Bob created MAPREDUCE-6485:
------------------------------
Summary: MR job hanged forever because all resources are taken up
by reducers and the last map attempt never get resource to run
Key: MAPREDUCE-6485
URL: https://issues.apache.org/jira/browse/MAPREDUCE-6485
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: applicationmaster
Affects Versions: 3.0.0
Reporter: Bob
Priority: Critical
The scenarios is like this:
With configuring mapreduce.job.reduce.slowstart.completedmaps=0.8, reduces will
take resource and start to run when all the map have not finished.
But It could happened that when all the resources are taken up by running
reduces, there is still one map not finished.
Under this condition , the last map have two task attempts .
As for the first attempt was killed due to timeout(mapreduce.task.timeout), and
its state transitioned from RUNNING to FAIL_CONTAINER_CLEANUP, so failed map
attempt would not be started.
As for the second attempt which was started due to having enable map task
speculative is pending at UNASSINGED state because of no resource available.
But the second map attempt request have lower priority than reduces, so
preemption would not happened.
As a result all reduces would not finished because of there is one map left.
and the last map hanged there because of no resource available. so, the job
would never finished.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
