Restricting the number of CPUs does not work with Docker and no way of passing "--cpus" flag while the creation of an instance

[j-danek]

Hi, I am trying to setup a small number of connected containers with Docker for testing. In order to assure the same behavior on any HW, I am trying to restrict the number of CPUs for each container. And I am failing at that, while using the Docker-plugin. I have tried five ways to achieve my goal. For details see the following table and comments in the example file below.

1. passing raw argument to instance
2. setting provider options via provider_options
3. setting the argument via "cpus" in platform's details
4. setting provider options
5. passing raw arguments to provider

After the creation of the container, I would like to have
# docker inspect headnode | grep NanoCpus
"NanoCpus": 1000000000,
instead of
"NanoCpus": 0,

Is there any way how to, at least, pass raw arguments to the Docker? Or do I have to write my own Ansible script for managing Docker instances, as suggested in this example?

 - - - - OS - - - - 
PRETTY_NAME="Ubuntu 22.04.4 LTS"

- - - Molecule - - - 
molecule 24.6.0 using python 3.10 
    ansible:2.17.0
    default:24.6.0 from molecule
    docker:2.1.0 from molecule_docker requiring collections: community.docker>=3.0.2 ansible.posix>=1.4.0

molecule.yml

---
dependency:
  name: galaxy

driver:
  name: docker

platforms:
  - name: headnode
    image: docker.io/geerlingguy/docker-ubuntu2204-ansible
    command: ${MOLECULE_DOCKER_COMMAND:-""}
    pre_build_image: true
    privileged: true
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:rw
    cgroupns_mode: host
    docker_networks:  # might be used only once
      - name: molecule
        ipam_config:
          - subnet: 172.206.0.0/16
    networks:
      - name: molecule
        ipv4_address: 172.206.0.10
    instance_raw_config_args:      # 1st
      - '--cpus=1.0'               # 1st
    provider_options:              # 2nd
      cpus: "1.0"                  # 2nd
    cpus: 1                        # 3rd
    providers:                     # 4th
      - name: docker               # 4th
        type: docker               # 4th
        options:                   # 4th
          cpus: 1                  # 4th
    provider_raw_config_args:      # 5th
      - '--cpus=1.0'               # 5th

provisioner:
  name: ansible

verifier:
  name: ansible

...

[apatard]

there's atm no way to set the cpus argument of the docker_container module but I can try making a fix for that.

[j-danek]

Hi Apatard,
I see. Thank you for your answer. That fix might be useful for me and other ppl. On the other hand, there are quite some arguments, that are not considered either, like gpus .

Would it be possible to create a general argument instance_raw_config_args that would be directly attached to the command docker run executed by the plugin?

[apatard]

I've not checked the current documentation of the docker_container but I think that it doesn't have a way to specify custom arguments so no way to use instance_raw_config_args. At worse, it's always possible to copy the plugin create.yml file into your molecule scenario directory and adapt it to your needs.

[j-danek]

That is actually a good point. I had a brief look and have not find any similar parameter in the docker_container module. There is also no parameter gpus, which has to be set through the parameter device_requests.

Is it really so simple as just copying and modifying the create.yml? For now I have solved this issue by adopting the officially recommended create.yml and destroy.yml files (here)