Jim Brennan created YARN-8656:
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Summary: container-executor should not write cgroup tasks files
for docker containers
Key: YARN-8656
URL: https://issues.apache.org/jira/browse/YARN-8656
Project: Hadoop YARN
Issue Type: Bug
Reporter: Jim Brennan
If cgroups are enabled, we pass the {{--cgroup-parent}} option to {{docker
run}} to ensure that all processes for the container are placed into a cgroup
under (for example) {{/sys/fs/cgroup/cpu/cgroups.hierarchy/container_id}}.
Docker creates a cgroup there with the docker container id as the name and all
of the processes in the container go into that cgroup.
container-executor has code in {{launch_docker_container_as_user()}} that then
cherry-picks the PID of the docker container (usually the launch shell) and
writes that into the
{{/sys/fs/cgroup/cpu/cgroups.hierarchy/container_id/tasks}} file, effectively
moving it from
{{/sys/fs/cgroup/cpu/cgroups.hierarchy/container_id/docker_container_id}} to
{{/sys/fs/cgroup/cpu/cgroups.hierarchy/container_id}}. So you end up with one
process out of the container in the {{container_id}} cgroup, and the rest in
the {{container_id/docker_container_id}} cgroup.
Since we are passing the {{--cgroup-parent}} to docker, there is no need to
manually write the container pid to the tasks file - we can just remove the
code that does this in the docker case.
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