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https://issues.apache.org/jira/browse/SPARK-16017?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Shixiong Zhu resolved SPARK-16017.
----------------------------------
          Resolution: Fixed
            Assignee: Shixiong Zhu
       Fix Version/s: 2.0.0
    Target Version/s: 2.0.0  (was: 1.6.2, 2.0.0)

> YarnClientSchedulerBackend now registers backends as IPs instead of Hostnames 
> which causes all tasks to run with RACK_LOCAL locality.
> -------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-16017
>                 URL: https://issues.apache.org/jira/browse/SPARK-16017
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>    Affects Versions: 1.6.2, 2.0.0
>            Reporter: Trystan Leftwich
>            Assignee: Shixiong Zhu
>            Priority: Critical
>             Fix For: 2.0.0
>
>
> Since this change: 
> [SPARK-15395|https://issues.apache.org/jira/browse/SPARK-15395]
> When registering new executor backends it registers them as IPs instead of 
> hostnames. This causes a flow on effect that when the Task manager is trying 
> to figure out what Locality tasks should run at, no tasks can be run At the 
> NODE_LOCAL level.
> This specific call:
> https://github.com/apache/spark/blob/branch-2.0/core/src/main/scala/org/apache/spark/scheduler/TaskSetManager.scala#L886
> [pendingTasksForHost|https://github.com/apache/spark/blob/branch-2.0/core/src/main/scala/org/apache/spark/scheduler/TaskSetManager.scala#L886]
>   are all hostnames pulled from the DFS locations while 
> [hasExecutorsAliveOnHost|https://github.com/apache/spark/blob/9b234b55d1b5e4a7c80e482b3e297bfb8b583a56/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala#L560],
>  uses 
> [executorsByHost|https://github.com/apache/spark/blob/branch-2.0/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala#L98],
>  which are all IP's because they are populated from the RpcAddress.
> As expected this causes significant performance problems, A simple count 
> query will take 22 seconds, But if I revert the change from 
> [SPARK-15395|https://issues.apache.org/jira/browse/SPARK-15395], tasks will 
> run with NODE_LOCAL locality and the same count will take 3 seconds.



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