1、概述
官网：https://github.com/Netflix/ribbon/wiki/Getting-Started
Ribbon目前也进入维护模式，未来替换方案：
LB（负载均衡）
集中式LB
进程内LB
Ribbon就是负载均衡+RestTemplate调用
2、Ribbon负载均衡演示
1、架构说明
总结：Ribbon其实就是一个软负载均衡的客户端组件，他可以和其他所需请求的客户端结合使用，和eureka结合只是其中的一个实例。
2、
3、二说RestTemplate的使用
官网
修改cloud-consumer-order80
getForObject方法/getForEntity方法
postForObject/postForEntity
- GET请求方法
- POST请求方法
4、依次2启动7001，7002，8001，8002，80。访问：http://localhost/consumer/payment/getForEntity/31
3、Ribbon核心组件IRule
IRule:根据特定算法从服务列表中选取一个要访问的服务
Ribbon自带负载均衡算法：
如何替换负载均衡算法：修改cloud-consumer-order80
1、注意配置细节
2、新建package
3、在myrule下面新建配置类MySelfRule
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;
@Configuration
public class MySelfRule {
@Bean(name = "myRandomRule")
public IRule myRule(){
return new RandomRule();//定义为随机
}
}4、主启动类添加@RibbonClient
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;
@SpringBootApplication
@EnableEurekaClient
@RibbonClient(name = "CLOUD-PAYMENT-SERVICE",configuration = MySelfRule.class)
public class OrderMain80 {
public static void main(String[] args) {
SpringApplication.run(OrderMain80.class);
}
}5、测试：依次启动7001，7002，8001，8002，cloud-consumer-order80
访问：http://localhost/consumer/payment/get/31
多方问几次，可以发现查询的端口号是随机的，而不是交替出现了
4、Ribbon负载均衡算法
4.1 原理 + 源码
1、注释掉cloud-consumer-order80主启动类的@RibbonClient
2、原理
3、源码：
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) {
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;
}
private int incrementAndGetModulo(int modulo) {
for (;;) {
int current = nextServerCyclicCounter.get();
int next = (current + 1) % modulo;
if (nextServerCyclicCounter.compareAndSet(current, next))
return next;
}
}4.2 手写负载均衡算法
1、修改8001，8002的controller
// 手写负载均衡需要用到
@GetMapping(value = "/payment/lb")
public String getPaymentLB(){
return serverPort;
}2、cloud-consumer-order80的ApplicationContextBean去掉@LoadBalanced
3、新建接口LoadBalancer
package com.liukai.springcloud.lb;
import org.springframework.cloud.client.ServiceInstance;
import java.util.List;
public interface LoadBalancer {
//收集服务器总共有多少台能够提供服务的机器，并放到list里面
ServiceInstance instances(List<ServiceInstance> serviceInstances);
}4、新建实现类MyLB
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;
@Component
public class MyLB implements LoadBalancer {
private AtomicInteger atomicInteger = new AtomicInteger(0);
//坐标
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)); //第一个参数是期望值，第二个参数是修改值是
System.out.print("*******第几次访问，次数next: " + next);
return next;
}
@Override
public ServiceInstance instances(List<ServiceInstance> serviceInstances) { //得到机器的列表
int index = getAndIncrement() % serviceInstances.size(); //得到服务器的下标位置
System.out.println(" ====>端口：" + serviceInstances.get(index).getPort());
return serviceInstances.get(index);
}
}5、修改OrderController
@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);
// 使用手写的负载均衡算法获取服务
ServiceInstance serviceInstance = loadBalancer.instances(instances);
// 获取服务的地址
URI uri = serviceInstance.getUri();
// 拼接地址访问
return restTemplate.getForObject(uri+"/payment/lb",String.class);
}6、测试：访问 http://localhost/consumer/payment/lb
发现访问的端口号开始轮询出现，手写负载均衡轮询算法成功
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