Bikas Saha commented on YARN-752:

Its not 100% clear what the API should be on the AMRMClient for specific 
requests. A set of checks need to be made so that unsatisfiable requests cannot 
be made or illegal mix-n-match cannot happen. The server side impl is simple 
and does no checks for the sake of overhead reduction.
Regardless, given the protocol API that requires relaxLocality flag to be 
specified on racks for the specific nodes, the resolution of nodes to racks is 
required, even in that case. This jira is simply for the addition of rack 
resolution functionality to the AMRMClient. Its current use is to make sure all 
nodes are resolved to their racks or else those requests will be unsatisfiable 
on the server side, resulting in correctness issues.

The patch by itself has a bug. After a container request has been removed, it 
should not be returned via getMatchingRequests() for the inferred rack. i.e. 
the patch was doing addResourceRequest() for the inferred rack but not doing 
the corresponding removeResourceRequest(). The simple fix is to resolve/dedupe 
not only during addContainerRequest() but also during removeContainerRequest(). 
Attaching patch with simple fix and minor changes to the javadoc.
> In AMRMClient, automatically add corresponding rack requests for requested 
> nodes
> --------------------------------------------------------------------------------
>                 Key: YARN-752
>                 URL: https://issues.apache.org/jira/browse/YARN-752
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: api, applications
>    Affects Versions: 2.0.4-alpha
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>         Attachments: YARN-752-1.patch, YARN-752-1.patch, YARN-752-2.patch, 
> YARN-752.3.patch, YARN-752.patch
> A ContainerRequest that includes node-level requests must also include 
> matching rack-level requests for the racks that those nodes are on.  When a 
> node is present without its rack, it makes sense for the client to 
> automatically add the node's rack.

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