0、前言

这是学习尚硅谷 spring cloud中遇到的一个坑 多看文档地址：[文档地址][https://docs.spring.io/spring-cloud-commons/docs/current/reference/html/#custom-loadbalancer-configuration]

1、spring cloud 2020.0.1 LoadBalancer负载均衡算法切换

springcloud 2020.0.1 版本之后 删除了eureka中的ribbon，替代ribbon的是spring cloud自带的LoadBalancer，默认使用的是轮询的方式

如果切换，需要我们进行配置

我们这里使用的是restTemplate作为访问工具

1.1 首先定义一个CustomLoadBalancerConfiguration.class 这个包可以在主启动类所在包及其子包下 这一点和ribbon不同

package com.peach.springcloud.config;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.core.env.Environment;

//这里 不需要 @configuration注解  不需要 不需要
public class CustomLoadBalancerConfiguration {

    @Bean
    ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,
                                                            LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);

        return new RandomLoadBalancer(loadBalancerClientFactory
                .getLazyProvider(name, ServiceInstanceListSupplier.class),
                name);
    }
}

1.2 之后在我们注入restTemplate的地方使用注解@LoadBalancerClients 或者@LoadBalancerClient注解进行配置

package com.peach.springcloud.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
//在这里配置我们自定义的LoadBalancer策略 如果有大佬想自己扩展算法 需要实现ReactorServiceInstanceLoadBalancer接口
//@LoadBalancerClients(defaultConfiguration = {name = "CLOUD-PAYMENT-SERVICE", configuration = CustomLoadBalancerConfiguration.class})
//注意这里的name属性 需要和eureka页面中的服务提供者名字一直 此时页面中是大写
@LoadBalancerClient(name = "CLOUD-PAYMENT-SERVICE",configuration = CustomLoadBalancerConfiguration.class)
public class ApplicationContextConfig {

    //将这个对象放入ioc容器
    @Bean
    @LoadBalanced  //使用这个注解给restTemplate赋予了负载均衡的能力
    public RestTemplate getRestTemplate(){
        return new RestTemplate();
    }
}

注意@LoadBalancerClients 或者@LoadBalancerClient注解中的name或者value属性一定要和eureka中注册的服务名一致 大小写一定要一致

1.3 之后访问页面就可以看到了

1.4 自定义负载均衡算法

我的做法很简单 看源码的RoundRobinLoadBalancer的实现 copy一下在最后选择的时候改变一下策略即可 看下面代码中的注释

package com.peach.springcloud.config;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.DefaultResponse;
import org.springframework.cloud.client.loadbalancer.EmptyResponse;
import org.springframework.cloud.client.loadbalancer.Request;
import org.springframework.cloud.client.loadbalancer.Response;
import org.springframework.cloud.loadbalancer.core.*;
import reactor.core.publisher.Mono;

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

//这个方法基本是copy的RoundRobinLoadBalancer自己改一改出来的
public class PeachLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    private static final Log log = LogFactory.getLog(RoundRobinLoadBalancer.class);

    final AtomicInteger position;//请求的次数

    final String serviceId; //服务名称 用于提示报错信息的

    private int flag = 0; //自己定义的计数器

    //两个参数的构造方法 需要服务名称和实例提供者 这个在方法中传递进来
    public PeachLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider,
                                  String serviceId) {
        //如果不传人请求次数就自己初始化 反正每次都+1
        this(new Random().nextInt(1000), serviceId,serviceInstanceListSupplierProvider);
    }

    public PeachLoadBalancer(int seedPosition, String serviceId, ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
        this.position = new AtomicInteger(seedPosition);
        this.serviceId = serviceId;
        this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
    }

    ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        //从服务提供者中获取到当前request请求中的serviceInstances并且遍历
        ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider
                .getIfAvailable(NoopServiceInstanceListSupplier::new);
        return supplier.get(request).next()
                .map(serviceInstances -> processInstanceResponse(supplier, serviceInstances));
    }

    private Response<ServiceInstance> processInstanceResponse(ServiceInstanceListSupplier supplier,
                                                              List<ServiceInstance> serviceInstances) {
        Response<ServiceInstance> serviceInstanceResponse = getInstanceResponse(serviceInstances);
        if (supplier instanceof SelectedInstanceCallback && serviceInstanceResponse.hasServer()) {
            ((SelectedInstanceCallback) supplier).selectedServiceInstance(serviceInstanceResponse.getServer());
        }
        return serviceInstanceResponse;
    }

    private Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances) {
        if (instances.isEmpty()) {
            if (log.isWarnEnabled()) {
                log.warn("No servers available for service: " + serviceId);
            }
            return new EmptyResponse();
        }
        //pos是当前请求的次数 这样可以自定义负载均衡的切换  这个每次+1的操作是复制的 最好是不删
        int pos = Math.abs(this.position.incrementAndGet());

        if (pos%4==0){
            //是4的倍数就切换
            flag += 1;
        }
        if (flag >= instances.size()){
            flag = 0;
        }
        //主要的就是这句代码设置负载均衡切换
        ServiceInstance instance = instances.get(flag);
        return new DefaultResponse(instance);
    }
}

1.5之后在配置的地方也就是CustomLoadBalancerConfiguration配置类中返回我们自己的方案即可

package com.peach.springcloud.config;

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.core.env.Environment;

public class CustomLoadBalancerConfiguration {

    @Bean
    ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,
                                                            LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);

//        这里返回了新的randomLoadBalancer

        //这里返回了我自己定义的方法
        return new PeachLoadBalancer(loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
//        return new RandomLoadBalancer(loadBalancerClientFactory
//                .getLazyProvider(name, ServiceInstanceListSupplier.class),
//                name);
    }
}

1.6 之后访问页面就可以看到了