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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3304) ResourceCalculatorProcessTree#getCpuUsagePercent default return value is inconsistent with other getters
Date Tue, 24 Mar 2015 18:45:53 GMT

    [ https://issues.apache.org/jira/browse/YARN-3304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14378354#comment-14378354
] 

Karthik Kambatla commented on YARN-3304:
----------------------------------------

Thought a little more about this. If we choose to go with returning 0 and adding boolean methods
for availability, I would like to see how the corresponding user code will look like compared
to returning -1. 

Do we expect the code to be the following? If so, how do we handle the usage being available
at the time of calling isAvailable, and not being available at the time of calling getUsage?
To avoid this issue, we could get the usage on the availability call and cache it, and the
getUsage call would return this cached value? But, requiring the availability call now is
an even more incompatible change, no? 
{code}
ResourceTrackerProcessTee procTree = new <>();
if (procTree.isMemoryUsageAvailable()) {
  procTree.getMemoryUsage();
}
{code}

And, how is the above user code snippet different from the one below: 
{code}
ResourceTrackerProcessTee procTree = new <>();
procTree.getMemoryUsage();
{code}

What is the cost of breaking compat of this previously Private API? I have a feeling it would
be worth not making the API super-complicated. 

I want to avoid fixing this in a hurry just to unblock the release. I am willing to prioritize
this, chat offline if need be, and solve it the right way. If we think that is too slow, we
could always revert YARN-3296 for 2.7.

> ResourceCalculatorProcessTree#getCpuUsagePercent default return value is inconsistent
with other getters
> --------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-3304
>                 URL: https://issues.apache.org/jira/browse/YARN-3304
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: nodemanager
>            Reporter: Junping Du
>            Assignee: Karthik Kambatla
>            Priority: Blocker
>         Attachments: YARN-3304-v2.patch, YARN-3304.patch
>
>
> Per discussions in YARN-3296, getCpuUsagePercent() will return -1 for unavailable case
while other resource metrics are return 0 in the same case which sounds inconsistent.



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