手写一个轮询的负载均衡算法

看了Ribbon的负载均衡算法，手写一个轮询的负载均衡算法

1.首先先把RestTemplate上的@LoadBanced去掉，使用自己的均衡算法

2.创建LoadBancer接口，方便Spring注入，方法为接收服务集群后返回其中一个服务

1 public interface LoadBalancer {
2     ServiceInstance instance(List<ServiceInstance> serviceInstances);
3 }

3.创建子类实现方法(主要思想为CAS实现轮询)

 1 @Component
 2 public class MyLoadBalancer implements LoadBalancer{
 3 
 4     private AtomicInteger atomicInteger = new AtomicInteger(0);//多线程下保证安全，记录下访问次数，并算出返回的服务下标
 5 
 6     public final int getAndIncrement() {
 7         int current;
 8         int next;
 9         do {
10             current = this.atomicInteger.get();
11             next = current >= 2147483647 ? 0 :current + 1;//防止int溢出
12         }while (!atomicInteger.compareAndSet(current, next));//CAS
13         System.out.println("*****第"+next+"次访问*****");//打印方便看效果
14         return next;
15     }
16 
17     @Override
18     public ServiceInstance instance(List<ServiceInstance> serviceInstances) {
19         int index = getAndIncrement() % serviceInstances.size();//根据第几次访问得出本次服务器下标
20         return serviceInstances.get(index);//返回
21     }
22 }

4.消费者Controller进行测试

 1 @GetMapping(value = "/test/loadbalancer")
 2     public String testLoadBalancer() {
 3         List<ServiceInstance> serviceInstances = discoveryClient.getInstances("SERVICE-NAME");
 4         if (serviceInstances == null || serviceInstances.size() <= 0) {
 5             return null;
 6         }
 7         ServiceInstance serviceInstance = loadBalancer.instance(serviceInstances);
 8         URI uri = serviceInstance.getUri();
 9         return restTemplate.getForObject(uri+"/show/serverport", String.class);
10     }

5.服务提供者显示出轮询的效果

1 @Value("${server.port}")
2 private String serverPort;
3 @GetMapping(value = "/show/serverport")
4 public String getPaymentLB() {
5     return serverPort;
6 }