Custom ansible modules

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"