Running a playbook on multiple host groups one at a time

Question

I want to run a playbook containing some roles on multiple host groups I create dynamically with the group_by module.

I'm able to do it like the example below (ping replacing my actual role).

I was wondering if there is a way to run each group separately in a loop instead of listing all instance ids. I don't want to create a duplicate line with every instance id.

The purpose here is to deploy to one instance in every data center at a time instead of running all with a low serial which takes a long time.

There might be a different way of doing it, I don't want to create static groups in the inventory for each instance_id as well.

---
- hosts: tag_type_edgenode
  tasks:
    - group_by: key=instance_id_{{instance_id}}
      register: dyn_groups

- hosts: instance_id_1
  tasks:
    - ping:
- hosts: instance_id_2
  tasks:
    - ping:
- hosts: instance_id_3
  tasks:
    - ping:
- hosts: instance_id_4
  tasks:
    - ping:

Answer 1

There is a simpler method using the size (length) of each group. However, this runs on all members of a group, flowing through the groups sequentially. I think OP was asking for how to act on the first member of each group, which I am also working on figuring out.

- name: "Restore selected devices in model_dc"
  hosts: group_1, group_2, group_3, group_4, group_5, group_6, group_7, !excluded
  any_errors_fatal: true    # Stop entire play if one host fails
  gather_facts: no
  order: inventory
  serial: 
    - "{{ groups['group_1'] | length }}" # The number of hosts for first batch
    - "{{ groups['group_2'] | length }}" # The number of hosts for second batch
    - "{{ groups['group_3'] | length }}"
    - "{{ groups['group_4'] | length }}"
    - "{{ groups['group_5'] | length }}"
    - "{{ groups['group_6'] | length }}"
    - "{{ groups['group_7'] | length }}" # The number of hosts for every batch until the end.