Ansible Roles - Role Dependencies

1. Introduction

In Ansible, roles are a way to organize playbooks and manage configurations. Role dependencies allow you to build modular, reusable roles by specifying other roles that must be executed before the current role.

2. What are Role Dependencies?

Role dependencies are a mechanism to define relationships between roles in Ansible. By declaring dependencies, you ensure that certain roles are executed before others, which can be critical for setups where one role relies on the resources or configurations provided by another.

3. Defining Dependencies

Dependencies are defined in the meta/main.yml file of a role. Here’s how you can specify dependencies:

dependencies:
  - role: common
  - role: database
    vars:
      db_name: example_db

In this example:

• The role depends on a role named common.
• It also depends on another role named database, with a variable db_name defined for its execution.

4. Best Practices

When working with role dependencies, consider the following best practices:

1. Keep dependencies minimal to avoid tight coupling.
2. Document role dependencies clearly within meta/main.yml.
3. Test roles independently to ensure they function correctly without dependencies.
4. Use version constraints for dependencies to avoid breaking changes.

5. Example

Here’s a complete example of how a role might look with dependencies:

---
# meta/main.yml
dependencies:
  - role: common
  - role: database
    vars:
      db_name: example_db

# tasks/main.yml
- name: Ensure the application is installed
  apt:
    name: myapp
    state: present

6. FAQ