springCloud-LoadBalancer负载均衡微服务负载均衡器LoadBalancer

2020年前SpringCloud是采用Ribbon作为负载均衡实现，但是在2020后采用了LoadBalancer替代

LoadBalancer默认提供了两种负载均衡策略（只能通过配置类来修改负载均衡策略）

1.RandomLoadBalancer-随机分配策略
2.RoundRobinLoadBalancer-轮询分配策略(默认)

添加一个自定义的负载均衡策略CustomLoadBalancerConfiguration 配置类，可以直接复制官网

package com.test.order.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);
        return new RandomLoadBalancer(loadBalancerClientFactory
                .getLazyProvider(name, ServiceInstanceListSupplier.class),
                name);
    }
}

注意如果负载均衡策略配置类使用spring注解@ComponentScan或者@Configuration，就要注意如果被SpringBootApplication的ComponentScan扫描到(默认扫描SpringBootApplication目录下的全部包)，就会变成全局的负载均衡策略，如果需要局部负载均衡最好不用注解，或者设置不被默认的ComponentScan扫描到

在启动类配置那个微服务使用那种负载均衡策略（如果有Ribbon负载均衡需要在yml负载均衡去掉，一般在2020版本后无需配置去掉，因为默认没有Ribbon）

@SpringBootApplication
//@LoadBalancerClients(defaultConfiguration={CustomLoadBalancerConfiguration.class})
//value的值表示需要负载均衡的微服务，调用指定的负载均衡策略
//@LoadBalancerClient(value = "stock-nacos",configuration = {CustomLoadBalancerConfiguration.class})
//@LoadBalancerClients({@LoadBalancerClient(value = "stock-nacos", configuration = {CustomLoadBalancerConfiguration.class}),@LoadBalancerClient(value = "stock-nacos2", configuration = {CustomLoadBalancerConfiguration2.class})})
@LoadBalancerClients({@LoadBalancerClient(value = "stock-nacos", configuration = {CustomLoadBalancerConfiguration.class})})
public class OrderLoadbalancerApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderLoadbalancerApplication.class, args);
    }

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(RestTemplateBuilder builder) {
        RestTemplate restTemplate = builder.build();
        return restTemplate;
    }
}

pom.xml配置(因为spring-cloud-starter-alibaba-nacos-discovery依赖中的spring-cloud-starter-loadbalancer的true，所以不会继承，需要收到继承)，如下

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
    </dependencies>

父pom.xml配置

    <dependencyManagement>
        <!--Spring Cloud alibaba的版本管理，通过dependency完成继承-->
        <dependencies>
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>2021.0.4.0</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>2021.0.4</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

遇到问题，点击spring-cloud-dependencies进不去查看pom文件，就是下载的pom有问题，可以都删除掉org.springframework.cloud目录下的文件，再重新刷新下载

版本链接对应