[jira] Created: (MAPREDUCE-802) Simplify the job updated event notification between Jobtracker and schedulers

["Hemanth Yamijala (JIRA)" <ji...@apache.org>]

Simplify the job updated event notification between Jobtracker and schedulers
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                 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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