Ansible playbook: load internal inventory file while running

Question

I hava an inventory file in INI format:

for example:

[db]
8.8.8.8 ansible_user=root ansible_ssh_private_key_file=/keys/root-id_rsa.pem
....

I'm looking for a way to automatically load my inventory file while running without specify which inventory file path when I triggered my ansible-playbook command

ansible-playbook playbook.yml --inventory-file=hosts (I'm trying to avoid from this) -vv

I'm familiar with the "add_host" module but still I prefer to create an inventory file in INI format and somehow to let the playbook load it automatically. is that possible?

Edit:

Thanks to the users @techraf and @Jeff Hemmen I added more details to question

In addition, I don't want to use either the ansible.cfg file because I want to perform this inside the playbook.yml file itself and not from outside

something like:

- name: add_host {{environment_type}} db servers
  hosts: localhost
  vars_files:
     - vars/main.yml
  roles:
       - { role: my_role}
  inventory_file: (possible?)
     - inventory/hosts.ini (possible?)

Answer 1

I want to perform this inside the playbook.yml file itself and not from outside

You cannot set an inventory file inside the playbook. Playbook is a list of plays and plays must have hosts declaration. There is no way to refer from inside the playbook to the inventory before Ansible tries (and fails to) interpret hosts.

Specify inventory in the ansible.cfg file stored in the same directory as your playbook:

[defaults]
inventory = ./hosts