Robin Schneider d76dd56ca3

Use addresses and names reserved for documentation

Trying to preserve the meaning of the examples. Not all occurrences in
`docsite/rst/playbooks_lookups.rst` have been changed for instance to
allow the unchanged examples to be used for testing.

Related to: #17479

2016-09-11 17:31:41 +02:00

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Playbook Debugger

Topics

In 2.1 we added a debug strategy. This strategy enables you to invoke a debugger when a task is failed, and check several info, such as the value of a variable. Also, it is possible to update module arguments in the debugger, and run the failed task again with new arguments to consider how you can fix an issue.

To use debug strategy, change strategy attribute like this:

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

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 wrong_var variable is undefined. Let's change the module's args, 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.

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