#!/usr/bin/env ansible-playbook
---

- name: DEPLOY BENCHMARK SERVER
  hosts: bench_server
  pre_tasks:
    - name: "Fail is benchmark server is not unique"
      fail:
        msg: "Benchmark server must be unique"
      when: groups['bench_server'] | length > 1
  tags: bench_server
  roles: 
    - bench-server

- name: DEPLOY BENCHMARK WORKERS
  hosts: bench_worker
  tags: bench_worker
  roles: 
    - bench-worker

...