code: @Override
  	protected Object getHandler(String serviceName) {
  		Object handler = handlerMap.get(serviceName);
  		if (handler == null) {
  			logger.error("Service '{}' is not registered in this multi-server", serviceName);
  			throw new RuntimeException("Service '" + serviceName + "' does not exist");
  		}
  		return handler;
  	}
docs: Get the handler (object) that should be invoked to execute the specified
  RPC method based on the specified service name.
  
  @param serviceName the service name
  @return the handler to invoke the RPC call against