playbooks_blocks.rst

Blocks

In 2.0 we added a block feature to allow for logical grouping of tasks and even in play error handling. Most of what you can apply to a single task can be applied at the block level, which also makes it much easier to set data or directives common to the tasks.

   tasks:
     - block:
         - yum: name={{ item }} state=installed
           with_items:
             - httpd
             - memcached

         - template: src=templates/src.j2 dest=/etc/foo.conf

         - service: name=bar state=started enabled=True

       when: ansible_distribution == 'CentOS'
       become: true
       become_user: root

In the example above, each of the 3 tasks will be executed after appending the when condition from the block and evaluating it in the task's context. Also they inherit the privilege escalation directives enabling "become to root" for all the enclosed tasks.

Error Handling

Blocks also introduce the ability to handle errors in a way similar to exceptions in most programming languages.

 tasks:
  - block:
      - debug: msg='i execute normally'
      - command: /bin/false
      - debug: msg='i never execute, cause ERROR!'
    rescue:
      - debug: msg='I caught an error'
      - command: /bin/false
      - debug: msg='I also never execute :-('
    always:
      - debug: msg="this always executes"

The tasks in the block would execute normally, if there is any error the rescue section would get executed with whatever you need to do to recover from the previous error. The always section runs no matter what previous error did or did not occur in the block and rescue sections.

Another example is how to run handlers after an error occurred :

 tasks:
  - block:
      - debug: msg='i execute normally'
        notify: run me even after an error
      - command: /bin/false
    rescue:
      - name: make sure all handlers run
        meta: flush_handlers
 handlers:
   - name: run me even after an error
     debug: msg='this handler runs even on error'

.. seealso::

   :doc:`playbooks`
       An introduction to playbooks
   :doc:`playbooks_roles`
       Playbook organization by roles
   `User Mailing List <http://groups.google.com/group/ansible-devel>`_
       Have a question?  Stop by the google group!
   `irc.freenode.net <http://irc.freenode.net>`_
       #ansible IRC chat channel