roles/mariadb: Use Unix socket for MariaDB tasks

Otherwise Ansible fails due to PyMySQL using a TCP connection.

See: https://github.com/ansible/ansible/issues/47736

roles/mariadb/defaults/main.yml

@@ -19,6 +19,11 @@ innodb_buffer_pool_size: 256M
 # See: https://mariadb.com/kb/en/mariadb/xtradbinnodb-server-system-variables
 innodb_buffer_pool_instances: 1
 
+# Ansible 2.7.x with PyMySQL seems to default to TCP connection so we should
+# force it to use a Unix socket.
+# See: https://github.com/ansible/ansible/issues/47736
+mariadb_login_unix_socket: /var/run/mysqld/mysqld.sock
+
 # default is 100 but the max I've seen used is 5, so let's reduce it
 max_connections: 33
 

roles/mariadb/tasks/main.yml

@@ -32,7 +32,7 @@
 # 'localhost' needs to be the last item for idempotency, see
 # https://docs.ansible.com/ansible/latest/mysql_user_module.html
 - name: Update MariaDB root password for all root accounts
-  mysql_user: name=root host={{ item }} password={{ mariadb_root_password }}
+  mysql_user: name=root host={{ item }} password={{ mariadb_root_password }} login_unix_socket={{ mariadb_login_unix_socket }}
   loop:
     - "{{ inventory_hostname }}"
     - 127.0.0.1

roles/mariadb/templates/.my.cnf.j2

@@ -1,3 +1,4 @@
 [client]
 user=root
 password='{{ mariadb_root_password }}'
+login_unix_socket='{{ mariadb_login_unix_socket }}'