The galera cnf can be the same template across...

nodes.

roles/mariadb/files/galera.cnf

@@ -0,0 +1,20 @@
+[mysqld]
+binlog_format=ROW
+default-storage-engine=innodb
+innodb_autoinc_lock_mode=2
+bind-address=0.0.0.0
+
+# Galera Provider Configuration
+wsrep_on=ON
+wsrep_provider=/usr/lib/galera/libgalera_smm.so
+
+# Galera Cluster Configuration
+wsrep_cluster_name="test_cluster"
+wsrep_cluster_address="gcomm://{{ ip_node0 }},{{ ip_node1 }},{{ ip_node2 }}"
+
+# Galera Synchronization Configuration
+wsrep_sst_method=rsync
+
+# Galera Node Configuration
+wsrep_node_address="{{ listen_ip | default(ansible_default_ipv4.address) }}"
+wsrep_node_name="{{ ansible_nodename }}"

roles/mariadb/tasks/main.yml

@@ -13,9 +13,6 @@
     owner: root
     group: root
 
-- name: start service at boot.
-  command: systemctl reenable mysql.service
-
 - name: make mariadb settings volume
   file:
     path: "{{ item }}"
@@ -24,30 +21,35 @@
   with_items:
       - /srv/mariadb/lib/mysql
       - /srv/mariadb/etc/mysql
+      - /srv/mariadb/etc/mysql/conf.d
 
 - name: place settings file
   copy:
     src: files/my.cnf
-    dest: /srv/mariadb/etc/mysql
+    dest: /srv/mariadb/etc/mysql/conf.d/my.cnf
     mode: 660
 
-- name: Set galara.cnf on first node if we have at least three nodes.
-  copy:
-    src: files/galera-master.cnf
+- name: Set galara.cnf on node if we have at least three nodes.
+  template:
+    src: files/galera.cnf
     dest: /srv/mariadb/etc/mysql/conf.d/galera.cnf
     mode: 660
-  when: ansible_nodename == hostname_node0 and hostvars[groups['mariadb']]|length >= 3
-
-- name: Set galara.cnf on other nodes if we have at least three nodes.
-  copy:
-    src: files/galera-slave.cnf
-    dest: /srv/mariadb/etc/mysql/conf.d/galera.cnf
-    mode: 660
-  when: ansible_nodename != hostname_node0 and hostvars[groups['mariadb']]|length >= 3
+  when: groups['databases'] | length >= 3
 
 - command: systemctl daemon-reload
 
+- name: start service at boot.
+  command: systemctl reenable mysql.service
+
+# This mimics galera_new_cluster.sh
+- name: Initialize a new cluster.
+  command: systemctl set-environment _WSREP_NEW_CLUSTER='--wsrep-new-cluster'
+  when: groups['databases'] | length >= 3 and ansible_hostname == hostname_node0
+
 - name: make sure service is started
   systemd:
     name: mysql.service
     state: started
+
+- name: Prevent cluster re-initialization
+  command: systemctl set-environment _WSREP_NEW_CLUSTER=''

roles/mariadb/templates/mysql.service

@@ -9,10 +9,12 @@ Restart=always
 ExecStartPre=-/usr/bin/docker kill %n || /bin/true
 ExecStartPre=-/usr/bin/docker rm %n
 ExecStartPre=/usr/bin/docker pull mariadb:10.2
-ExecStart=/usr/bin/docker run  -p 3306:3306 --name %n \
+ExecStart=/usr/bin/docker run --name %n \
+ -p 3306:3306 -p 4567:4567 -p 4568:4568 -p 4444:4444 \
  -v /srv/mariadb/lib/mysql:/var/lib/mysql \
- -v /srv/mariadb/etc/mysql:/etc/mysql \
- -e MYSQL_ROOT_PASSWORD={{ secrets['MYSQL_ROOT_PASSWORD'] }} mariadb:10.2
+ -v /srv/mariadb/etc/mysql/conf.d:/etc/mysql/conf.d \
+ -e MYSQL_ROOT_PASSWORD={{ secrets['MYSQL_ROOT_PASSWORD'] }} mariadb:10.2 \
+ ${MYSQLD_OPTS} ${_WSREP_NEW_CLUSTER} ${_WSREP_START_POSITION}
 
 [Install]
 WantedBy=multi-user.target