Fix RabbitMQ restart ordering

The host list order seen during Ansible handlers may differ to the usual
play host list order, due to race conditions in notifying handlers. This
means that restart_services.yml for RabbitMQ may be included in a
different order than the rabbitmq group, resulting in a node other than
the 'first' being restarted first. This can cause some nodes to fail to
join the cluster. The include_tasks loop was introduced in [1].

This change fixes the issue by splitting the handler into two tasks, and
restarting the first node before all others.

[1] https://review.opendev.org/c/openstack/kolla-ansible/+/763137

Change-Id: I1823301d5889589bfd48326ed7de03c6061ea5ba
Closes-Bug: #1930293

ansible/roles/rabbitmq/handlers/main.yml

@@ -1,5 +1,19 @@
 ---
-- name: Restart rabbitmq container
+# NOTE(mgoddard): These tasks perform a 'full stop upgrade', which is necessary when moving between
+# major releases. In future kolla-ansible releases we may be able to change this to a rolling
+# restart. For info on this process see https://www.rabbitmq.com/upgrade.html
+
+- name: Restart first rabbitmq container
+  vars:
+    service_name: "rabbitmq"
+    service: "{{ rabbitmq_services[service_name] }}"
+  include_tasks: 'restart_services.yml'
+  when:
+    - kolla_action != "config"
+    - inventory_hostname == groups[service.group] | first
+  listen: Restart rabbitmq container
+
+- name: Restart remaining rabbitmq containers
   vars:
     service_name: "rabbitmq"
     service: "{{ rabbitmq_services[service_name] }}"
@@ -7,4 +21,6 @@
   when:
     - kolla_action != "config"
     - inventory_hostname == item
+    - inventory_hostname != groups[service.group] | first
   loop: "{{ groups[service.group] }}"
+  listen: Restart rabbitmq container

releasenotes/notes/bug-1930293-d8a524f2070e6779.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixes more-than-2-node RabbitMQ upgrade failing randomly.
+    `LP#1930293 <https://launchpad.net/bugs/1930293>`__.