Ansible: Run task if server belongs to a group

Question

What's the sane way run a task only if the host belongs to one or more groups?

Currently, I'm using a boolean within the relevant group, e.g.:

Inventory file

[db_servers:vars]
copy_connection_string=true

Task

-
  name: Copy db connection string file
  synchronize: src= ... (truncated for clarity)
  when: copy_connection_string is defined

What's the right condition in the when clause to check whether the current host belongs to the db_servers group?

Answer 1

Run task when a host server is a member of a specific group

Ansible contains special or magic variables - one of the most common is group_names which is a list (array) of all the groups the current host is in.

- name: Copy db connection string file
  synchronize:.........
  when: "'db_servers' in group_names"

The above Ansible task will only run if the host is a member of the db_servers group.