In the example, we will start 2 MariaDB Galera cluster nodes communicating with each other. Each node will run in separate docker container.

Then we will setup Keycloak cluster with 2 nodes, when Keycloak node1 will use database on mariadb-node1 and Keycloak node2 will use database on mariadb-node2. Change anything in admin console of Keycloak node1, you will be immediatelly able to see the changes on keycloak node2 too, because MariaDB databases are in cluster and use multi-master synchronous replication.

This is optional step, because there is already existing docker image mposolda/mariadb-cluster, so you can just pull this image instead of building your own. So if you really follow this step and build the image by yourself, then replace all future occurences in next steps and use your image mariadb-cluster-image instead of mposolda/mariadb-cluster image.

So building image is with these command:

cd keycloak-mariadb/dockerimage
docker build -t mariadb-cluster-image .

1. Install docker of version 1.10 or later (because of docker network command to be available). Follow documentation of your OS on how to do it.

2. Create separate docker bridge network to ensure that nodes see each other through embedded DNS provided by docker.

docker network create --driver bridge mariadb_cluster

3. Run MariaDB cluster node1 with those commands:

cd keycloak-mariadb;
export KEYCLOAK_MARIADB_PATH=$(pwd);
docker run --name mariadb-node1 --net=mariadb_cluster --net-alias=docker-mariadb-node1 \
-v $KEYCLOAK_MARIADB_PATH/mariadb-conf-volume:/etc/mysql/conf.d -e MYSQL_ROOT_PASSWORD=root \
-e MYSQL_INITDB_SKIP_TZINFO=foo -e MYSQL_DATABASE=keycloak -e MYSQL_USER=keycloak -e MYSQL_PASSWORD=keycloak \
-d mposolda/mariadb-cluster:10.1 --wsrep-new-cluster;

You can check the progress of MariaDB cluster initialization by running

docker logs mariadb-node1

4. Run command to see what's the IP address of underlying docker container mariadb-node1 :

docker inspect --format '{{ .NetworkSettings.Networks.mariadb_cluster.IPAddress }}' mariadb-node1;

Then you can change your /etc/hosts and add (or update) the entry for docker-mariadb-node1 host (will be used later for datasource configuration). Replace the IP with the real IP from previous docker inspect command.

172.19.0.2 docker-mariadb-node1

5. Run MariaDB cluster node2 with those commands:

cd keycloak-mariadb;
export KEYCLOAK_MARIADB_PATH=$(pwd);
docker run --name mariadb-node2 --net=mariadb_cluster --net-alias=docker-mariadb-node2 \
-v $KEYCLOAK_MARIADB_PATH/mariadb-conf-volume:/etc/mysql/conf.d -e MYSQL_ROOT_PASSWORD=root \
-e MYSQL_INITDB_SKIP_TZINFO=foo -d mposolda/mariadb-cluster:10.1 --wsrep_cluster_address=gcomm://docker-mariadb-node1;

You can check the progress of MariaDB cluster initialization by running

docker logs mariadb-node2

6. Run command to see what's the IP address of underlying docker container mariadb-node2 :

docker inspect --format '{{ .NetworkSettings.Networks.mariadb_cluster.IPAddress }}' mariadb-node2;

Then you can change your /etc/hosts and add (or update) the entry for docker-mariadb-node2 host (will be used later for datasource configuration). Replace the IP with the real IP from previous docker inspect command.

172.19.0.3 docker-mariadb-node2

7. If you have MySQL client, you can check if state transfer from mariadb-node1 to mariadb-node2 happened correctly. Try to connect to docker-mariadb-node2 host and see if you are able to connect as "keycloak" user and see "keycloak" database.

mysql -h docker-mariadb-node2 -u keycloak -pkeycloak --execute="show databases";

The output should be like:

+--------------------+
| Database           |
+--------------------+
| information_schema |
| keycloak           |
+--------------------+

So at this moment, we have 2 MariaDB galera cluster nodes on docker-mariadb-node1 and docker-mariadb-node2 . Next step is to configure 2 Keycloak nodes when node1 will use docker-mariadb-node1 and node2 will use docker-mariadb-node2.

1. Unzip Keycloak server-distribution into directory keycloak-node1 and configure MariaDB JDBC driver version 1.3.7 as a module into module org.mariadb . See Wildfly docs for more details.

2. Configure in keycloak-node1/standalone/configuration/standalone-ha.xml the datasource MariaDB module into drivers tag like this:

<driver name="mariadb" module="org.mariadb">
    <xa-datasource-class>org.mariadb.jdbc.Driver</xa-datasource-class>
</driver>

and configure the datasource under datasources tag like this:

<datasource jndi-name="java:jboss/datasources/KeycloakDS"
            pool-name="KeycloakDS"
            enabled="true"
            use-java-context="true">
    <connection-url>jdbc:mariadb://docker-mariadb-node1/keycloak</connection-url>
    <driver>mariadb</driver>
    <security>
      <user-name>keycloak</user-name>
      <password>keycloak</password>
    </security>
</datasource>

3. Unzip another node into directory keycloak-node2 and configure again JDBC driver and standalone-ha.xml. But use docker-mariadb-node2 inside connection-url (That would be the only difference against keycloak-node1.

4. Follow other steps in Keycloak clustering documentation to ensure that keycloak-node1 and keycloak-node2 will be in cluster. Then start both nodes. Asumption is that node1 is running on virtual host node1 and node2 is running on virtual host node2.

5. Login into keycloak admin console on node1 (create user admin with password admin before) and check in Server Info in providers that connectionsJpa provider uses docker-mariadb-node1 on node1 and docker-mariadb-node2 on node2.

Assumes that 2 keycloak cluster nodes are up and running on http://node1:8080/auth and http://node2:8080/auth and user admin with password admin available on master realm, you can run the test, which creates user on node1 and checks that it's immediatelly visible on node2 etc.

1. You may need to first build Keycloak from sources (mvn clean install -DskipTests=true is sufficient) and then update version in keycloak-mariadb/mariadb-cluster-test/pom.xml.

2. Then run the test like this:

cd keycloak-mariadb/mariadb-cluster-test
mvn clean install