Ansible: print warnings from playbook

Question

Can I print a warning from Ansible as Ansible does for internal warning like:

 [WARNING]: Ignoring invalid attribute: xx

The targetted use are warning, that are not error, so they should not end the playbook execution, butthey should be clearly visible (in standard Ansible purple color).

Example usage:

1. I have some hardcoded URL of the latest release.
2. The playbook downloads the latest avaiable URL.
3. And print warning if the URLs differs.
4. As the source is not trusted, the downloaded URL is should be used only for comparison, but not used directly.

Answer 1

Warnings can be sort of kludged by using fail: + when: + ignore_errors:.

e.g.

- name: Check hostname matches entry in ansible/hosts
  fail:
    msg: "Warning: Expected hostname to be '{{ inventory_hostname }}' but was '{{ ansible_facts.fqdn}}'"
  when: ansible_facts.fqdn != inventory_hostname
  ignore_errors: True

The warnings show up as fatal errors, followed by ...skipping, and a count of the number them will appear in the PLAY RECAP as ignored=N.

e.g.

TASK [mytask: Check hostname matches entry in ansible/hosts] ***************
fatal: [myhost]: FAILED! => {"changed": false, "msg": "Warning: Expected hostname to be 'myhost' but was 'myhost.my.example.com'"}
...ignoring

PLAY RECAP *************************************************************************************
myhost   ok=0    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    **ignored=1**

credit: https://medium.com/opsops/how-to-print-warning-from-a-task-3286ebb39f40

Answer 2

Here is a simple filter plugin that will emit a Warning message:

from ansible.utils.display import Display


class FilterModule(object):
    def filters(self): return {'warn_me': self.warn_filter}

    def warn_filter(self, message, **kwargs):
        Display().warning(message)
        return message

Place the above into a file in, for example, [playbook_dir]/filter_plugins/warn_me.py.

A contrived example playbook that calls this filter might look like this:

---
- name: Demonstrate warn_me filter plugin
  gather_facts: no
  hosts: all

  tasks:
    - meta: end_play 
      when: ('file XYZ cannot be processed' | warn_me())
      delegate_to: localhost
      run_once: yes

And running this playbook might produce this output:

$ ansible-playbook test_warnme.yml -l forwards
 __________________________________________ 
< PLAY [Demonstrate warn_me filter plugin] >
 ------------------------------------------ 
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

 [WARNING]: file XYZ cannot be processed

 ____________ 
< PLAY RECAP >
 ------------ 
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||