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https://issues.apache.org/jira/browse/YARN-4712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15183611#comment-15183611
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Sangjin Lee commented on YARN-4712:
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My main concern with using {{cpuUsageTotalCoresPercentage}} is about
*aggregation*, and I think using {{cpuUsageTotalCoresPercentage}} breaks down
in a heterogeneous cluster. Here is an illustrative example.
Suppose you have a 2-node cluster, where the first node has 4 cores and the
second node has 8 cores. Furthermore, suppose that the container on the 4-core
node is utilizing all 4 cores and the container on the 8-core node is utilizing
1 core. Since the entire cluster has 12 cores and the app is using 5 cores, the
utilization of this app should be 42% (5/12 cores).
However, if we use {{cpuUsageTotalCoresPercentage}}, we have a problem. The
container on the 4-core node will report 100% utilization on that node, and the
other container on the 8-core node will report 12.5% utilization. Then, if we
aggregated the container metrics to the app, the app would have 112.5%
utilization of the cluster or 56% per node. IMO this is not correct, or at best
misleading.
If the node capacity in terms of cores is homogeneous, it does not make a
difference by using either. However, if we have a heterogeneous cluster, the
latter essentially under-weighs larger machines by using *simple* averages.
This would result in a misleading and confusing result on aggregation.
I do recognize using {{cpuUsagePercentPerCore}} would require the total number
of cores for the cluster when aggregated to arrive at a relative percentage
number. But overall I do feel that {{cpuUsagePercentPerCore}} would be a more
accurate measure of the cluster utilization when aggregated.
I am OK with separating that discussion to another JIRA.
> CPU Usage Metric is not captured properly in YARN-2928
> ------------------------------------------------------
>
> Key: YARN-4712
> URL: https://issues.apache.org/jira/browse/YARN-4712
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: timelineserver
> Reporter: Naganarasimha G R
> Assignee: Naganarasimha G R
> Labels: yarn-2928-1st-milestone
> Attachments: YARN-4712-YARN-2928.v1.001.patch,
> YARN-4712-YARN-2928.v1.002.patch, YARN-4712-YARN-2928.v1.003.patch,
> YARN-4712-YARN-2928.v1.004.patch
>
>
> There are 2 issues with CPU usage collection
> * I was able to observe that that many times CPU usage got from
> {{pTree.getCpuUsagePercent()}} is
> ResourceCalculatorProcessTree.UNAVAILABLE(i.e. -1) but ContainersMonitor do
> the calculation i.e. {{cpuUsageTotalCoresPercentage = cpuUsagePercentPerCore
> /resourceCalculatorPlugin.getNumProcessors()}} because of which UNAVAILABLE
> check in {{NMTimelinePublisher.reportContainerResourceUsage}} is not
> encountered. so proper checks needs to be handled
> * {{EntityColumnPrefix.METRIC}} uses always LongConverter but
> ContainerMonitor is publishing decimal values for the CPU usage.
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