system-config/playbooks/zuul_rolling_restart.yaml

# Run this with "-f 20"

- hosts: 'zuul-merger:!disabled'
  tasks:
    - include_role:
        name: zuul-merger
        tasks_from: graceful

- hosts: 'zuul-executor:!disabled'
  serial: 6
  tasks:
    - include_role:
        name: zuul-executor
        tasks_from: graceful
    - include_role:
        name: zuul-executor
        tasks_from: start

- hosts: 'zuul-merger:!disabled'
  tasks:
    - include_role:
        name: zuul-merger
        tasks_from: start