How to create a one-time user prompt input in ansible? - ansible

Question

I have a the following oversimplified ansible playbook:
- name: Prepare worker nodes
hosts: "{{ hosts }}"
serial:
- 1
- 3
remote_user: root
any_errors_fatal: true
vars:
hosts: nodes
reboot: false
tasks:
- pause:
prompt: "Reboot server(s) to make sure things are working during setup? (Y/n)"
echo: true
register: confirm_reboot
tags: [ untagged, hostname, netplan, firewalld ]
- set_fact:
reboot: "{{ (confirm_reboot.user_input == '' or confirm_reboot.user_input == 'Y' or confirm_reboot.user_input == 'y' ) | ternary('True', 'False') }}"
tags: [ untagged, hostname, netplan, firewalld, firewalld-install, firewalld-config ]
- debug:
msg: "{{ reboot }}"
It asks for the user's input so it can decide on some reboot policies.
This works just fine when you have just one node, but when you have multiple nodes it will prompt for each one. Suppose you have 42 nodes -- it will ask you 42 times.
I'm trying to figure out if there is an easy way to make the prompt appear just once and share the result among the nodes. Maybe I have missed something in the docs?

Answer 1

Given the inventory
shell> cat hosts
[test]
host1
host2
host3
host4
host5
the playbook
shell> cat playbook.yml
---
- hosts: test
serial:
- 1
- 3
gather_facts: false
tasks:
- pause:
prompt: "Reboot? (Y/n)"
echo: true
register: confirm_reboot
run_once: true
- debug:
msg: "Reboot {{ inventory_hostname }}"
when: confirm_reboot.user_input|lower == 'y'
works as expected
shell> ansible-playbook -i hosts playbook.yml
PLAY [test] *********************************
TASK [pause] ********************************
[pause]
Reboot? (Y/n):
ok: [host1]
TASK [debug] ********************************
ok: [host1] =>
msg: Reboot host1
PLAY [test] *********************************
TASK [pause] ********************************
[pause]
Reboot? (Y/n):
ok: [host2]
TASK [debug] ********************************
ok: [host2] =>
msg: Reboot host2
ok: [host3] =>
msg: Reboot host3
ok: [host4] =>
msg: Reboot host4
PLAY [test] *********************************
TASK [pause] ********************************
[pause]
Reboot? (Y/n):
ok: [host5]
TASK [debug] ********************************
ok: [host5] =>
msg: Reboot host5
Q: "Require the input just once for the entire playbook and be propagated to all hosts."
A: Split the playbook, e.g.
shell> cat playbook.yml
---
- hosts: test
gather_facts: false
tasks:
- pause:
prompt: "Reboot? (Y/n)"
echo: true
register: confirm_reboot
run_once: true
- hosts: test
serial:
- 1
- 3
gather_facts: false
tasks:
- debug:
msg: "Reboot {{ inventory_hostname }}"
when: confirm_reboot.user_input|lower == 'y'
the variable from the first play will be shared among all hosts in the second play
shell> ansible-playbook -i hosts playbook.yml
PLAY [test] *********************************
TASK [pause] ********************************
[pause]
Reboot? (Y/n):
ok: [host1]
PLAY [test] *********************************
TASK [debug] ********************************
ok: [host1] =>
msg: Reboot host1
PLAY [test] *********************************
TASK [debug] ********************************
ok: [host3] =>
msg: Reboot host3
ok: [host2] =>
msg: Reboot host2
ok: [host4] =>
msg: Reboot host4
PLAY [test] *********************************
TASK [debug] ********************************
ok: [host5] =>
msg: Reboot host5

Answer 2

It looks like the only way this will work is by using delegate_to and delegate_facts. I came up with something like this:
- name: Prepare worker nodes
hosts: "{{ hosts }}"
serial:
- 1
- 3
remote_user: root
any_errors_fatal: true
vars:
hosts: nodes
reboot: true
pre_tasks:
- pause:
prompt: "Reboot server(s) to make sure things are working during setup? (Y/n)"
echo: true
register: confirm_reboot
run_once: true
delegate_to: localhost
delegate_facts: true
tags: [ untagged, hostname, netplan, firewalld, firewalld-install, firewalld-config ]
when: "'reboot' not in hostvars['localhost']"
- set_fact:
reboot: "{{ (confirm_reboot.user_input == '' or confirm_reboot.user_input == 'Y' or confirm_reboot.user_input == 'y' ) | ternary('True', 'False') }}"
run_once: true
delegate_to: localhost
delegate_facts: true
tags: [ untagged, hostname, netplan, firewalld, firewalld-install, firewalld-config ]
when: "'reboot' not in hostvars['localhost']"
- set_fact:
reboot: "{{ hostvars['localhost']['reboot'] }}"
run_once: true
tasks:
- debug:
msg: "{{ hostvars['localhost'] }}"
tags: [ untagged, hostname, netplan, firewalld, firewalld-install, firewalld-config ]
- debug:
msg: "{{ reboot }}"
tags: [ untagged, hostname, netplan, firewalld, firewalld-install, firewalld-config ]
This works by delegating the fact to the localhost (control node) and then it uses it by reference that seems to be kept between the different nodes. It is a hackish workaround to me, but since I don't have that much time to dig deeper into the "why", it'll have to do for now.
If anybody figures out a better way - feel free to post your answer.