SpringCloud自定义loadbalancer实现标签路由

一、背景

最近前端反应开发环境有时候调接口会很慢，原因是有开发图方便将本地服务注册到开发环境，请求路由到开发本地导致，

为了解决该问题想到可以通过标签路由的方式避免该问题，实现前端联调和开发自测互不干扰。

该方案除了用于本地调试，还可以用于用户灰度发布。

二、实现方案

关于负载均衡，低版本的SpringCloud用的是Spring Cloud Ribbon，高版本用Spring Cloud LoadBalancer替代了，

Ribbon可以通过实现IRlue接口实现，这里只介绍高版本的实现方案。

实现方案：

1. idea在环境变量中设置tag，本地服务启动时读取环境变量将tag注册到nacos的元数据

2. 重写网关的负载均衡算法，从请求头中获取到的request-tag和服务实例的元数据进行匹配，如果匹配到则返回对应的

   服务实例，否则提示服务未找到。

三、编码实现

3.1 order服务

新建一个SpringCloud服务order-service，注册元数据很简单，只需要排除掉NacosDiscoveryClientConfiguration，再写一个自己的NacosDiscoveryClientConfiguration配置类即可。

创建MyNacosDiscoveryClientConfiguration

/**
 * @Author: Ship
 * @Description:
 * @Date: Created in 2025/2/12
 */
@Configuration(
        proxyBeanMethods = false
)
@ConditionalOnDiscoveryEnabled
@ConditionalOnBlockingDiscoveryEnabled
@ConditionalOnNacosDiscoveryEnabled
@AutoConfigureBefore({SimpleDiscoveryClientAutoConfiguration.class, CommonsClientAutoConfiguration.class})
@AutoConfigureAfter({NacosDiscoveryAutoConfiguration.class})
public class MyNacosDiscoveryClientConfiguration {

    @Bean
    public DiscoveryClient nacosDiscoveryClient(NacosServiceDiscovery nacosServiceDiscovery) {
        return new NacosDiscoveryClient(nacosServiceDiscovery);
    }

    @Bean
    @ConditionalOnProperty(
            value = {"spring.cloud.nacos.discovery.watch.enabled"},
            matchIfMissing = true
    )
    public NacosWatch nacosWatch(NacosServiceManager nacosServiceManager, NacosDiscoveryProperties nacosDiscoveryProperties,
                                 ObjectProvider<ThreadPoolTaskScheduler> taskExecutorObjectProvider, Environment environment) {
        // 环境变量读取标签
        String tag = environment.getProperty("tag");
        nacosDiscoveryProperties.getMetadata().put("request-tag", tag);
        return new NacosWatch(nacosServiceManager, nacosDiscoveryProperties, taskExecutorObjectProvider);
    }
}

这里代码基本与NacosDiscoveryClientConfiguration一致，只是加上了设置元数据的逻辑。

@SpringBootApplication(exclude = NacosDiscoveryClientConfiguration.class)
public class OrderApplication {

    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }

}

启动类上需要排除默认的NacosDiscoveryClientConfiguration，不然启动会报bean重复注册的错误，或者配置添加spring.main.allow-bean-definition-overriding=true允许重复注册也行。

写一个测试接口，方便后面测试

/**
 * @Author: Ship
 * @Description:
 * @Date: Created in 2025/2/12
 */
@RequestMapping("test")
@RestController
public class TestController {

    @GetMapping("")
    public String sayHello(){
        return "hello";
    }
}

3.2 gateway服务

新建一个网关服务，pom文件如下：

 <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>2020.0.3</spring-cloud.version>
        <spring-cloud-alibaba.version>2021.1</spring-cloud-alibaba.version>
        <spring-boot.version>2.5.1</spring-boot.version>
        <maven-compiler-plugin.version>3.1</maven-compiler-plugin.version>
    </properties>
    <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>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <version>${spring-boot.version}</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <version>${spring-boot.version}</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
            <version>${spring-cloud-alibaba.version}</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            <version>${spring-cloud-alibaba.version}</version>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-bootstrap</artifactId>
            </dependency>
        </dependencies>

    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven-compiler-plugin.version}</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

