Ansible hostvars undefined

Question

I have a very simple play which saves vars and looks them up in hostvars.

- name: Set hostvars
  hosts: localhost
  vars:
    var_one: "I am a"
    var_two: "test"
  tasks:
    - debug: var=hostvars['localhost']['var_one']
    - debug: var=hostvars['localhost']['var_two']

However, when I run this play the vars aren't defined:

PLAY [Set hostvars] ************************************************************

TASK [setup] *******************************************************************
ok: [localhost]

TASK [debug] *******************************************************************
ok: [localhost] => {
    "hostvars['localhost']['var_one']": "VARIABLE IS NOT DEFINED!"
}

TASK [debug] *******************************************************************
ok: [localhost] => {
    "hostvars['localhost']['var_two']": "VARIABLE IS NOT DEFINED!"
}

How can I save these vars in hostvars?

Answer 1

You can set host facts runtime using set_fact module:

---
- name: Set hostvars
  hosts: localhost
  tasks:
    - set_fact: var_one="I am a"
    - set_fact: var_two="test"
    - debug: var=hostvars['localhost']['var_one']
    - debug: var=hostvars['localhost']['var_two']

Quoting the documentation:

These variables will survive between plays during an Ansible run, but will not be saved across executions even if you use a fact cache.

Answer 2

This is where the difference between facts (variables bound to Ansible target hosts) and regular variables can be seen.

Variables are internally stored in vars structure, so you can access them with:

tasks:
  - debug: var=vars['var_one']
  - debug: var=vars['var_two']

Facts, on the other hand are stored in hostvars.

---

In either case, unless you were referring to a variable name with a dynamic name, or a fact bound to another host than the one executing the task, you can simply use the variable/fact name by using its name:

tasks:
  - debug: var=var_one
  - debug: var=var_two