Re-using Ansible artifacts

You can write a simple playbook in one very large file, and most users learn the one-file approach first. However, breaking tasks up into different files is an excellent way to organize complex sets of tasks and reuse them. Smaller, more distributed artifacts let you re-use the same variables, tasks, and plays in multiple playbooks to address different use cases. You can use distributed artifacts across multiple parent playbooks or even multiple times within one playbook. For example, you might want to update your customer database as part of several different playbooks. If you put all the tasks related to updating your database in a tasks file, you can re-use them in many playbooks while only maintaining them in one place.

• Creating re-usable files and roles
• Re-using playbooks

• Re-using files and roles

  • Includes: dynamic re-use
  • Imports: static re-use
  • Comparing includes and imports: dynamic and static re-use

• Re-using tasks as handlers

  • Triggering included (dynamic) handlers
  • Triggering imported (static) handlers

Creating re-usable files and roles

Ansible offers four distributed, re-usable artifacts: variables files, task files, playbooks, and roles.

• A variables file contains only variables.
• A task file contains only tasks.
• A playbook contains at least one play, and may contain variables, tasks, and other content. You can re-use tightly focused playbooks, but you can only re-use them statically, not dynamically.
• A role contains a set of related tasks, variables, defaults, handlers, and even modules or other plugins in a defined file-tree. Unlike variables files, task files, or playbooks, roles can be easily uploaded and shared via Ansible Galaxy. See Roles for details about creating and using roles.

Re-using playbooks

You can incorporate multiple playbooks into a main playbook. However, you can only use imports to re-use playbooks. For example:

- import_playbook: webservers.yml
- import_playbook: databases.yml

Importing incorporates playbooks in other playbooks statically. Ansible runs the plays and tasks in each imported playbook in the order they are listed, just as if they had been defined directly in the main playbook.

Re-using files and roles

Ansible offers two ways to re-use files and roles in a playbook: dynamic and static.

• For dynamic re-use, add an include_* task in the tasks section of a play:

  • include_role
  • include_tasks
  • include_vars

• For static re-use, add an import_* task in the tasks section of a play:

  • import_role
  • import_tasks

Task include and import statements can be used at arbitrary depth.

You can still use the bare roles keyword at the play level to incorporate a role in a playbook statically. However, the bare include keyword, once used for both task files and playbook-level includes, is now deprecated.

Includes: dynamic re-use

Including roles, tasks, or variables adds them to a playbook dynamically. Ansible processes included files and roles as they come up in a playbook, so included tasks can be affected by the results of earlier tasks within the top-level playbook. Included roles and tasks are similar to handlers - they may or may not run, depending on the results of other tasks in the top-level playbook.

The primary advantage of using include_* statements is looping. When a loop is used with an include, the included tasks or role will be executed once for each item in the loop.

You can pass variables into includes. See Variable precedence: Where should I put a variable? for more details on variable inheritance and precedence.

Imports: static re-use

Importing roles, tasks, or playbooks adds them to a playbook statically. Ansible pre-processes imported files and roles before it runs any tasks in a playbook, so imported content is never affected by other tasks within the top-level playbook.

You can pass variables to imports. You must pass variables if you want to run an imported file more than once in a playbook. For example:

tasks:
- import_tasks: wordpress.yml
  vars:
    wp_user: timmy

- import_tasks: wordpress.yml
  vars:
    wp_user: alice

- import_tasks: wordpress.yml
  vars:
    wp_user: bob

See Variable precedence: Where should I put a variable? for more details on variable inheritance and precedence.

Comparing includes and imports: dynamic and static re-use

Each approach to re-using distributed Ansible artifacts has advantages and limitations. You may choose dynamic re-use for some playbooks and static re-use for others. Although you can use both dynamic and static re-use in a single playbook, it is best to select one approach per playbook. Mixing static and dynamic re-use can introduce difficult-to-diagnose bugs into your playbooks. This table summarizes the main differences so you can choose the best approach for each playbook you create.

	Include_*	Import_*
Type of re-use	Dynamic	Static
When processed	At runtime, when encountered	Pre-processed during playbook parsing
Task or play	All includes are tasks	import_playbook cannot be a task
Task options	Apply only to include task itself	Apply to all child tasks in import
Calling from loops	Executed once for each loop item	Cannot be used in a loop
Using --list-tags	Tags within includes not listed	All tags appear with --list-tags
Using --list-tasks	Tasks within includes not listed	All tasks appear with --list-tasks
Notifying handlers	Cannot trigger handlers within includes	Can trigger individual imported handlers
Using --start-at-task	Cannot start at tasks within includes	Can start at imported tasks
Using inventory variables	Can include_*: {{ inventory_var }}	Cannot import_*: {{ inventory_var }}
With playbooks	No include_playbook	Can import full playbooks
With variables files	Can include variables files	Use vars_files: to import variables

Re-using tasks as handlers

You can also use includes and imports in the Handlers: running operations on change section of a playbook. For instance, if you want to define how to restart Apache, you only have to do that once for all of your playbooks. You might make a restarts.yml file that looks like:

# restarts.yml
- name: Restart apache
  ansible.builtin.service:
    name: apache
    state: restarted

- name: Restart mysql
  ansible.builtin.service:
    name: mysql
    state: restarted

You can trigger handlers from either an import or an include, but the procedure is different for each method of re-use. If you include the file, you must notify the include itself, which triggers all the tasks in restarts.yml. If you import the file, you must notify the individual task(s) within restarts.yml. You can mix direct tasks and handlers with included or imported tasks and handlers.

Triggering included (dynamic) handlers

Includes are executed at run-time, so the name of the include exists during play execution, but the included tasks do not exist until the include itself is triggered. To use the Restart apache task with dynamic re-use, refer to the name of the include itself. This approach triggers all tasks in the included file as handlers. For example, with the task file shown above:

- name: Trigger an included (dynamic) handler
  hosts: localhost
  handlers:
    - name: Restart services
      include_tasks: restarts.yml
  tasks:
    - command: "true"
      notify: Restart services

Triggering imported (static) handlers

Imports are processed before the play begins, so the name of the import no longer exists during play execution, but the names of the individual imported tasks do exist. To use the Restart apache task with static re-use, refer to the name of each task or tasks within the imported file. For example, with the task file shown above:

- name: Trigger an imported (static) handler
  hosts: localhost
  handlers:
    - name: Restart services
      import_tasks: restarts.yml
  tasks:
    - command: "true"
      notify: Restart apache
    - command: "true"
      notify: Restart mysql