code: @Override
  	@Nullable
  	public String getMetricQueryServiceGatewayRpcAddress() {
  		if (queryService != null) {
  			return queryService.getSelfGateway(MetricQueryServiceGateway.class).getAddress();
  		} else {
  			return null;
  		}
  	}
docs: Returns the address under which the {@link MetricQueryService} is reachable.
  
  @return address of the metric query service