Linux can report what compute resources are used by processes in a specific cgroup or Docker container. Crunch can use these reports to share that information with users running compute work. This can help workflow authors debug and optimize their workflows.
To enable cgroups accounting, you must boot Linux with the command line parameters
Currently Arvados is not compatible with the new cgroups accounting, also known as cgroups v2. Currently, all supported GNU/Linux distributions don’t use cgroups v2 as default
If you are using a distribution in the compute nodes that ships with cgroups v2 enabled, make sure to disable it by booting Linux with the command line parameters
After making changes, reboot the system to make these changes effective.
~$ sudo grubby --update-kernel=ALL --args='cgroup_enable=memory swapaccount=1 systemd.unified_cgroup_hierarchy=0'
Open the file
/etc/default/grub in an editor. Find where the string
GRUB_CMDLINE_LINUX is set. Add
cgroup_enable=memory swapaccount=1 systemd.unified_cgroup_hierarchy=0 to that string. Save the file and exit the editor. Then run:
~$ sudo update-grub
Compute nodes must have Docker installed to run containers. This requires a relatively recent version of Linux (at least upstream version 3.10, or a distribution version with the appropriate patches backported). Follow the Docker Engine installation documentation for your distribution.
Make sure Docker is enabled to start on boot:
# systemctl enable --now docker
Depending on your anticipated workload or cluster configuration, you may need to tweak Docker options.
For information about how to set configuration options for the Docker daemon, see https://docs.docker.com/config/daemon/systemd/
Docker containers inherit ulimits from the Docker daemon. However, the ulimits for a single Unix daemon may not accommodate a long-running Crunch job. You may want to increase default limits for compute containers by passing
--default-ulimit options to the Docker daemon. For example, to allow containers to open 10,000 files, set
ValidationException: Not found: '/var/lib/cwl/workflow.json#main'
A possible configuration error is having Docker installed as a
snap package rather than a
deb package. This is a problem because
snap packages are partially containerized and may have a different view of the filesystem than
crunch-run. This will produce confusing problems, for example, directory bind mounts sent to Docker that are empty (instead of containing the intended files) and resulting in unexpected “file not found” errors.
To check for this situation, run
snap list and look for
docker. If found, run
snap remove docker and follow the instructions to above to install Docker Engine .
The content of this documentation is licensed under the
Commons Attribution-Share Alike 3.0 United States licence.
Code samples in this documentation are licensed under the Apache License, Version 2.0.