Ref : Ansible Roles

Ansible Role Hierarchy Explained

Ansible supports property hierarchy, the ansible variable can be overwritten if the following condition mataches

Ansible Order of Execution is

• If roles/roletest/tasks/main.yml exists, tasks listed therein will be added to the play
• If roles/roletest/handlers/main.yml exists, handlers listed therein will be added to the play
• If roles/roletest/vars/main.yml exists, variables listed therein will be added to the play
• If roles/roletest/defaults/main.yml exists, variables listed therein will be added to the play
• If roles/roletest/meta/main.yml exists, any role dependencies listed therein will be added to the list of roles

Lets Begin the Test

first create the directory structure used in this example

mkdir -p roles/roletest/tasks/
mkdir -p roles/roletest/vars/
mkdir -p roles/roletest/handlers/
mkdir -p roles/roletest/defaults/
mkdir -p group_vars/

To begin this test, first we define an ansible variable first in the roletest/defaults/main.yml and in the **roletest/vars/main.yml **

[ansible@controller roles]$ cat roletest/defaults/main.yml 
first: coming default main
[ansible@controller roles]$ cat roletest/vars/main.yml 
first: 'coming from vars main'
[ansible@controller roles]$ 

The tasks/main.yml file, a very basic definition with debugging tasks the ansible variable first from where it's picking

[ansible@controller roles]$ cat roletest/tasks/main.yml 
---
  - debug:
      msg: "{{first}}"

The sample roletest test Playbook run file

[ansible@controller opt]$ cat roletest.yml 
- hosts: localhost
  roles:
     - { role: roletest }

Running the playbook, In the first example the first variable is loaded from the roletest/vars/main.yml file, since the tasks/main.yml doesn't contain any first variable

[ansible@controller opt]$ ansible-playbook roletest.yml 
TASK [roletest : debug] *****************************************************************************************
ok: [localhost] => {
    "msg": "coming from vars main"
}

Now remove this variable first from the roletest/vars/main.yml file and re-run the playbook

This time variable is picked from roletest/defualt/main.yml

TASK [roletest : debug] *****************************************************************************************
ok: [localhost] => {
    "msg": "coming default main"
}

Overriding Property

create variable first in the **group_vars/all.yml ** and re-run the Playbook (Group Variable)

[ansible@controller opt]$ cat group_vars/all.yml 
first: "Inside groupvar"

On the Playbook run this property is overridden by group variable

TASK [roletest : debug] *****************************************************************************************
ok: [localhost] => {
    "msg": "coming from groupvar"
}

Placing This property in the Inventory Hosts (Host Variables)

[local]
localhost first="Coming from Inventroy"

Run the Ansible Playbook you will be notice inventory property is given with max priority from group variable

TASK [roletest : debug] *****************************************************************************************
ok: [localhost] => {
    "msg": "Coming from the Inventory"
}

overriding all property

In this example we will be passing the first variable in the Ansible main playbook run file roletest.yml

[ansible@controller opt]$ cat roletest.yml 
- hosts: localhost
  vars:
     - first: "Coming from Main run"
  roles:
     - { role: roletest }

After running the Playbook, this ansible variable first has picked up the Max priority

TASK [roletest : debug] *****************************************************************************************
ok: [localhost] => {
    "msg": "Coming from Main run"
}

At the begining we have told variable placed in tasks/main.yml will have the MAX preferences, Now this ansible variable first is defined as HOST_VARIABLE , GROUP_VARS, defaults and vars

Modifying the file tasks/main.yml and including the variable file myvar.yml

[ansible@controller opt]$ cat roles/roletest/tasks/main.yml 
---
  - include_vars: myvar.yml
  - debug:
      msg: "{{first}}"

Place this file myvar.yml under roletest/vars/ and run the playbook

The sample Content of the file

[ansible@controller opt]$ cat roles/roletest/vars/myvar.yml 
first: 'THIS ALWAYS GIVE FIRST PRIORITY'

TASK [roletest : debug] *****************************************************************************************
ok: [localhost] => {
    "msg": "THIS ALWAYS GIVE FIRST PRIORITY"
}

Thanks for reading, Consider Paypal