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https://issues.apache.org/jira/browse/HADOOP-6592?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12837163#action_12837163
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Hong Tang commented on HADOOP-6592:
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bq. Isnt this a duplicate of MAPREDUCE-1227?
No, like Todd mentioned, MAPREDUCE-1227 is for cluster-wide pause. This one is
to pause individual jobs.
There are cases where pausing individual jobs could be desirable. For instance,
I am running a very large job, toward the end I found out some tasks start to
fail due to disk quota limit reached. I'd like to pause the job, free up some
quota space, and resume the job. Pausing a job may also be useful for
debugging.
bq. Unfortunately people do not realize that this has significant (negative)
consequences to the cluster; in particular, map-outputs consume valuable
temporary storage and make this feature un-viable for Map-Reduce.
Agreed. However, the current implementation does not enforce an absolute time
limit of tasks, so the danger of a job holding up temporary storage is still
there if some of its tasks are very slow. Perhaps we should meter a job's
temporary storage usage as the product of data volume and the duration (unit:
"MBxMin"), and set a limit on that. This meter would still be running even if
the job is paused, so tasks or the entire job could be killed if its temp
storage usage quota is reached.
> Scheduler: Pause button desirable
> ---------------------------------
>
> Key: HADOOP-6592
> URL: https://issues.apache.org/jira/browse/HADOOP-6592
> Project: Hadoop Common
> Issue Type: Wish
> Reporter: Adam Kramer
> Priority: Minor
>
> It would be lovely if, from the jobtracker page, I could click a button
> that's not "kill" or "fail" but ..."pause."
> The pause button would stop a certain task from starting any more mappers or
> reducers. They would all wait in the "pending" stage until the job is
> "un-paused." Currently-running tasks would continue to run, and then
> complete, thus freeing the resources for other jobs.
> This would help a lot for systems (esp. Hive) in which one or two jobs are
> hogging a lot of mappers or reducers. The ones they have would finish, and
> then other jobs could "catch up," and then they could be unpaused for a
> while. This would also allow for user-level throttling of their jobs in
> instances where they need a lot of resources but have the time to spare.
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