code: public void proxyService(String serviceName, String contextPath) {
          if (proxiedServiceMappings().containsValue(contextPath)) {
              throw new IllegalArgumentException("Cannot proxy multiple services under the same context path");
          }
          proxiedServiceMappings.put(serviceName, contextPath);
      }
docs: Set up a load-balancing reverse proxy for the given service at the
  given context path. Requests to this proxy will be load-balanced
  among all instances of the service, as provided by our Topology.
  
  @param serviceName the name of the service to proxy
  @param contextPath the context path expose the proxy under