As of Ansible 2.0 there seems to be an option called strategy on a playbook. When setting the strategy to free, the playbook plays tasks on each host without waiting to the others. See http://docs.ansible.com/ansible/playbooks_strategies.html.
It looks something like this (taken from the above link):
- hosts: all
strategy: free
tasks:
...
Please note that I didn’t check this and I’m very new to Ansible. I was just curious about doing what you described and happened to come acroess this strategy thing.
EDIT:
It seems like this is not exactly what you’re trying to do. Maybe “async tasks” is more appropriate as described here: http://docs.ansible.com/ansible/playbooks_async.html.
This includes specifying async and poll on a task. The following is taken from the 2nd link I mentioned:
- name: simulate long running op, allow to run for 45 sec, fire and forget
command: /bin/sleep 15
async: 45
poll: 0
I guess you can specify longer async times if your task is lengthy. You can probably define your three concurrent task this way.