Delegating a task

Sometimes you want to execute an action on a different system. This could be, for instance, a database node while you are deploying something on an application server node or to the local host. To do so, you can just add the 'delegate_to: HOST' property to your task and it will be run on the proper node. Let's rework the previous example to achieve this:

    --- 
    - hosts: database 
      remote_user: ansible 
      tasks: 
      - name: Count processes running on the remote system 
        shell: ps | wc -l 
        register: remote_processes_number 
      - name: Print remote running processes 
        debug: 
          msg: '{{ remote_processes_number.stdout }}' 
      - name: Count processes running on the local system 
        shell: ps | wc -l 
        delegate_to: localhost 
        register: local_processes_number 
      - name: Print local running processes 
        debug: 
          msg: '{{ local_processes_number.stdout }}' 

Saving it as delegate_to.yaml, we...