Wait for MariaDB to be accessible via HAProxy

Explicitly wait for the database to be accessible via the load balancer.
Sometimes it can reject connections even when all database services are up,
possibly due to the health check polling in HAProxy.

Closes-Bug: #1840145
Change-Id: I7601bb710097a78f6b29bc4018c71f2c6283eef2
(cherry picked from commit 03cd7eb356)

ansible/roles/mariadb/tasks/recover_cluster.yml

@@ -227,3 +227,5 @@
   when:
     - bootstrap_host is defined
     - bootstrap_host != inventory_hostname
+
+- import_tasks: wait_for_loadbalancer.yml

ansible/roles/mariadb/tasks/register.yml

@@ -14,6 +14,8 @@
       priv: "*.*:USAGE"
   run_once: True
 
+- import_tasks: wait_for_loadbalancer.yml
+
 - name: Creating the Mariabackup database
   become: true
   kolla_toolbox:

ansible/roles/mariadb/tasks/wait_for_loadbalancer.yml

@@ -0,0 +1,16 @@
+---
+# Explicitly wait for the database to be accessible via the load balancer.
+# Sometimes it can reject connections even when all database services are up,
+# due to the health check polling in HAProxy.
+- name: wait for MariaDB to be available via HAProxy
+  wait_for:
+    host: "{{ database_address }}"
+    port: "{{ database_port }}"
+    connect_timeout: 1
+    timeout: 60
+    search_regex: "MariaDB"
+  register: check_mariadb_port
+  until: check_mariadb_port is success
+  retries: 10
+  delay: 6
+  run_once: True