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Error Handling In Playbooks
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===========================
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.. contents:: Topics
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Ansible normally has defaults that make sure to check the return codes of commands and modules and
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it fails fast -- forcing an error to be dealt with unless you decide otherwise.
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Sometimes a command that returns 0 isn't an error. Sometimes a command might not always
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need to report that it 'changed' the remote system. This section describes how to change
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the default behavior of Ansible for certain tasks so output and error handling behavior is
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as desired.
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.. _ignoring_failed_commands:
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Ignoring Failed Commands
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````````````````````````
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.. versionadded:: 0.6
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Generally playbooks will stop executing any more steps on a host that
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has a failure. Sometimes, though, you want to continue on. To do so,
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write a task that looks like this::
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- name: this will not be counted as a failure
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command: /bin/false
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ignore_errors: yes
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Note that the above system only governs the failure of the particular task, so if you have an undefined
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variable used, it will still raise an error that users will need to address.
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.. _handlers_and_failure:
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Handlers and Failure
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````````````````````
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.. versionadded:: 1.9.1
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When a task fails on a host, handlers which were previously notified
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will *not* be run on that host. This can lead to cases where an unrelated failure
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can leave a host in an unexpected state. For example, a task could update
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a configuration file and notify a handler to restart some service. If a
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task later on in the same play fails, the service will not be restarted despite
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the configuration change.
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You can change this behavior with the ``--force-handlers`` command-line option,
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or by including ``force_handlers: True`` in a play, or ``force_handlers = True``
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in ansible.cfg. When handlers are forced, they will run when notified even
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if a task fails on that host. (Note that certain errors could still prevent
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the handler from running, such as a host becoming unreachable.)
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.. _controlling_what_defines_failure:
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Controlling What Defines Failure
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````````````````````````````````
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.. versionadded:: 1.4
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Suppose the error code of a command is meaningless and to tell if there
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is a failure what really matters is the output of the command, for instance
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if the string "FAILED" is in the output.
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Ansible in 1.4 and later provides a way to specify this behavior as follows::
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- name: this command prints FAILED when it fails
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command: /usr/bin/example-command -x -y -z
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register: command_result
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failed_when: "'FAILED' in command_result.stderr"
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In previous version of Ansible, this can be still be accomplished as follows::
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- name: this command prints FAILED when it fails
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command: /usr/bin/example-command -x -y -z
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register: command_result
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ignore_errors: True
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- name: fail the play if the previous command did not succeed
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fail: msg="the command failed"
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when: "'FAILED' in command_result.stderr"
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.. _override_the_changed_result:
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Overriding The Changed Result
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`````````````````````````````
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.. versionadded:: 1.3
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When a shell/command or other module runs it will typically report
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"changed" status based on whether it thinks it affected machine state.
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Sometimes you will know, based on the return code
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or output that it did not make any changes, and wish to override
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the "changed" result such that it does not appear in report output or
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does not cause handlers to fire::
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tasks:
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- shell: /usr/bin/billybass --mode="take me to the river"
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register: bass_result
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changed_when: "bass_result.rc != 2"
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# this will never report 'changed' status
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- shell: wall 'beep'
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changed_when: False
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Aborting the play
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`````````````````
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Sometimes it's desirable to abort the entire play on failure, not just skip remaining tasks for a host.
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The ``any_errors_fatal`` play option will mark all hosts as failed if any fails, causing an immediate abort::
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- hosts: somehosts
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any_errors_fatal: true
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roles:
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- myrole
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for finer-grained control ``max_fail_percentage`` can be used to abort the run after a given percentage of hosts has failed.
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.. seealso::
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:doc:`playbooks`
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An introduction to playbooks
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:doc:`playbooks_best_practices`
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Best practices in playbooks
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:doc:`playbooks_conditionals`
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Conditional statements in playbooks
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:doc:`playbooks_variables`
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All about variables
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`User Mailing List <http://groups.google.com/group/ansible-devel>`_
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Have a question? Stop by the google group!
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`irc.freenode.net <http://irc.freenode.net>`_
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#ansible IRC chat channel
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