allocated.
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