@VisibleForTesting
    ServerStats getServerStats(Server server) {
        return lbContext.getServerStats(server);
    }
Subject an operation to run in the load balancer

@param request
@param errorHandler
@param requestConfig
@param rxClientConfig
@return
ribbon-transport/src/main/java/com/netflix/ribbon/transport/netty/http/LoadBalancingHttpClient.java