Ansible: How do I get IP address from only FQDN in Ansible? - ansible

Question

So, here's the setup.
I am passing a list of FQDN's via extra vars to the playbook, but the key of control machine are copied with their corresponding IP addresses. Also their is no specific group of these in the inventory.
The host for this playbook is a server which may or may not be part of this list that I am passing via extra vars. So, the playbook doesn't have facts of these nodes whatsoever.
So, my question is how do I get the IP addresses of the respective hosts on the fly so that I can loop over them to do some checks for some properties that I have set using their FQDN's via another playbook/ role previously. (Note: I strictly need FQDN's to set these said properties)
I have used delegate_to module, and passing FQDN's and it works but it asks if I want to continue connecting(yes/ no) and waits for user input for the initial run (if given yes, It works as expected). Is their any other simpler, cleaner way to solve this? (Note: Bare in mind I cannot modify the contents of inventory like putting alias etc)
Here is the snippet of the code:
- name: Checks
become_user: hdfs
shell: hdfs dfsadmin –report
delegate_to: "{{ item.host_name }}"
with_items:
- "{{rackDetails}}"
Here is the snippet of the master yml file where the above role is called :
- name: Checks for the property
hosts: servernode
roles:
- Checks
Inventory code snippet looks like this:
[servernode]
10.0.2.15 ansible_ssh_user=grant ansible_ssh_pass=grant
[all]
10.0.2.15 ansible_ssh_user=grant ansible_ssh_pass=grant
10.0.2.16 ansible_ssh_user=grant ansible_ssh_pass=grant
10.0.2.17 ansible_ssh_user=grant ansible_ssh_pass=grant
10.0.2.18 ansible_ssh_user=grant ansible_ssh_pass=grant
10.0.2.19 ansible_ssh_user=grant ansible_ssh_pass=grant
And finally, this is what I am passing via extra vars:
{"rackDetails":[{"host_name":"prod_node1.paas.com","rack_name":"/rack1"},{"host_name":"prod_node2.paas.com","rack_name":"/rack2"},{"host_name":"prod_node3.paas.com","rack_name":"/rack3"}]}

Answer 1

I wonder if delegate_to works if the hosts are passed as extra vars but not living inside inventory.
Anyway, you can use the dig lookup plugin:
http://docs.ansible.com/ansible/playbooks_lookups.html#the-dns-lookup-dig
{{ lookup('dig', item.host_name) }}

Answer 2

What I think you want, instead, is to convert those to FQDN's into IP addresses and put them into the -l (limit) to a playbook:
ansible-playbook my_playbook -l $( getent hosts $( cat fqdns.txt ) | cut -d' ' -f1 | tr '\n' ',' )