We have seen the following scenario in our cluster:
A job got marked failed, because four attempts of a TIP failed. This would kill all the map and reduce tips. Then a job-cleanup attempt is launched.
The job-cleanup attempt failed because it could not report status for 10 minutes. There are 3 such job-cleanup attempts leading the job to get killed after 1/2 hour.
While waiting for the job cleanup to finish, JobTracker scheduled many tasks of the job on TaskTrackers and sent a KillTaskAction in the next heartbeat.
This is just wasting lots of resources, we should avoid scheduling tasks of a tip once the tip is killed/failed.