Omkar Vinit Joshi created YARN-957:
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             Summary: Capacity Scheduler tries to reserve the memory more than 
what node manager reports.
                 Key: YARN-957
                 URL: https://issues.apache.org/jira/browse/YARN-957
             Project: Hadoop YARN
          Issue Type: Bug
            Reporter: Omkar Vinit Joshi


I have 2 node managers.
* one with 1024 MB memory.(nm1)
* second with 2048 MB memory.(nm2)
I am submitting simple map reduce application with 1 mapper and one reducer 
with 1024mb each. The steps to reproduce this are
* stop nm2 with 2048MB memory.( This I am doing to make sure that this node's 
heartbeat doesn't reach RM first).
* now submit application. As soon as it receives first node's (nm1) heartbeat 
it will try to reserve memory for AM-container (2048MB). However it has only 
1024MB of memory.
* now start nm2 with 2048 MB memory.

It hangs forever... Ideally this has two potential issues.
* It should not try to reserve memory on a node manager which is never going to 
give requested memory. i.e. Current max capability of node manager is 1024MB 
but 2048MB is reserved on it. But it still does that.
* Say 2048MB is reserved on nm1 but nm2 comes back with 2048MB available 
memory. In this case if the original request was made without any locality then 
scheduler should unreserve memory on nm1 and allocate requested 2048MB 
container on nm2.


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