SpringCloud-----Ribbon手写轮询算法

爱被打了一巴掌 2023-03-01 03:15 80阅读 0赞

# 1.在服务的消费方提供一个接口 #

public interface LoadBalancer{ 
    	// serviceInstanceList 为eureka中服务的数量
        ServiceInstance instance(List<ServiceInstance> serviceInstanceList);
    
    }

# 2.实现接口 #

@Component    // 注意一定要将其注入到spring容器之中
    public class MyLb implements LoadBalancer{ 
    	// 原子类，保证多线程安全，赋予初始化值为0
        private AtomicInteger atomicInteger = new AtomicInteger(0);
    	
    	// 获取第几次访问
    	// 使用 自旋锁 和 CAS 
        private final int getAndIncrement(){ 
            int current;
            int next;
            do{ 
                current = this.atomicInteger.get();
                next = current >= Integer.MAX_VALUE ? 0 : current+1;
            }while (!this.atomicInteger.compareAndSet(current,next));
            // CAS 和内存的数据比较，没有更改，则改为期望的值
            return  next;
        }
    
        @Override
        public ServiceInstance instance(List<ServiceInstance> serviceInstanceList) { 
     		// 算法： 实际调用服务器位置下标 = rest 接口第几次请求数 % 服务器集群总个数
            int index = getAndIncrement() % serviceInstanceList.size();
            return serviceInstanceList.get(index);
        }
    }

# 3.Controller接口实现 ，记住注释@LoadBalanced #

public static  final  String PAYMENT_URL = "http://CLOUD-PAYMENT-SERVICE";
    	
        @Resource
        private DiscoveryClient discoveryClient;
    
        @Resource
        private LoadBalancer loadBalanced;
       
    	@GetMapping(value = "/consumer/payment/lb")
        public String getPaymentLB(){ 
            List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
            if(instances == null || instances.size()<=0){ 
                return null;
            }
    
            ServiceInstance serviceInstance = loadBalanced.instance(instances);
    
            URI uri = serviceInstance.getUri();
            return  restTemplate.getForObject(uri+"/payment/lb",String.class);
        }