ansible/docs/docsite/rst/playbooks_debugger.rst

Playbook Debugger

Topics

Ansible includes a debug strategy. This strategy enables you to invoke a debugger when a task has failed. You have access to all of the features of the debugger in the context of the failed task. You can then, for example, check or set the value of variables, update module arguments, and re-run the failed task with the new variables and arguments to help resolve the cause of the failure.

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

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

If you don't want change the code, you can define ANSIBLE_STRATEGY=debug environment variable in order to enable the debugger.

For example, run the playbook below:

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

The debugger is invoked since the wrong_var variable is undefined.

Let's change the module's arguments 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
(debug) p result
{'msg': u"ERROR! 'wrong_var' is undefined", 'failed': True}
(debug) p task.args
{u'data': u'{{ wrong_var }}'}
(debug) task.args['data'] = '{{ var1 }}'
(debug) p task.args
{u'data': '{{ var1 }}'}
(debug) redo
ok: [192.0.2.10]

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

This time, the task runs successfully!

Available Commands

p task/vars/host/result

Print values used to execute a module:

(debug) p task
TASK: install package
(debug) p task.args
{u'name': u'{{ pkg_name }}'}
(debug) p vars
{u'ansible_all_ipv4_addresses': [u'192.0.2.10'],
 u'ansible_architecture': u'x86_64',
 ...
}
(debug) p vars['pkg_name']
u'bash'
(debug) p host
192.0.2.10
(debug) p result
{'_ansible_no_log': False,
 'changed': False,
 u'failed': True,
 ...
 u'msg': u"No package matching 'not_exist' is available"}

task.args[key] = value

Update module's argument.

If you run a playbook like this:

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

Debugger is invoked due to wrong package name, so let's fix the module's args:

(debug) p task.args
{u'name': u'{{ pkg_name }}'}
(debug) task.args['name'] = 'bash'
(debug) p task.args
{u'name': 'bash'}
(debug) redo

Then the task runs again with new args.

vars[key] = value

Update vars.

Let's use the same playbook above, but fix vars instead of args:

(debug) p vars['pkg_name']
u'not_exist'
(debug) vars['pkg_name'] = 'bash'
(debug) p vars['pkg_name']
'bash'
(debug) redo

Then the task runs again with new vars.

r(edo)

Run the task again.

c(ontinue)

Just continue.

q(uit)

Quit from the debugger. The playbook execution is aborted.

playbooks

An introduction to playbooks

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