code: public static void shutdownCluster(Cluster cluster) {
      synchronized (clusters) {
        String clusterName = cluster.getName();
        if (clusters.get(clusterName) != null ) {
          cluster.getConnectionManager().shutdown();
          clusters.remove(clusterName);
        }
      }
    }
docs: Shutdown this cluster, removing it from the Map. This operation is
  extremely expensive and should not be done lightly.
  @param cluster