Ansible loop to create docker networks

Question

Suppose I have my docker networks defined in a variable such as:

docker_networks:
  - name: default
    driver: bridge
  - name: proxy
    driver: bridge
    ipam_options:
      subnet: '192.168.100.0/24'
  - name: socket_proxy
    driver: bridge
    ipam_options:
      subnet: '192.168.101.0/24'

How would I go about running this with a loop to create these docker networks?

I tried the following, however the ipam_config parameter causes it to fail if no subnet is defined:

- name: Create networks
  docker_network:
    name: '{{ item.name }}'
    driver: '{{ item.driver | default(omit) }}'
    ipam_config:
      - subnet: '{{ item.ipam_options.subnet | default(omit) }}'
  loop: '{{ docker_networks }}'

Answer 1

If you modify your docker_networks variable so that the value of the ipam_options key is a list of dictionaries:

docker_networks:
  - name: proxy
    driver: bridge
    ipam_options:
      - subnet: '192.168.100.0/24'
  - name: socket_proxy
    driver: bridge
    ipam_options:
      - subnet: '192.168.101.0/24'
  - name: no_subnet
    driver: bridge

Then you can rewrite your task like this:

- name: Create networks
  community.docker.docker_network:
    name: '{{ item.name }}'
    driver: '{{ item.driver | default(omit) }}'
    ipam_config: "{{ item.ipam_options | default(omit) }}"
  loop: '{{ docker_networks }}'

(I would also just rename the ipam_options key to ipam_config, so that it matches the parameter name.)