private void checkDB() {
		String db = config.getDatabaseProperties().getProperty(DatabaseConstants.PROP_DATABASE_TYPE).toLowerCase();
		if (!db.equals("mysql")) {
			final String dbURL = config.getDatabaseProperties().getProperty(DatabaseConstants.PROP_DATABASE_URL, "");
			checkState(dbURL.startsWith("tcp://"), "Wrong database.url configuration " + dbURL + "\n" +
					"When cluster mode is enabled, embedded H2 db can not be used. Use mysql or Use H2 TCP server");
		}
	}
check if they use MySQL in cluster mode.
ngrinder-controller/src/main/java/org/ngrinder/infra/init/ClusterConfigurationVerifier.java