一、Spring Cloud LoadBalancer介绍

Spring Cloud LoadBalancer是Spring Cloud官网提供的一个客户端负载均衡器，功能类似于Ribbon。在Spring Cloud Nacos 2021移除了中Ribbon组件，Spring Cloud在Spring Cloud Commons项目中，添加了Spring Cloud Loadbalancer作为新的负载均衡器。

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-loadbalancer</artifactId>
</dependency>

二、LoadBalancer负载均衡策略

LoadBalancer的负载均衡策略没有 Ribbon 那么丰富，只提供了RandomLoadBalancer、NacosLoadBalancer、RoundRobinLoadBalancer，在不指定的时候默认使用RoundRobinLoadBalancer轮询负载均衡策略，此三种策略都是对接口ReactiveLoadBalancer 进行实现。

在这里插入图片描述

RandomLoadBalancer ：基于随机访问的负载均衡策略
NacosLoadBalancer：基于Nacos权重的负载均衡策略
RoundRobinLoadBalancer：基于轮询的负载均衡策略

三、切换LoadBalancer负载均衡策略

参考：
https://docs.spring.io/spring-cloud-commons/docs/current/reference/html/#rest-template-loadbalancer-client

https://docs.spring.io/spring-cloud-commons/docs/current/reference/html/#custom-loadbalancer-configuration

import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClients;
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.context.annotation.Configuration;
import org.springframework.core.env.Environment;

@Configuration
@LoadBalancerClients(defaultConfiguration = CustomRandomLoadBalancerConfiguration.class)
public class CustomRandomLoadBalancerConfiguration {

    @Bean
    ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,
                                                            LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new RandomLoadBalancer(loadBalancerClientFactory
                .getLazyProvider(name, ServiceInstanceListSupplier.class),
                name);
    }
}