Using Roles In Playbooks

Introduction to Roles

In Ansible, roles are a way to organize playbooks and tasks. Roles allow you to break down a playbook into reusable components, making it easier to manage and maintain. Each role is a collection of tasks, variables, files, templates, and modules that can be used to perform a specific function.

Creating a Role

To create a role, you can use the ansible-galaxy command. This command will generate the necessary directory structure for your role.

Command:

ansible-galaxy init my_role

This will create a directory named my_role with the following structure:

my_role/
├── defaults
│   └── main.yml
├── files
├── handlers
│   └── main.yml
├── meta
│   └── main.yml
├── tasks
│   └── main.yml
├── templates
├── tests
│   ├── inventory
│   └── test.yml
└── vars
    └── main.yml

Once you have created a role, you can use it in your playbooks. To include a role in a playbook, use the roles keyword.

Example Playbook:

---
- hosts: webservers
  roles:
    - my_role

In this example, the my_role role will be applied to all hosts in the webservers group.

Defining Tasks in a Role

Tasks are defined in the tasks/main.yml file within the role directory. Here, you can specify the tasks that should be executed as part of the role.

Example tasks/main.yml:

---
- name: Ensure Apache is installed
  apt:
    name: apache2
    state: present

- name: Start Apache service
  service:
    name: apache2
    state: started

In this example, the role will ensure that Apache is installed and started on the target hosts.

Using Variables in Roles

Variables can be defined in the vars/main.yml or defaults/main.yml file within the role directory. Variables in defaults/main.yml have the lowest precedence, while variables in vars/main.yml have a higher precedence.

Example defaults/main.yml:

---
apache_port: 80

Example tasks/main.yml using variables:

---
- name: Ensure Apache is installed
  apt:
    name: apache2
    state: present

- name: Start Apache service
  service:
    name: apache2
    state: started

- name: Ensure Apache is listening on the correct port
  lineinfile:
    path: /etc/apache2/ports.conf
    regexp: '^Listen'
    line: "Listen {{ apache_port }}"

Using Handlers in Roles

Handlers are used to perform actions when a task reports a change. Handlers are defined in the handlers/main.yml file within the role directory.

Example handlers/main.yml:

---
- name: Restart Apache
  service:
    name: apache2
    state: restarted

You can notify handlers from tasks using the notify keyword.

Example tasks/main.yml with notifications:

---
- name: Ensure Apache is installed
  apt:
    name: apache2
    state: present
  notify:
    - Restart Apache

Templates in Roles

Templates are used to generate configuration files from Jinja2 templates. Templates are stored in the templates directory within the role directory.

Example template apache2.conf.j2:

Listen {{ apache_port }}

    DocumentRoot /var/www/html

You can use the template module in your tasks to deploy these templates.

Example tasks/main.yml using a template:

---
- name: Deploy Apache configuration
  template:
    src: apache2.conf.j2
    dest: /etc/apache2/apache2.conf
  notify:
    - Restart Apache

Conclusion

In this tutorial, we've covered the basics of using roles in Ansible playbooks. Roles help you organize your playbooks into reusable components, making them easier to manage and maintain. By using roles, you can define tasks, variables, handlers, and templates in a structured way, leading to more modular and maintainable Ansible code.

Using Roles in Playbooks - Ansible Tutorial

Introduction to Roles

Creating a Role