site.yml

---
# This is a single playbook.

- name: all servers
  hosts: all
  sudo: true

  roles:
    - { role: foo, tags: [common, foo] }
    - { role: bar, tags: [common ,bar] }
    - { role: baz, tags: [common, baz] }

- name: database servers
  hosts: database
  sudo: true

  roles:
    - { role: postgres, tags: [database, postgres] }

- name: cache servers
  hosts: cache
  sudo: true

  roles:
    - { role: redis, tags: [cache, redis] }