A Debugger for Ansible Playbook
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README.md

ansible-playbook-debugger

This tool is merged into Ansible v2.1! If you are using v2.1 or later, see official usage documents.

ansible-playbook-debugger is the tool to debug a playbook. This debugger is invoked when the task in the playbook fails, and enables you to check useful debug info such as module's args, and variables. Also, you can change module's args in the debugger, and run the failed task again to make sure a bug is fixed.

NOTE: the debugger in v0.3.0 or later does not support ansible v1. If you use ansible v1, the debugger's version should be v0.2.4 or earlier.

For example, let's 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.

$ ansible-playbook example1.yml -i inventory

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

TASK [wrong variable] **********************************************************
fatal: [54.249.1.1]: 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: [54.249.1.1]

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

This time, the task runs successfully!

Installation

Make a strategy_plugins directory in your playbook directory, and put debug.py inside of it.

mkdir strategy_plugins
cd strategy_plugins
wget https://raw.githubusercontent.com/ks888/ansible-playbook-debugger/master/strategy_plugins/debug.py

Setup

Open your playbook, and add strategy: debug line like this:

- hosts: all
  strategy: debug
  ...

Usage

Run

Run ansible-playbook command as usual. This debugger is invoked when the task in a playbook fails, and show (debug) prompt. See Available Commands to check the debugger's commands.

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'172.31.6.88'],
 u'ansible_all_ipv6_addresses': [u'fe80::497:a8ff:fe70:d9'],
 u'ansible_architecture': u'x86_64',
 ...
}
(debug) p vars['pkg_name']
u'bash'
(debug) p host
54.249.1.1
(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.

Contributing

Contributions are very welcome. Feel free to open an issue or create a pull request.