Ansible Five random hosts from /etc/ansible/hosts

Question

I have this playbook, it work using max_index but always takes the first 3 hosts from /etc/ansible/hosts , i need to take 3 random (and not repeated) hosts from that file.

playbook.yml

---
- hosts: ciscos
  connection: local
  gather_facts: false
  tasks:
    - group_by: key=limited_selection
      when: play_hosts.index(inventory_hostname) < max_index | int

- hosts: limited_selection
  gather_facts: no

/etc/ansible/hosts

[ciscos]
stagin ansible_host=10.xx.xx.1
stagin2 ansible_host=10.xx.xx.1
stagin3 ansible_host=10.xx.xx.1
stagin4 ansible_host=10.xx.xx.1
stagin5 ansible_host=10.xx.xx.1

Answer 1

Solution

You need to shuffle the elements of the group and choose three first. The Jinja2 expression for that is:

(groups['ciscos'] | shuffle)[0:3]

---

Implementation which should work, but has problems

You should be able to simply filter the group in the hosts declaration:

- hosts: "{{ (groups['ciscos'] | shuffle)[0:3] }}"
  gather_facts: no
  tasks:
    - debug:

However the results are undeterministic - although the play shows as running against three randomly chosen hosts, the tasks are sometimes executed on 1, 2, 3, or 0:

PLAY [[u'stagin2', u'stagin4', u'stagin5']] *******************************************************************************

TASK [debug] **************************************************************************************************************
ok: [stagin2] => {
    "msg": "Hello world!"
}
ok: [stagin5] => {
    "msg": "Hello world!"
}

---

Workaround (implementation which works)

Use add_host module to create a filtered group:

- hosts: localhost
  connection: local
  gather_facts: no
  tasks:
    - add_host:
        name: "{{ item }}"
        groups: limited_selection
      loop:  "{{ (groups['ciscos'] | shuffle)[0:3] }}"

- hosts: limited_selection
  gather_facts: no
  tasks:
    - debug: