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