package com.liukai.myrule;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @author liukai
 * @version 1.0.0
 * @ClassName MySelfRule.java
 * @Description TODO
 * @createTime 2021年03月21日 11:50:00
 */
@Configuration
public class MySelfRule {

 @Bean(name = "myRandomRule")
 public IRule myRule(){
  return new RandomRule();//定義為隨機
 }
}

package com.liukai.springcloud;

import com.liukai.myrule.MySelfRule;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.ribbon.RibbonClient;

/**
 * @author liukai
 * @version 1.0.0
 * @ClassName OrderMain80.java
 * @Description TODO
 * @createTime 2021年03月19日 18:27:00
 */
@SpringBootApplication
@EnableEurekaClient
@RibbonClient(name = "CLOUD-PAYMENT-SERVICE",configuration = MySelfRule.class)
public class OrderMain80 {

 public static void main(String[] args) {
   SpringApplication.run(OrderMain80.class);
 }

}

 public Server choose(ILoadBalancer lb, Object key) {
  if (lb == null) {
   log.warn("no load balancer");
   return null;
  }

  Server server = null;
  int count = 0;
  while (server == null && count++ < 10) {
   List<Server> reachableServers = lb.getReachableServers();
   List<Server> allServers = lb.getAllServers();
   int upCount = reachableServers.size();
   int serverCount = allServers.size();

   if ((upCount == 0) || (serverCount == 0)) {
    log.warn("No up servers available from load balancer: " + lb);
    return null;
   }

   int nextServerIndex = incrementAndGetModulo(serverCount);
   server = allServers.get(nextServerIndex);

   if (server == null) {
    /* Transient. */
    Thread.yield();
    continue;
   }

   if (server.isAlive() && (server.isReadyToServe())) {
    return (server);
   }

   // Next.
   server = null;
  }

  if (count >= 10) {
   log.warn("No available alive servers after 10 tries from load balancer: "
     + lb);
  }
  return server;
 }

 /**
  * Inspired by the implementation of {@link AtomicInteger#incrementAndGet()}.
  *
  * @param modulo The modulo to bound the value of the counter.
  * @return The next value.
  */
 private int incrementAndGetModulo(int modulo) {
  for (;;) {
   int current = nextServerCyclicCounter.get();
   int next = (current + 1) % modulo;
   if (nextServerCyclicCounter.compareAndSet(current, next))
    return next;
  }
 }

// 手寫負載均衡需要用到
 @GetMapping(value = "/payment/lb")
 public String getPaymentLB(){
  return serverPort;
 }

package com.liukai.springcloud.lb;

import org.springframework.cloud.client.ServiceInstance;

import java.util.List;

/**
 * @author liukai
 * @version 1.0.0
 * @ClassName LoadBalancer.java
 * @Description TODO
 * @createTime 2021年03月21日 12:24:00
 */
public interface LoadBalancer {
 //收集服務(wù)器總共有多少臺能夠提供服務(wù)的機器，并放到list里面
 ServiceInstance instances(List<ServiceInstance> serviceInstances);
}

package com.liukai.springcloud.lb;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author liukai
 * @version 1.0.0
 * @ClassName MyLB.java
 * @Description TODO
 * @createTime 2021年03月21日 12:27:00
 */
@Component
public class MyLB implements LoadBalancer {

 private AtomicInteger atomicInteger = new AtomicInteger(0);

 //坐標
 private final int getAndIncrement() {
  int current;
  int next;
  do {
   current = this.atomicInteger.get();
   next = current >= 2147483647 ? 0 : current + 1;
  } while (!this.atomicInteger.compareAndSet(current, next)); //第一個參數(shù)是期望值，第二個參數(shù)是修改值是
  System.out.print("*******第幾次訪問，次數(shù)next: " + next);
  return next;
 }



 @Override
 public ServiceInstance instances(List<ServiceInstance> serviceInstances) { //得到機器的列表
  int index = getAndIncrement() % serviceInstances.size(); //得到服務(wù)器的下標位置
  System.out.println(" ====>端口：" + serviceInstances.get(index).getPort());
  return serviceInstances.get(index);
 }
}

@Resource
 private LoadBalancer loadBalancer;

 @Resource
 private DiscoveryClient discoveryClient;

 @GetMapping(value = "/consumer/payment/lb")
 public String getPaymentLB(){
  List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
  if (instances == null || instances.size() <= 0){
   return null;
  }
//  instances.forEach(System.out::println);
  // 使用手寫的負載均衡算法獲取服務(wù)
  ServiceInstance serviceInstance = loadBalancer.instances(instances);
  // 獲取服務(wù)的地址
  URI uri = serviceInstance.getUri();
  // 拼接地址訪問
  return restTemplate.getForObject(uri+"/payment/lb",String.class);
 }