Spring Cloud入门系列（六）——负载均衡之Ribbon

概述

负载均衡

集中式LB

进程内LB

架构说明

其实ribbon已经被Eureka整合进去了。

RestTemplate

Ribbon的负载策略

IRule是Ribbon实现负载均衡的顶层接口。

自定义策略

在80端口，新增com.banana.rule.MyRule文件

MyRule

package com.banana.rule;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
 * @author layman
 * @description: 自定义ribbon的负载均衡配置类
 */
@Configuration
public class MyRule {
    
    
    @Bean
    public IRule myRule(){
    
    
        //切换为随机模式
        return new RandomRule();
    }
}

主启动类上添加 @RibbonClient注解

@RibbonClient(name = "CLOUD-PAYMENT-SERVICE", configuration = MyRule.class)

package com.banana.springcloud;

import com.banana.rule.MyRule;
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 layman
 * @date 2021/1/9
 */
@SpringBootApplication
@EnableEurekaClient
@RibbonClient(name = "CLOUD-PAYMENT-SERVICE", configuration = MyRule.class)
public class OrderMain80 {
    
    
    public static void main(String[] args) {
    
    
            SpringApplication.run(OrderMain80.class,args);
        }
}

默认策略的源码解读

https://blog.csdn.net/single_0910/article/details/112696676

自定义轮询算法

80端口改造

package com.banana.springcloud.loadbalancer;

import org.springframework.cloud.client.ServiceInstance;

import java.util.List;

/**
 * 自定义LoadBalancer
 * @author layman
 * @date 2021/1/16
 */
public interface MyLoadBalancer {
    
    

    /**
    * 获取可用的服务实例
    * @param instances：服务列表
    * @return 单个的服务
    */
    ServiceInstance getInstance(List<ServiceInstance> instances);
}

package com.banana.springcloud.loadbalancer.impl;

import com.banana.springcloud.loadbalancer.MyLoadBalancer;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;

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

/**
 * 自定义轮询策略
 * @author layman
 * @date 2021/1/16
 */
@Component
public class MyLoadBalancerImpl implements MyLoadBalancer {
    
    

    private AtomicInteger nextServerCounter =  new AtomicInteger(0);

    public final int getAndIncrement(){
    
    
        int current;
        int next;
        do{
    
    
            current = nextServerCounter.get();
            next = (current > Integer.MAX_VALUE ? 0 : current + 1);
        }while(!this.nextServerCounter.compareAndSet(current,next));
        System.out.println("--------次数next的值--------:"+next);
        return next;
    }
    @Override
    public ServiceInstance getInstance(List<ServiceInstance> instances) {
    
    
        int index = getAndIncrement() % instances.size();
        return instances.get(index);
    }
}

80端口的OrderController

	@Resource
    private MyLoadBalancer myLoadBalancer;
    
	@GetMapping("/LoadBalancer")
    public String discovery(){
    
    
        //获取对应名称的所有server数量
        List<ServiceInstance> instances = discoveryClient.getInstances("cloud-payment-service");
        if(instances ==null || instances.size() <=0){
    
    
            return null;
        }
        ServiceInstance server = myLoadBalancer.getInstance(instances);
        URI uri = server.getUri();
        String object = restTemplate.getForObject(uri + "/payment/LoadBalancer", String.class);
        return object;
    }