Ansible first hostname of groups

Question

I am not sure on how to find the first ansible hostname from group_names. Could you kindly advise me on how to do it?

hosts

[webservers]
server1
server2
server3

[webserver-el7]
server4
server5
server6

And i have 2 different playbook for each host groups

playbook1.yml

- name: deploy app
  hosts: webservers
  serial: 8
  roles:
    - roles1

playbook2.yml

- name: deploy app
  hosts: webservers-el7
  serial: 8
  roles:
    - roles1

the problem is that i have delegate task to first host of each group. previously i only used webservers group, so it was much easier by using the task below

- name: syncing web files to {{ version_dir }}
  synchronize:
    src: "{{ build_dir }}"
    dest: "{{ version_dir }}"
    rsync_timeout: 60
  delegate_to: "{{ groups.webservers | first }}"

If i have 2 different group_names, how can i select the first one of each group? so it can be more dynamic

Answer 1

If you want the first host of current play to be a kind of master host to sync from, I'd recommend another approach: use one of play_hosts or ansible_play_hosts (depending on your Ansible version) variables. See magic variables.
Like delegate_to: "{{ play_hosts | first }}".

The thing is when you say hosts: webservers-el7 to Ansible webservers-el7 is a pattern here. Ansible search for hosts to match this pattern and feed them into Play. You may have written webservers-el* as well. So inside Play you don't have any variable that will tell you "I'm running this Play on hosts from group webserver-el7...". You may only make some guess work analyzing group_names and groups magic variables. But this become clumsy when you have one host in several groups.

For hosts in single group only, you may try: groups[group_names | first] | first

Answer 2

To get any element from group, use group[group_name][0...n].

This will get the first element from the group.

- debug: msg="{{ groups['group_name'][0] }}"