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docs: troubleshoot high memory usage (#810)

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On some OS, high ulimit causes some container to use a lot of memory. We
do not attempt to resolve this issue in Tutor because this is a
mysql/uwsgi issue. Instead, we explain how to resolve it in the
troubleshooting docs.

Close #671.
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Régis Behmo 2023-03-10 11:20:21 +01:00 committed by GitHub
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@ -112,6 +112,34 @@ You can identify which containers are consuming most resources by running::
docker stats
In idle mode, the "mysql" container should use ~200MB memory; ~200-300MB for the the "lms" and "cms" containers.
On some operating systems, such as RedHat, Arch Linux or Fedora, a very high limit of the number of open files (``nofile``) per container may cause the "mysql", "lms" and "cms" containers to use a lot of memory: up to 8-16GB. To check whether you might impacted, run::
cat /proc/$(pgrep dockerd)/limits | grep "Max open files"
If the output is 1073741816 or higher, then it is likely that you are affected by `this mysql issue <https://github.com/docker-library/mysql/issues/579>`__. To learn more about the root cause, read `this containerd issue comment <https://github.com/containerd/containerd/pull/7566#issuecomment-1285417325>`__. Basically, the OS is hard-coding a very high limit for the allowed number of open files, and this is causing some containers to fail. To resolve the problem, you should configure the Docker daemon to enforce a lower value, as described `here <https://github.com/docker-library/mysql/issues/579#issuecomment-1432576518>`__. Edit ``/etc/docker/daemon.json`` and add the following contents::
{
"default-ulimits": {
"nofile": {
"Name": "nofile",
"Hard": 1048576,
"Soft": 1048576
}
}
}
Check your configuration is valid with::
dockerd --validate
Then restart the Docker service::
sudo systemctl restart docker.service
Launch your Open edX platform again with ``tutor local launch``. You should observe normal memory usage.
"Build failed running pavelib.servers.lms: Subprocess return code: 1"
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