[jira] Updated: (HADOOP-4979) Capacity Scheduler does not always return no task to a TT if a job's memry requirements are not met

["Vivek Ratan (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-4979?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vivek Ratan updated HADOOP-4979:
--------------------------------

    Attachment: 4979.1.patch

Simple fix in 4979.1.patch.

> Capacity Scheduler does not always return no task to a TT if a job's memry requirements are not met
> ---------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-4979
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4979
>             Project: Hadoop Core
>          Issue Type: Bug
>            Reporter: Vivek Ratan
>         Attachments: 4979.1.patch
>
>
> As per HADOOP-4035, the Capacity Scheduler should return no task to a TT if a job's high mem requirements are not met. This doesn't always happen. In the Scheduler's assignTasks() method, if a job's map task does not enough memory to run, the Scheduler looks at reduce tasks, and vice-versa. This can result in a case where a reduce task from another job is returned to the TT (if the high-mem job does not have a reduce task to run, for example), thus starving the high-mem job. 

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