Access variable from one role in another role in an Ansible playbook with multiple hosts

Question

I'm using the latest version of Ansible, and I am trying to use a default variable in role-one used on host one, in role-two, used on host two, but I can't get it to work.

Nothing I have found in the documentation or on StackOverflow has really helped. I'm not sure what I am doing wrong. Ideally I want to set the value of the variable once, and be able to use it in another role for any host in my playbook.

I've broken it down below.

In my inventory I have a hosts group called [test] which has two hosts aliased as one and two.

[test]
one ansible_host=10.0.1.10 ansible_connection=ssh ansible_user=centos ansible_ssh_private_key_file=<path_to_key>
two ansible_host=10.0.1.20 ansible_connection=ssh ansible_user=centos ansible_ssh_private_key_file=<path_to_key>

I have a single playbook with a play for each of these hosts and I supply the hosts: value as "{{ host_group }}[0]" for host one and "{{ host_group }}[1]" for host two.

The play for host one uses a role called role-one and the play for host two uses a role called role-two.

- name: Test Sharing Role Variables
  hosts: "{{ host_group }}[0]"
  roles:
    - ../../ansible-roles/role-one

- name: Test Sharing Role Variables
  hosts: "{{ host_group }}[1]"
  roles:
    - ../../ansible-roles/role-two

In role-one I have set a variable variable-one.

---
# defaults file for role-one

variable_one: Role One Variable

I want to use the value of variable_one in a template in role-two but I haven't had any luck. I'm using the below as a task in role-two to test and see if the variable is getting "picked-up".

---
# tasks file for role-two
- debug:
    msg: "{{ variable_one }}"

When I run the playbook with ansible-playbook test.yml --extra-vars "host_group=test" I get the below failure.

TASK [../../ansible-roles/role-two : debug] ***********************************************************************************************************************************************************************************************
fatal: [two]: FAILED! => {"msg": "The task includes an option with an undefined variable. The error was: \"hostvars['test']\" is undefined\n\nThe error appears to be in 'ansible-roles/role-two/tasks/main.yml': line 3, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n# tasks file for role-two\n- debug:\n  ^ here\n"}

larsks larsks · Accepted Answer · 2020-12-16T12:57:31

Variables declared in roles are scoped to the play. If you want to access a variable from role-one in role-two, they would both need to be in the same play. For example, you could write:

- name: Test Sharing Role Variables
  hosts: "{{ host_group }}"
  tasks:
    - import_role:
        name: role-one
      when: inventory_hostname == "one"

    - import_role:
        name: role-two
      when: inventory_hostname == "two"

Alternatively, you could restructure your roles so that the variables can be imported separately from your actions. That is, have a role_one_vars role that does nothing but define variables, and then you can import that in both role-one and role-two. That is, you would have a structure something like:

playbook.yml
hosts
roles/
  role-one/
    tasks/
      main.yml
  role-one-vars/
    variables/
      main.yml
  role-two/
    tasks/
      main.yml

And role-one/tasks/main.yml would look like:

- import_role:
    name: role-one-vars

- debug:
    msg: "in role-one: {{ variable_one }}"

role-two/tasks/main.yml would look like:

---
- import_role:
    name: role-one-vars

- debug:
    msg: "in role-two: {{ variable_one }}"

And role-one-vars/vars/main.yml would look like:

---
variable_one: role one variable

Putting this all together, the output looks like:


PLAY [Test Sharing Role Variables] *****************************************************************************************************************************************

TASK [Gathering Facts] *****************************************************************************************************************************************************
ok: [one]

TASK [role-one : debug] ****************************************************************************************************************************************************
ok: [one] => {
    "msg": "in role-one: role one variable"
}

PLAY [Test Sharing Role Variables] *****************************************************************************************************************************************

TASK [Gathering Facts] *****************************************************************************************************************************************************
ok: [two]

TASK [role-two : debug] ****************************************************************************************************************************************************
ok: [two] => {
    "msg": "in role-two: role one variable"
}

PLAY RECAP *****************************************************************************************************************************************************************
one                        : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
two                        : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Access variable from one role in another role in an Ansible playbook with multiple hosts

2 Answers