ansible/docsite/rst/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.


.. code-block:: YAML
 :emphasize-lines: 2
 :caption: Block example

    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.


.. _block_error_handling:

Error Handling
``````````````

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

.. code-block:: YAML
 :emphasize-lines: 2,6,10
 :caption: Block error handling example

  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 :

.. code-block:: YAML
 :emphasize-lines: 4,8
 :caption: Block run handlers in error handling

  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