How can I run another role inside Ansible?

There are several ways to run another role inside Ansible. The most common and recommended method is to use the roles: keyword within your playbook or within another role's main.yml file.

Here's how you can achieve this:

1. Using the `roles:` keyword in a Playbook:

This is the most straightforward approach when you want to include other roles in your main playbook. Suppose you have two roles: webserver and database. Your playbook might look like this:

---
- hosts: all
become: true
roles:
- webserver
- database


In this example, Ansible will execute the webserver role first, followed by the database role on all hosts.

2. Using the `roles:` keyword inside another Role:

You can also include a role within another role. For example, if your webserver role requires a common role for shared configurations, you can include it in the webserver/tasks/main.yml file:

---
- name: Include Common Role
roles:
- common
- name: Configure Web Server
# ... other tasks specific to the webserver role ...


In this case, the common role will be executed before any other tasks defined within the webserver role.

3. Using `include_role` and `import_role` (Less Common):

While roles: is generally preferred, you can also use include_role or import_role tasks. The main difference between them is that import_role is static (processed at playbook parsing time), while include_role is dynamic (processed at runtime).

Example using include_role:

---
- name: Include Database Role
include_role:
name: database
vars:
database_port: 5432


Example using import_role:

---
- name: Import Common Role
import_role:
name: common
vars:
common_setting: "some_value"


Key Considerations:

- Role Dependencies: Ensure that roles are designed to be independent where possible, but understand dependencies if one role relies on another for specific configurations.

- Variable Scoping: Variables defined in a role can be overridden by variables in the playbook or in another role that is executed later. Be mindful of variable precedence.

- Idempotency: Roles should be idempotent, meaning they can be run multiple times without changing the system state beyond the initial application of the configuration.

By using the roles: keyword, you can effectively structure your Ansible playbooks to execute different roles in a specific order, making your infrastructure code more modular and maintainable. Remember to organize your roles logically and handle dependencies appropriately to ensure a smooth and predictable deployment process.

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