We use the Ansible rax module to create new instances of our “cloud servers”. It’s pretty easy to add them to one group:

- name: Build a Cloud Server
  tasks:
      local_action:
        module: rax
        name: rax-test1
        wait: yes
        state: present
        networks:
          - private
          - public
        group: app-servers

But it’s also quite handy to be able to place a server in multiple groups (e.g. test / production, different regions etc). There’s nothing in the documentation about this, but a bit of code spelunking reveals that a metadata key named “groups” can contain a comma-separated list of extra host groups:

- name: Build a Cloud Server
  tasks:
      local_action:
        module: rax
        name: rax-test1
        wait: yes
        state: present
        networks:
          - private
          - public
        group: app-servers
        meta:
            groups: test, london