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https://issues.apache.org/jira/browse/YARN-5849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15648465#comment-15648465
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Miklos Szegedi commented on YARN-5849:
--------------------------------------

Thank you for the comment [~bibinchundatt]!

1. The patch applies to the scenario, when enable mount is false. The group is 
created in other cases. The current implementation throws an exception if any 
controller does not have the group created and writable. What is your more 
specific concern?
2. If I put the line into the else branch, we would miss the ret.put call in 
case the group was just created. I could put ret.put inside both branches, but 
that would make the code more complicated I think. Does this answer your 
concern?

> Automatically create YARN control group for pre-mounted cgroups
> ---------------------------------------------------------------
>
>                 Key: YARN-5849
>                 URL: https://issues.apache.org/jira/browse/YARN-5849
>             Project: Hadoop YARN
>          Issue Type: Improvement
>    Affects Versions: 2.7.3, 3.0.0-alpha1, 3.0.0-alpha2
>            Reporter: Miklos Szegedi
>            Assignee: Miklos Szegedi
>            Priority: Minor
>         Attachments: YARN-5849.000.patch, YARN-5849.001.patch
>
>
> Yarn can be launched with linux-container-executor.cgroups.mount set to 
> false. It will search for the cgroup mount paths set up by the administrator 
> parsing the /etc/mtab file. You can also specify 
> resource.percentage-physical-cpu-limit to limit the CPU resources assigned to 
> containers.
> linux-container-executor.cgroups.hierarchy is the root of the settings of all 
> YARN containers. If this is specified but not created YARN will fail at 
> startup:
> Caused by: java.io.FileNotFoundException: 
> /cgroups/cpu/hadoop-yarn/cpu.cfs_period_us (Permission denied)
> org.apache.hadoop.yarn.server.nodemanager.util.CgroupsLCEResourcesHandler.updateCgroup(CgroupsLCEResourcesHandler.java:263)
> This JIRA is about automatically creating YARN control group in the case 
> above. It reduces the cost of administration.



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