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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