Remove serialized collect of ansible_default_ipv4

The fallback_ips tasks are essentially serializing the gathering of one
fact on all the hosts, which can have dramatic performance implications
on large clusters (several minutes).

This is essentially a reversal of 35f248dff0
Being able to run without refreshing the cache facts is not worth it.

We keep fallback_ip for now, simply changing the access to a normal
hostvars variable instead of a custom dictionnary.

roles/kubespray-defaults/tasks/fallback_ips.yml

@@ -1,35 +0,0 @@
----
-# Set 127.0.0.1 as fallback IP if we do not have host facts for host
-# ansible_default_ipv4 isn't what you think.
-# Thanks https://medium.com/opsops/ansible-default-ipv4-is-not-what-you-think-edb8ab154b10
-
-- name: Gather ansible_default_ipv4 from all hosts or specific hosts
-  setup:
-    gather_subset: '!all,network'
-    filter: "ansible_default_ipv4"
-  delegate_to: "{{ item }}"
-  delegate_facts: true
-  when: hostvars[item].ansible_default_ipv4 is not defined
-  loop: "{{ (ansible_play_hosts_all + [groups['kube_control_plane'][0]]) | unique if ansible_limit is defined else (groups['k8s_cluster'] | default([]) + groups['etcd'] | default([]) + groups['calico_rr'] | default([])) | unique }}"
-  run_once: true
-  ignore_unreachable: true
-  tags: always
-
-- name: Create fallback_ips_base
-  set_fact:
-    fallback_ips_base: |
-      ---
-      {% set search_hosts = (ansible_play_hosts_all + [groups['kube_control_plane'][0]]) | unique if ansible_limit is defined else (groups['k8s_cluster'] | default([]) + groups['etcd'] | default([]) + groups['calico_rr'] | default([])) | unique %}
-      {% for item in search_hosts %}
-      {% set found = hostvars[item].get('ansible_default_ipv4') %}
-      {{ item }}: "{{ found.get('address', '127.0.0.1') }}"
-      {% endfor %}
-  delegate_to: localhost
-  connection: local
-  delegate_facts: true
-  become: false
-  run_once: true
-
-- name: Set fallback_ips
-  set_fact:
-    fallback_ips: "{{ hostvars.localhost.fallback_ips_base | from_yaml }}"

roles/kubespray-defaults/tasks/main.yaml

@@ -3,9 +3,20 @@
   tags:
     - always
   block:
-    - name: Set fallback_ips
-      import_tasks: fallback_ips.yml
-      when: fallback_ips is not defined
+    - name: Gather ansible_default_ipv4
+      setup:
+        gather_subset: '!all,network'
+        filter: "ansible_default_ipv4"
+      when: ansible_default_ipv4 is not defined
+      ignore_unreachable: true
+      # Set 127.0.0.1 as fallback IP if we do not have host facts for host
+      # ansible_default_ipv4 isn't what you think.
+      # https://medium.com/opsops/ansible-default-ipv4-is-not-what-you-think-edb8ab154b10
+      # TODO: discard this and update all the location relying on it in "looping on hostvars" templates
+    - name: Set fallback_ip
+      set_fact:
+        fallback_ip: "{{ ansible_default_ipv4.address | d('127.0.0.1') }}"
+      when: fallback_ip is not defined
 
     - name: Set no_proxy
       import_tasks: no_proxy.yml

roles/kubespray-defaults/tasks/no_proxy.yml

@@ -13,7 +13,7 @@
       {% set cluster_or_control_plane = 'k8s_cluster' %}
       {%- endif -%}
       {%- for item in (groups[cluster_or_control_plane] + groups['etcd'] | default([]) + groups['calico_rr'] | default([])) | unique -%}
-      {{ hostvars[item]['access_ip'] | default(hostvars[item]['ip'] | default(fallback_ips[item])) }},
+      {{ hostvars[item]['access_ip'] | default(hostvars[item]['ip'] | default(hostvars[item]['fallback_ip'])) }},
       {%- if item != hostvars[item].get('ansible_hostname', '') -%}
       {{ hostvars[item]['ansible_hostname'] }},
       {{ hostvars[item]['ansible_hostname'] }}.{{ dns_domain }},