Wangda Tan created MAPREDUCE-6689:
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Summary: MapReduce job can infinitely increasing number of reducer
resource requests
Key: MAPREDUCE-6689
URL: https://issues.apache.org/jira/browse/MAPREDUCE-6689
Project: Hadoop Map/Reduce
Issue Type: Bug
Reporter: Wangda Tan
Assignee: Wangda Tan
Priority: Blocker
We have seen this issue from one of our clusters: when running terasort
map-reduce job, some mappers failed after reducer started, and then MR AM tries
to preempt reducers to schedule these failed mappers.
After that, MR AM enters an infinite loop, for every
RMContainerAllocator#heartbeat run, it:
- In {{preemptReducesIfNeeded}}, it cancels all scheduled reducer requests.
(total scheduled reducers = 1024)
- Then, in {{scheduleReduces}}, it ramps up all reducers (total = 1024).
As a result, we can see total #requested-containers increased 1024 for every
MRAM-RM heartbeat (1 sec per heartbeat). The AM is hanging for 18+ hours, so we
get 18 * 3600 * 1024 ~ 66M+ requested containers in RM side.
And this bug also triggered YARN-4844, which makes RM stop scheduling anything.
Thanks to [~sidharta-s] for helping with analysis.
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