Blocks allow for logical grouping of tasks and in play error handling. Most of what you can apply to a single task (with the exception of loops) 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.
tasks: - name: Install, configure, and start Apache block: - name: install httpd and memcached yum: name: - httpd - memcached state: present - name: apply the foo config template template: src: templates/src.j2 dest: /etc/foo.conf - name: start service bar and enable it service: name: bar state: started enabled: True when: ansible_facts['distribution'] == 'CentOS' become: true become_user: root ignore_errors: yes
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. Finally,
ignore_errors: yes will continue executing the playbook even if some of the tasks fail.
Names for tasks within blocks have been available since Ansible 2.3. We recommend using names in all tasks, within blocks or elsewhere, for better visibility into the tasks being executed when you run the playbook.
Blocks also introduce the ability to handle errors in a way similar to exceptions in most programming languages. Blocks only deal with ‘failed’ status of a task. A bad task definition or an unreachable host are not ‘rescuable’ errors.
tasks: - name: Handle the error block: - debug: msg: 'I execute normally' - name: i force a failure command: /bin/false - debug: msg: 'I never execute, due to the above task failing, :-(' rescue: - debug: msg: 'I caught an error, can do stuff here to fix it, :-)'
This will ‘revert’ the failed status of the task for the run and the play will continue as if it had succeeded.
There is also an
always section, that will run no matter what the task status is.
- name: Always do X block: - debug: msg: 'I execute normally' - name: i force a failure command: /bin/false - debug: msg: 'I never execute :-(' always: - debug: msg: "This always executes, :-)"
They can be added all together to do complex error handling.
- name: Attempt and graceful roll back demo block: - debug: msg: 'I execute normally' - name: i force a failure command: /bin/false - debug: msg: 'I never execute, due to the above task failing, :-(' rescue: - debug: msg: 'I caught an error' - name: i force a failure in middle of recovery! >:-) 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
rescue sections. It should be noted that the play continues if a
rescue section completes successfully as it ‘erases’ the error status (but not the reporting), this means it won’t trigger
any_errors_fatal configurations but will appear in the playbook statistics.
Another example is how to run handlers after an error occurred :
tasks: - name: Attempt and graceful roll back demo block: - debug: msg: 'I execute normally' changed_when: yes 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'
New in version 2.1.
Ansible also provides a couple of variables for tasks in the
rescue portion of a block:
© 2012–2018 Michael DeHaan
© 2018–2019 Red Hat, Inc.
Licensed under the GNU General Public License version 3.