- hosts: collectd
  roles:
  - role: collectd
    tags:
    - collectd

- hosts: prometheus
  roles:
  - role: collectd-prometheus
    tags:
    - collectd
    - collectd-prometheus

- hosts: collectd
  tasks:
  - name: ensure collectd is running
    service:
      name: collectd
      state: started
    tags:
    - service