[jira] Commented: (HADOOP-3687) Ability to pause/resume tasks

["Chris Smith (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3687?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12610258#action_12610258 ] 

Chris Smith commented on HADOOP-3687:
-------------------------------------

I've started work on a way to do this. At the minute it allows reduce tasks to be manually paused and resumed from the command line. The paused/unpaused state of a task is included as a second boolean in the return value of the statusUpdate/ping methods of the umbilical protocol, which isn't particularly elegant but works well enough. Paused tasks sit in a sleep loop waiting to be unpaused (this obviously means that they're consuming resources while not actually doing anything useful — the ideal solution would be to store them somewhere and resume later, as described in HADOOP-91).

Suggestions for improvements/comments welcome...

> Ability to pause/resume tasks
> -----------------------------
>
>                 Key: HADOOP-3687
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3687
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>            Reporter: Chris Smith
>            Priority: Minor
>
> It would be nice to be able to pause (and subsequently resume) tasks that are currently running, in order to allow tasks from higher priority jobs to execute. At present it is quite easy for long-running tasks from low priority jobs to block a task from a newer high priority job, and there is no way to force the execution of the high priority task without killing the low priority jobs.

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