Parametrized notification - question about the concept

[Tomáš Kadlec]

Hi,

I am playing around with parametrized notifications (handler calls) and I have came to the following questions:

1/ Is it documented somewhere? I did not find anything about the subject in official docs only several issues on github (e.g. https://github.com/ansible/ansible/issues/4853#issuecomment-28719258). So please forgive me that I am only guessing.

2/ I have not found any valid reason to parametrize a notification with role variable only. Is there any? I am confused by this kind of behavior.

To be clear I am trying to notify a handler named client-handler-something and that something is stored as a variable. The task that notifies an appropriate handler may look as follows.

---
# roles/client/tasks/main.yml

- name: "notify client-handler"
  debug:
    msg: "Handler: {{handler_name}}"
  changed_when: true
  notify:
    - "{{handler_name}}"


- name: "run client-handler immediately"
  meta: flush_handlers

If I pass the variable with the role, it works.

---
# playbook.yml
- roles:
  - { role: client, handler_name: something }

If I use set_fact or try to compute the value on the fly it does not.

---
# roles/client/tasks/main.yml

- set_fact:
    handler_name: "client-handler-{{client.type|default('none')}}"

- name: "notify client-handler"
  debug:
    msg: "Handler: {{handler_name}}"
  changed_when: true
  notify:
    - "{{handler_name}}"

I would like to know why. I assume that this is a general concept which can be very useful and it does not have nothing to do with roles in my opinion.

Thanks for clarifying this for me.

Tomas