[jira] [Created] (YARN-8031) NodeManager will fail to start if cpu subsystem is already mounted

["JayceAu (JIRA)" <ji...@apache.org>]

JayceAu created YARN-8031:
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             Summary: NodeManager will fail to start if cpu subsystem is already mounted
                 Key: YARN-8031
                 URL: https://issues.apache.org/jira/browse/YARN-8031
             Project: Hadoop YARN
          Issue Type: Bug
          Components: nodemanager
    Affects Versions: 2.5.0
            Reporter: JayceAu
         Attachments: image-2018-03-15-14-47-30-583.png

if *yarn.nodemanager.linux-container-executor.cgroups.mount* is set to true and cpu subsystem is not yet mounted, NodeManager will mount the cpu subsystem and then create the control group whose default name is *hadoop-yarn* if the mount step is successful. This procedure works well if cpu subsystem is not yet mounted. However, under some situation cpu subsystem is already mounted before NodeManager starts and NodeManager will fail to start because of no write permission to the *hadoop-yarn* path . For example:
 # in OS that use systemd such as centos7 will have cpu subsystem mounted by default on machine startup
 # some deamon whose start order is more precedent than NodeManager may also rely on the mounted state of cpu subsystem. In our production environment, we limit the cpu usage of the monitoring and control agent, which starts on reboot

In order to solve this problem, container-executor must be able to create the control group *hadoop-yarn* if mounting controller is successful or this controller is already mounted. Besides, if cpu subsystem is used in combination with other subsystem and it's already mounted, container-executor should use the latest mount point of cpu subsystem instread of the one provided by NodeManager.



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