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MapReduce, mail # dev - API Design: getClusterMetrics


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Saptarshi Guha 2012-10-10, 04:11
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Re: API Design: getClusterMetrics
Vinod Kumar Vavilapalli 2012-10-10, 19:47

This is to help evolve the APIs easily. All apis have request and response objects, instead of passing in parameters directly. Some of the APIs clearly may not need this extra layer, but doing so helps uniformity.

Irrespective of that, following the original goal, GetClusterMetricsResponse itself could have all the fields, instead of one more nested ClusterMetrics object.

Thanks,
+Vinod

On Oct 9, 2012, at 9:11 PM, Saptarshi Guha wrote:

> Hello
> (sorry for cross post)
> I am reading the DistributedShell code and came across
>
> GetClusterMetricsRequest clusterMetricsReq > Records.newRecord(GetClusterMetricsRequest.class);
> GetClusterMetricsResponse clusterMetricsResp > applicationsManager.getClusterMetrics(clusterMetricsReq);
>
> In the page: http://hadoop.apache.org/docs/current/api/org/apache/hadoop/yarn/api/ClientRMProtocol.html#getClusterMetrics%28org.apache.hadoop.yarn.api.protocolrecords.GetClusterMetricsRequest%29
>
> I can't find any other function getClusterMetrics.
>
> Why was the choice made to pass a GetClusterMetricsRequest object to
> getClusterMetrics?
> why couldn't the programmer invoke
> applicationsManager.getClusterMetrics() and the method would reply
> with a GetClusterMetricsResponse?
>
> Regards
> Sapsi
> (P.S I havent used YARN or even written code with it, i'm just reading
> some sources and my reading is incomplete, so apologies if this comes
> across
> as stupid)

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Robert Evans 2012-10-10, 14:30