Debugging tasks

Ansible offers a task debugger so you can try to fix errors during execution instead of fixing them in the playbook and then running it again. You have access to all of the features of the debugger in the context of the task. You can check or set the value of variables, update module arguments, and re-run the task with the new variables and arguments. The debugger lets you resolve the cause of the failure and continue with playbook execution.

Invoking the debugger

There are multiple ways to invoke the debugger.

Using the debugger keyword

New in version 2.5.

The debugger keyword can be used on any block where you provide a name attribute, such as a play, role, block or task. The debugger keyword accepts five values:

Value Result
always Always invoke the debugger, regardless of the outcome
never Never invoke the debugger, regardless of the outcome
on_failed Only invoke the debugger if a task fails
on_unreachable Only invoke the debugger if a host was unreachable
on_skipped Only invoke the debugger if the task is skipped

When you use the debugger keyword, the setting you use overrides any global configuration to enable or disable the debugger. If you define debugger at two different levels, for example in a role and in a task, the more specific definition wins: the definition on a task overrides the definition on a block, which overrides the definition on a role or play.

Here are examples of invoking the debugger with the debugger keyword:

# on a task
- name: Execute a command
  command: "false"
  debugger: on_failed

# on a play
- name: My play
  hosts: all
  debugger: on_skipped
  tasks:
    - name: Execute a command
      command: "true"
      when: False

In the example below, the task will open the debugger when it fails, because the task-level definition overrides the play-level definition:

- name: Play
  hosts: all
  debugger: never
  tasks:
    - name: Execute a command
      command: "false"
      debugger: on_failed

In configuration or an environment variable

New in version 2.5.

You can turn the task debugger on or off globally with a setting in ansible.cfg or with an environment variable. The only options are True or False. If you set the configuration option or environment variable to True, Ansible runs the debugger on failed tasks by default.

To invoke the task debugger from ansible.cfg:

[defaults]
enable_task_debugger = True

To use an an environment variable to invoke the task debugger:

ANSIBLE_ENABLE_TASK_DEBUGGER=True ansible-playbook -i hosts site.yml

When you invoke the debugger using this method, any failed task will invoke the debugger, unless it is explicitly disabled for that role, play, block, or task. If you need more granular control what conditions trigger the debugger, use the debugger keyword.

As a strategy

Note

This backwards-compatible method, which matches Ansible versions before 2.5, may be removed in a future release.

To use the debug strategy, change the strategy attribute like this:

- hosts: test
  strategy: debug
  tasks:
  ...

You can also set the strategy to debug with the environment variable ANSIBLE_STRATEGY=debug, or by modifying ansible.cfg:

[defaults]
strategy = debug

Using the debugger

Once you invoke the debugger, you can use the seven debugger commands to work through the error Ansible encountered. For example, the playbook below defines the var1 variable but uses the wrong_var variable, which is undefined, by mistake.

- hosts: test
  debugger: on_failed
  gather_facts: no
  vars:
    var1: value1
  tasks:
    - name: wrong variable
      ping: data={{ wrong_var }}

If you run this playbook, Ansible invokes the debugger when the task fails. From the debug prompt, you can change the module arguments or the variables and run the task again.

PLAY ***************************************************************************

TASK [wrong variable] **********************************************************
fatal: [192.0.2.10]: FAILED! => {"failed": true, "msg": "ERROR! 'wrong_var' is undefined"}
Debugger invoked
[192.0.2.10] TASK: wrong variable (debug)> p result._result
{'failed': True,
 'msg': 'The task includes an option with an undefined variable. The error '
        "was: 'wrong_var' is undefined\n"
        '\n'
        'The error appears to have been in '
        "'playbooks/debugger.yml': line 7, "
        'column 7, but may\n'
        'be elsewhere in the file depending on the exact syntax problem.\n'
        '\n'
        'The offending line appears to be:\n'
        '\n'
        '  tasks:\n'
        '    - name: wrong variable\n'
        '      ^ here\n'}
[192.0.2.10] TASK: wrong variable (debug)> p task.args
{u'data': u'{{ wrong_var }}'}
[192.0.2.10] TASK: wrong variable (debug)> task.args['data'] = '{{ var1 }}'
[192.0.2.10] TASK: wrong variable (debug)> p task.args
{u'data': '{{ var1 }}'}
[192.0.2.10] TASK: wrong variable (debug)> redo
ok: [192.0.2.10]

PLAY RECAP *********************************************************************
192.0.2.10               : ok=1    changed=0    unreachable=0    failed=0

As the example above shows, once the task arguments use var1 instead of wrong_var, the task runs successfully.

Available debug commands

You can use these seven commands at the debug prompt:

Command Shortcut Action
print p Print information about the task
task.args[key] = value no shortcut Update module arguments
task_vars[key] = value no shortcut Update task variables (you must update_task next)
update_task u Recreate a task with updated task variables
redo r Run the task again
continue c Continue executing, starting with the next task
quit q Quit the debugger

For more details, see the individual descriptions and examples below.

Update args command

task.args[*key*] = *value* updates a module argument. This sample playbook has an invalid package name:

- hosts: test
  strategy: debug
  gather_facts: yes
  vars:
    pkg_name: not_exist
  tasks:
    - name: install package
      apt: name={{ pkg_name }}

When you run the playbook, the invalid package name triggers an error, and Ansible invokes the debugger. You can fix the package name by viewing, then updating the module argument:

[192.0.2.10] TASK: install package (debug)> p task.args
{u'name': u'{{ pkg_name }}'}
[192.0.2.10] TASK: install package (debug)> task.args['name'] = 'bash'
[192.0.2.10] TASK: install package (debug)> p task.args
{u'name': 'bash'}
[192.0.2.10] TASK: install package (debug)> redo

After you update the module argument, use redo to run the task again with the new args.

Update vars command

task_vars[*key*] = *value* updates the task_vars. You could fix the playbook above by viewing, then updating the task variables instead of the module args:

[192.0.2.10] TASK: install package (debug)> p task_vars['pkg_name']
u'not_exist'
[192.0.2.10] TASK: install package (debug)> task_vars['pkg_name'] = 'bash'
[192.0.2.10] TASK: install package (debug)> p task_vars['pkg_name']
'bash'
[192.0.2.10] TASK: install package (debug)> update_task
[192.0.2.10] TASK: install package (debug)> redo

After you update the task variables, you must use update_task to load the new variables before using redo to run the task again.

Note

In 2.5 this was updated from vars to task_vars to avoid conflicts with the vars() python function.

Update task command

New in version 2.8.

u or update_task recreates the task from the original task data structure and templates with updated task variables. See the entry Update vars command for an example of use.

Redo command

r or redo runs the task again.

Continue command

c or continue continues executing, starting with the next task.

Quit command

q or quit quits the debugger. The playbook execution is aborted.

Debugging and the free strategy

If you use the debugger with the free strategy, Ansible does not queue or execute any further tasks while the debugger is active. However, previously queued tasks remain in the queue and run as soon as you exit the debugger. If you use redo to reschedule a task from the debugger, other queued task may execute before your rescheduled task.

See also

Executing playbooks for troubleshooting
Running playbooks while debugging or testing
Intro to Playbooks
An introduction to playbooks
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