[jira] [Created] (YARN-8648) Container cgroups are leaked when using docker

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

Jim Brennan created YARN-8648:
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             Summary: Container cgroups are leaked when using docker
                 Key: YARN-8648
                 URL: https://issues.apache.org/jira/browse/YARN-8648
             Project: Hadoop YARN
          Issue Type: Bug
            Reporter: Jim Brennan
            Assignee: Jim Brennan


When you run with docker and enable cgroups for cpu, docker creates cgroups for all resources on the system, not just for cpu.  For instance, if the {{yarn.nodemanager.linux-container-executor.cgroups.hierarchy=/hadoop-yarn}}, the nodemanager will create a cgroup for each container under {{/sys/fs/cgroup/cpu/hadoop-yarn}}.  In the docker case, we pass this path via the {{--cgroup-parent}} command line argument.   Docker then creates a cgroup for the docker container under that, for instance: {{/sys/fs/cgroup/cpu/hadoop-yarn/container_id/docker_container_id}}.

When the container exits, docker cleans up the {{docker_container_id}} cgroup, and the nodemanager cleans up the {{container_id}} cgroup,   All is good under {{/sys/fs/cgroup/hadoop-yarn}}.

The problem is that docker also creates that same hierarchy under every resource under {{/sys/fs/cgroup}}.  On the rhel7 system I am using, these are: blkio, cpuset, devices, freezer, hugetlb, memory, net_cls, net_prio, perf_event, and systemd.    So for instance, docker creates {{/sys/fs/cgroup/cpuset/hadoop-yarn/container_id/docker_container_id}}, but it only cleans up the leaf cgroup {{docker_container_id}}.  Nobody cleans up the {{container_id}} cgroups for these other resources.  On one of our busy clusters, we found > 100,000 of these leaked cgroups.

I found this in our 2.8-based version of hadoop, but I have been able to repro with current hadoop.




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