kolla-ansible/ansible/gather-facts.yml

---
# NOTE(awiddersheim): Gather facts for all hosts as a
# first step since several plays below require them when
# building their configurations. The below 'gather_facts'
# set to 'false' is a bit confusing but this is to avoid
# Ansible gathering facts twice.
- name: Gather facts for all hosts
  hosts: all
  serial: '{{ kolla_serial|default("0") }}'
  gather_facts: false
  tasks:
    - name: Gather facts
      setup:

    - name: Group hosts to determine when using --limit
      group_by:
        key: "all_using_limit_{{ (ansible_play_batch | length) != (groups['all'] | length) }}"
  tags: always

# NOTE(pbourke): This case covers deploying subsets of hosts using --limit. The
# limit arg will cause the first play to gather facts only about that node,
# meaning facts such as IP addresses for rabbitmq nodes etc. will be undefined
# in the case of adding a single compute node.
# NOTE(mgoddard): Divide all hosts to be queried between the hosts selected via
# the limit.
- name: Gather facts for all hosts (if using --limit)
  hosts: all_using_limit_True
  serial: '{{ kolla_serial|default("0") }}'
  gather_facts: false
  vars:
    batch_index: "{{ ansible_play_batch.index(inventory_hostname) }}"
    batch_size: "{{ ansible_play_batch | length }}"
    # Use a python list slice to divide the group up.
    # Syntax: [<start index>:<end index>:<step size>]
    delegate_hosts: "{{ groups['all'][batch_index | int::batch_size | int] }}"
  tasks:
    - name: Gather facts
      setup:
      delegate_facts: True
      delegate_to: "{{ item }}"
      with_items: "{{ delegate_hosts }}"
      # We gathered facts for all hosts in the batch during the first play.
      when: item not in ansible_play_batch
  tags: always