[jira] [Created] (MAPREDUCE-6514) Update ask to indicate to RM that it need not allocate for ramped down reducers

["Varun Saxena (JIRA)" <ji...@apache.org>]

Varun Saxena created MAPREDUCE-6514:
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             Summary: Update ask to indicate to RM that it need not allocate for ramped down reducers
                 Key: MAPREDUCE-6514
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6514
             Project: Hadoop Map/Reduce
          Issue Type: Bug
          Components: applicationmaster
    Affects Versions: 2.7.1
            Reporter: Varun Saxena
            Assignee: Varun Saxena


In RMContainerAllocator#preemptReducesIfNeeded, we simply clear the scheduled reduces map and put these reducers to pending. This is not updated in ask. So RM keeps on assigning and AM is not able to assign as no reducer is scheduled(check logs below the code).
If this is updated immediately, RM will be able to schedule mappers immediately which anyways is the intention when we ramp down reducers.
{code}
 LOG.info("Ramping down all scheduled reduces:"
            + scheduledRequests.reduces.size());
        for (ContainerRequest req : scheduledRequests.reduces.values()) {
          pendingReduces.add(req);
        }
        scheduledRequests.reduces.clear();
{code}




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