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https://issues.apache.org/jira/browse/MAPREDUCE-802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12735033#action_12735033
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Vinod K V commented on MAPREDUCE-802:
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+10 for simplifying/fixing the contract.
> Simplify the job updated event notification between Jobtracker and schedulers
> -----------------------------------------------------------------------------
>
> Key: MAPREDUCE-802
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-802
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: jobtracker
> Reporter: Hemanth Yamijala
>
> HADOOP-4053 and HADOOP-4149 added events to take care of updates to the state
> / property of a job like the run state / priority of a job notified to the
> scheduler. We've seen some issues with this framework, such as the following:
> - Events are not raised correctly at all places. If a new code path is added
> to kill a job, raising events is missed out.
> - Events are raised with incorrect event data. For e.g. typically start time
> value is missed out.
> The resulting contract break between jobtracker and schedulers has lead to
> problems in the capacity scheduler where jobs remain stuck in the queue
> without being ever removed and so on.
> It has proven complicated to get this right in the framework and fixes have
> typically still left dangling cases. Or new code paths introduce new bugs.
> This JIRA is about trying to simplify the interaction model so that it is
> more robust and works well.
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