Ansible: deploy on multiple hosts in the same time

By default Ansible will attempt to run on all hosts in parallel. See these Ansible docs for details. You can also use the serial parameter to limit the number of parallel hosts you want to be processed at any given time, so if you want to have a playbook run on just one host at a time you can specify serial:1, etc.

Ansible is designed so that each task will be run on all hosts before continuing on to the next task. So if you have 3 tasks it will ensure task 1 runs on all your hosts first, then task 2 is run, then task 3 is run. See this section of the Ansible docs for more details on this.

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.