Blocks — Ansible Documentation

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# 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. This does not mean the directive affects the block itself, but is inherited by the tasks enclosed by a block. i.e. a when will be applied to the tasks, not the block itself.

Block example

       tasks:
         - name: Install Apache
           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.

New in version 2.3: The `name:` keyword for `blocks:` was added in Ansible 2.3.

## Error Handling

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

Block error handling example

      tasks:
       - name: Attempt and gracefull roll back demo
         block:
           - debug: msg='I execute normally'
           - command: /bin/false
           - debug: msg='I never execute, due to the above task failing'
         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 :

Block run handlers in error handling

     tasks:
       - name: Attempt and gracefull roll back demo
         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'

See also

Playbooks
  An introduction to playbooks
Roles
  Playbook organization by roles
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irc.freenode.net
  #ansible IRC chat channel