Ribbon客户端负载均衡算法分析

一、源码分析

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.netflix.loadbalancer;public interface IRule {Server choose(Object var1);void setLoadBalancer(ILoadBalancer var1);ILoadBalancer getLoadBalancer();
}

轮询负载均衡算法

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.netflix.loadbalancer;import com.netflix.client.config.IClientConfig;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;public class RoundRobinRule extends AbstractLoadBalancerRule {private AtomicInteger nextServerCyclicCounter;private static final boolean AVAILABLE_ONLY_SERVERS = true;private static final boolean ALL_SERVERS = false;private static Logger log = LoggerFactory.getLogger(RoundRobinRule.class);public RoundRobinRule() {this.nextServerCyclicCounter = new AtomicInteger(0);}public RoundRobinRule(ILoadBalancer lb) {this();this.setLoadBalancer(lb);}public Server choose(ILoadBalancer lb, Object key) {if (lb == null) {log.warn("no load balancer");return null;} else {Server server = null;int count = 0;while(true) {if (server == null && count++ < 10) {List<Server> reachableServers = lb.getReachableServers();List<Server> allServers = lb.getAllServers();int upCount = reachableServers.size();int serverCount = allServers.size(); //服务器集群总数if (upCount != 0 && serverCount != 0) {int nextServerIndex = this.incrementAndGetModulo(serverCount);server = (Server)allServers.get(nextServerIndex);if (server == null) {Thread.yield();} else {if (server.isAlive() && server.isReadyToServe()) {return server;}server = null;}continue;}log.warn("No up servers available from load balancer: " + lb);return null;}if (count >= 10) {log.warn("No available alive servers after 10 tries from load balancer: " + lb);}return server;}}}private int incrementAndGetModulo(int modulo) {int current;int next;do {current = this.nextServerCyclicCounter.get();next = (current + 1) % modulo;} while(!this.nextServerCyclicCounter.compareAndSet(current, next));return next;}public Server choose(Object key) {return this.choose(this.getLoadBalancer(), key);}public void initWithNiwsConfig(IClientConfig clientConfig) {}
}

二、手写Ribbon轮询算法

package com.george.springcloud.lb;import org.springframework.cloud.client.ServiceInstance;import java.util.List;/*** @author Yang Hao* @description* @date 2020-09-16 14:58*/
public interface MyLoadBalancer {ServiceInstance instances(List<ServiceInstance> serviceInstances);
}

package com.george.springcloud.lb.impl;import com.george.springcloud.lb.MyLoadBalancer;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;/*** @author Yang Hao* @description* @date 2020-09-16 15:00*/
@Component //让容器扫描到这个类
public class MyLoadBalancerImpl implements MyLoadBalancer {private AtomicInteger atomicInteger = new AtomicInteger(0);/*** 参考RoundRobinRule 类的源码实现 自定义选择规则** @return*/public final int getAndIncrement() {int current;int next;do {current = this.atomicInteger.get();//Integer 最大值2147483647next = current >= 2147483647 ? 0 : current + 1;} while (!this.atomicInteger.compareAndSet(current, next));System.out.println("---------第几次访问,次数:next=" + next);return next;}/*** 负载均衡算法: rest接口第几次请求数%服务器集群总数量=实际调用服务器位置下标.每次服务重启动后rest接口计数从1开始。** @param serviceInstances* @return*/@Overridepublic ServiceInstance instances(List<ServiceInstance> serviceInstances) {int index = getAndIncrement() % serviceInstances.size();return serviceInstances.get(index);}
}

    @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 = myLoadBalancer.instances(instances);URI uri = serviceInstance.getUri();return restTemplate.getForObject(uri + "/payment/lb", String.class);}

不知道这里为啥会报这个错

通过postman请求都是正常的

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Ribbon客户端负载均衡算法分析

一、源码分析

二、手写Ribbon轮询算法

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