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https://issues.apache.org/jira/browse/YARN-8648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16580149#comment-16580149
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Billie Rinaldi commented on YARN-8648:
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I am wondering if this approach would break the docker launching docker use
case. Currently if you're launching a new docker container from an existing
docker container, you can have the new container use the same cgroup as the
first container (e.g. /hadoop-yarn/${CONTAINER_ID}), but if there weren't a
unique cgroup parent for the container you wouldn't be able to do that. Unless
there's a way to find out the docker container id from inside the container?
> 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
> Priority: Major
> Labels: Docker
>
> 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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