Ansible: Restart server only if config changed

gistfile1.txt

- name: Backup original my.cnf
  copy: remote_src=true src=/etc/mysql/my.cnf dest=/tmp/my.cnf.recent

- name : Update my.cnf
  template: src=my.cnf.j2 dest=/etc/mysql/my.cnf owner=mysql mode=0644

# diff returns error code if different, so we ignore "errors"
- name: Check if my.cnf changed
  command: diff /etc/mysql/my.cnf /tmp/my.cnf.recent
  ignore_errors: true
  register: mysql_diff

- name: Restart MySQL service if my.cnf changed
  service: name=mysql state=restarted
  when: "{{mysql_diff.rc}} > 0"