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https://issues.apache.org/jira/browse/MAPREDUCE-5381?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13791002#comment-13791002
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Luke Lu commented on MAPREDUCE-5381:
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Instead of adding a new decommission API and more code in JT, another more
compatible way would be doing this all in the client using MAPREDUCE-4900 as a
sub-command/option ({{\-\-graceful}} and optionally {{\-\-timeout}}) of
{{--refreshNodes}}, such that the admin client sets the target TTs' slots to 0
and wait for running tasks/jobs metrics to become zero or timeout and then call
the {{refreshNodes}} API.
> Support graceful decommission of tasktracker
> --------------------------------------------
>
> Key: MAPREDUCE-5381
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5381
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mrv1
> Affects Versions: 1.2.0
> Reporter: Luke Lu
> Assignee: Binglin Chang
> Attachments: MAPREDUCE-5381-graceful-decomm.v1.patch
>
>
> When TTs are decommissioned for non-fault reasons (capacity change etc.),
> it's desirable to minimize the impact to running jobs.
> Currently if a TT is decommissioned, all running tasks on the TT need to be
> rescheduled on other TTs. Further more, for finished map tasks, if their map
> output are not fetched by the reducers of the job, these map tasks will need
> to be rerun as well.
> We propose to introduce a mechanism to optionally gracefully decommission a
> tasktracker.
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