Handlers

Ansible modules are designed to be idempotent. This means that in a properly written playbook, the playbook and its tasks can be run multiple times without changing the managed host unless they need to make a change to get the managed host to the desired state.

Handlers are tasks that respond to a notification triggered by other tasks.

Handlers can be considered as inactive tasks that only get triggered when explicitly invoked using a notify statement.

Example:

tasks:
  - name: Copy configuration template
    template:
      src: /var/lib/templates/example.conf.template
      dest: /etc/httpd/conf.d/example.conf
    notify:
      - restart apache

handlers:
  - name: restart apache
    service:
      name: httpd
      state: restarted

A task may call more than one handler in its notify section.

Example:

notify:
  - restart mysql
  - restart apache

• Handlers always run in the order specified by the handlers section of the play.
• Handlers normally run after all other tasks in the play complete.
• Handler names exist in a per-play namespace. If two handlers are incorrectly given the same name, only one will run.
• Even if more than one task notifies a handler, the handler only runs once.
• If a task that includes a notify statement does not report a changed result the handler is not notified.