Introduction to Spring Cloud Rest Client with Netflix Ribbon – 使用Netflix Ribbon的Spring Cloud Rest Client介绍

最后修改: 2016年 11月 10日


1. Introduction


Netflix Ribbon is an Inter Process Communication (IPC) cloud library. Ribbon primarily provides client-side load balancing algorithms.

Netflix Ribbon是一个进程间通信(IPC)云库。Ribbon主要提供客户端的负载平衡算法。

Apart from the client-side load balancing algorithms, Ribbon provides also other features:


  • Service Discovery Integration – Ribbon load balancers provide service discovery in dynamic environments like a cloud. Integration with Eureka and Netflix service discovery component is included in the ribbon library
  • Fault Tolerance – the Ribbon API can dynamically determine whether the servers are up and running in a live environment and can detect those servers that are down
  • Configurable load-balancing rules – Ribbon supports RoundRobinRule, AvailabilityFilteringRule, WeightedResponseTimeRule out of the box and also supports defining custom rules

Ribbon API works based on the concept called “Named Client”. While configuring Ribbon in our application configuration file we provide a name for the list of servers included for the load balancing.

Ribbon API的工作原理是基于 “命名客户 “的概念。在我们的应用程序配置文件中配置Ribbon时,我们提供了一个用于负载平衡的服务器列表的名称。

Let’s take it for a spin.


2. Dependency Management


The Netflix Ribbon API can be added to our project by adding the below dependency to our pom.xml:

通过在我们的pom.xml中添加以下依赖关系,Netflix Ribbon API可以被添加到我们的项目中:


The latest libraries can be found here.


3. Example Application


In order to see the working of Ribbon API, we build a sample microservice application with Spring RestTemplate and we enhance it with Netflix Ribbon API along with Spring Cloud Netflix API.

为了了解Ribbon API的工作情况,我们用Spring RestTemplate构建了一个样本微服务应用程序,并利用Netflix Ribbon API和Spring Cloud Netflix API对其进行了强化。

We’ll use one of Ribbon’s load-balancing strategies, WeightedResponseTimeRule, to enable the client side load balancing between 2 servers, which are defined under a named client in the configuration file, in our application.


4. Ribbon Configuration


Ribbon API enables us to configure the following components of the load balancer:

Ribbon API使我们能够配置负载平衡器的以下组件。

  • Rule – Logic component which specifies the load balancing rule we are using in our application
  • Ping – A Component which specifies the mechanism we use to determine the server’s availability in real-time
  • ServerList – can be dynamic or static. In our case, we are using a static list of servers and hence we are defining them in the application configuration file directly

Let write a simple configuration for the library:


public class RibbonConfiguration {

    IClientConfig ribbonClientConfig;

    public IPing ribbonPing(IClientConfig config) {
        return new PingUrl();

    public IRule ribbonRule(IClientConfig config) {
        return new WeightedResponseTimeRule();

Notice how we used the WeightedResponseTimeRule rule to determine the server and PingUrl mechanism to determine the server’s availability in real-time.


According to this rule, each server is given a weight according to its average response time, lesser the response time gives lesser the weight. This rule randomly selects a server where the possibility is determined by server’s weight.


And the PingUrl will ping every URL to determine the server’s availability.


5. application.yml


Below is the application.yml configuration file we created for this sample application:


    name: spring-cloud-ribbon

  port: 8888

      enabled: false
    listOfServers: localhost:9092,localhost:9999
    ServerListRefreshInterval: 15000

In the above file, we specified:


  • Application name
  • Port number of the application
  • Named client for the list of servers: “ping-server”
  • Disabled Eureka service discovery component, by setting eureka: enabled to false
  • Defined the list of servers available for load balancing, in this case, 2 servers
  • Configured the server refresh rate with ServerListRefreshInterval

6. RibbonClient


Let’s now set up the main application component snippet – where we use the RibbonClient to enable the load balancing instead of the plain RestTemplate:


  name = "ping-a-server",
  configuration = RibbonConfiguration.class)
public class ServerLocationApp {

    RestTemplate restTemplate;

    public String serverLocation() {
        return this.restTemplate.getForObject(
          "http://ping-server/locaus", String.class);

    public static void main(String[] args) {, args);

And here’s the RestTemplate configuration:


public class RestTemplateConfiguration{
    RestTemplate getRestTemplate() {
        return new RestTemplate();

We defined a controller class with the annotation @RestController; we also annotated the class with @RibbonClient with a name and a configuration class.


The configuration class we defined here is the same class that we defined before in which we provided the desired Ribbon API configuration for this application.

我们在这里定义的配置类与之前定义的类相同,在该类中我们为这个应用程序提供了所需的Ribbon API配置。

Notice we annotated the RestTemplate with @LoadBalanced which suggests that we want this to be load balanced and in this case with Ribbon.


7. Failure Resiliency in Ribbon


As we discussed earlier in this article, Ribbon API not only provides client side load balancing algorithms but also it has built in failure resiliency.

正如我们在本文前面所讨论的,Ribbon API不仅提供了客户端的负载平衡算法,而且它还内置了故障恢复能力。

As stated before, Ribbon API can determine the server’s availability through the constant pinging of servers at regular intervals and has a capability of skipping the servers which are not live.

如前所述,Ribbon API可以通过定期对服务器进行不断的ping来确定服务器的可用性,并有能力跳过不在线的服务器。

In addition to that, it also implements Circuit Breaker pattern to filter out the servers based on specified criteria.

除此之外,它还实现了Circuit Breaker模式,根据指定标准过滤掉服务器。

The Circuit Breaker pattern minimizes the impact of a server failure on performance by swiftly rejecting a request to that server that is failing without waiting for a time-out. We can disable this Circuit Breaker feature by setting the property niws.loadbalancer.availabilityFilteringRule.filterCircuitTripped to false.

Circuit Breaker 模式通过迅速拒绝对该故障服务器的请求而不等待超时,将服务器故障对性能的影响降到最低。我们可以通过将属性niws.loadbalancer.availabilityFilteringRule.filterCircuitTripped设为false来禁用这个Circuit Breaker功能。

When all servers are down, thus no server is available to serve the request, the pingUrl() will fail and we receive an exception java.lang.IllegalStateException with a message “No instances are available to serve the request”.


8. Conclusion


In this article, we discussed Netflix Ribbon API and its implementation in a simple sample application.

在这篇文章中,我们讨论了Netflix Ribbon API以及它在一个简单的示例应用程序中的实现。

The complete source code for the example described above can be found on the GitHub repository.