How to write ansible custom modules

Ansible modules are easy way to interact between an existing application and ansible playbook. This blog covers how to write your own ansible module.

Module

• Create a python file called greet.py with following content

    def main():
  
        module = AnsibleModule(
            argument_spec = dict(
                message = dict(required=True, type="str"),
            ),
            supports_check_mode=True
        )
  
        # get module params
        message = module.params.get("message")
  
        try:
            module.exit_json(changed=True, msg=message)
        except:
            module.fail_json(msg="It's bad not to greet someone")
  
    from ansible.module_utils.basic import AnsibleModule
    if __name__ == "__main__":
        main()
  

• File name greet.py is considered as ansible module.

• Arguments defined in ansible playbooks will be parsed by AnsibleModule class.

• Ansible module always returns json, for convenience ansible provides two methods, one for success and other for failure

            # For success
            module.exit_json(changed=True, msg=message)
  
            # For failure
            module.fail_json(msg="It's bad not to greet someone")
  

Usage

• Create an ansible playbook called playbook.yml

    touch playbook.yml
  

• Create directory library alongside playbook.yml and copy greet.py to library

    mkdir library
    cp greet.py library
  

• Now our directory structure should look like

    library
        |- greet.py
    playbook.yml
  

• We can now use greet module with our playbook.yml

    ---
    - hosts: localhost
      tasks:
      - name: Lets start greeting
        greet:
            message: "Good morning"
  

Done !! as simple as that ;)