《SpringCloud专题12》-微服务架构编码构建-手写Ribbon负载均衡器

1.前言

Ribbon是SpringCloud的负载均衡器，默认的算法是轮询。在这里为了方便负载均衡的原理，可以自己手写一个负载均衡器

2.自定义一个本地负载均衡器

2.1.ApplicationContextBean去掉注解@LoadBalanced

package com.itxiongmao.config;

/**
 * @BelongsProject: springcloud2020
 * @BelongsPackage: com.itxiongmao.config
 * @CreateTime: 2020-07-09 12:27
 * @Description: TODO
 */
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class ApplicationContextConfig {

    @Bean
    //@LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }
}

2.2.LoadBalancer接口

package com.itxiongmao.lb;

import org.springframework.cloud.client.ServiceInstance;

import java.util.List;

public interface LoadBalaner {

    ServiceInstance instance(List<ServiceInstance> instances);
}

2.3.MyLB

package com.itxiongmao.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 LoadBalaner {

    private AtomicInteger atomicInteger = new AtomicInteger(0);

    public final int getIncrement() {
        int current;
        int next;
        do {
            current = this.atomicInteger.get();
            next = 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;
    }

    @Override
    public ServiceInstance instance(List<ServiceInstance> instances) {
        int index = getIncrement() % instances.size();
        return instances.get(index);
    }
}

2.5.OrderController

@Resource
    private DiscoveryClient discoveryClient;

    @Resource
    private LoadBalaner loadBalaner;

    @GetMapping("payment/lb/selectOne/{id}")
    public String getPaymentLB(@PathVariable("id") long id) {
        List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        if (instances == null || instances.size() == 0) {
            return null;
        }
        ServiceInstance serviceInstance = loadBalaner.instance(instances);
        URI uri = serviceInstance.getUri();
        return restTemplate.getForObject(uri + "/payment/get", String.class);
    }

2.6.测试