Spring-Cloud-loadBalancer默认使用轮询的算法，即org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer类实现，因此可以参考RoundRobinLoadBalancer实现一个TagLoadBalancer，代码如下：

/**
 * @Author: Ship
 * @Description:
 * @Date: Created in 2025/2/12
 */
public class TagLoadBalancer implements ReactorServiceInstanceLoadBalancer {

    private static final String TAG_HEADER = "request-tag";

    private static final Log log = LogFactory.getLog(TagLoadBalancer.class);
    final AtomicInteger position;
    final String serviceId;
    ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;

    public TagLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider, String serviceId) {
        this(serviceInstanceListSupplierProvider, serviceId, (new Random()).nextInt(1000));
    }

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

    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        ServiceInstanceListSupplier supplier = (ServiceInstanceListSupplier) this.serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new);
        return supplier.get(request).next().map((serviceInstances) -> {
            return this.processInstanceResponse(supplier, serviceInstances, request);
        });
    }

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

        return serviceInstanceResponse;
    }

    private Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances, Request request) {
        if (instances.isEmpty()) {
            if (log.isWarnEnabled()) {
                log.warn("No servers available for service: " + this.serviceId);
            }
            return new EmptyResponse();
        }
        if (request instanceof DefaultRequest) {
            DefaultRequest<RequestDataContext> defaultRequest = (DefaultRequest) request;
            // 上下文获取请求头
            HttpHeaders headers = defaultRequest.getContext().getClientRequest().getHeaders();
            List<String> list = headers.get(TAG_HEADER);
            if (!CollectionUtils.isEmpty(list)) {
                String requestTag = list.get(0);
                for (ServiceInstance instance : instances) {
                    String str = instance.getMetadata().getOrDefault(TAG_HEADER, "");
                    if (requestTag.equals(str)) {
                        return new DefaultResponse(instance);
                    }
                }
                log.error(String.format("No servers available for service:%s,tag:%s ", this.serviceId, requestTag));
                return new EmptyResponse();
            }
        }

        int pos = Math.abs(this.position.incrementAndGet());
        ServiceInstance instance = instances.get(pos % instances.size());
        return new DefaultResponse(instance);
    }
}

这里需要实现ReactorServiceInstanceLoadBalancer接口，如果请求头带有标签则根据标签路由，否则使用默认的轮询算法。

还要把TagLoadBalancer用起来，所以需要定义一个配置类TagLoadBalancerConfig，并通过@LoadBalancerClients注解添加默认配置，代码如下：

/**
 * @Author: Ship
 * @Description:
 * @Date: Created in 2025/2/12
 */
public class TagLoadBalancerConfig {

    @Bean
    public ReactorLoadBalancer reactorTagLoadBalancer(Environment environment, LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new TagLoadBalancer(loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
    }
}

@LoadBalancerClients(defaultConfiguration = {TagLoadBalancerConfig.class})
@SpringBootApplication
public class GatewayApplication {

    public static void main(String[] args) {
        SpringApplication.run(GatewayApplication.class, args);
    }

}

最后在application.yml文件添加网关路由配置

spring:
  application:
    name: gateway
  cloud:
    nacos:
      config:
        server-addr: 127.0.0.1:8848
        namespace: dev
        group: DEFAULT_GROUP
      discovery:
        server-addr: 127.0.0.1:8848
        namespace: dev
    gateway:
      routes:
        - id: order-service
          uri: lb://order-service
          predicates:
            - Path=/order/**
          filters:
            - StripPrefix=1
server:
  port: 9000

3.3 代码测试

• 本地启动nacos后启动order（注意需要在idea设置环境变量tag=ship）和gateway服务，可以看到order服务已经成功注册了元数据

  

• 然后用Postman请求网关http://localhost:9000/order/test

可以看到请求成功路由到了order服务，说明根据tag路由成功了。

• 去掉环境变量tag后重新启动Order服务，再次请求响应报文如下：

  {
      "timestamp": "2025-02-14T12:10:44.294+00:00",
      "path": "/order/test",
      "status": 503,
      "error": "Service Unavailable",
      "requestId": "41651188-4"
  }
  

说明根据requst-tag找不到对应的服务实例，代码逻辑生效了。

四、总结

聪明的人已经发现了，本文只实现了网关路由到下游服务这部分的标签路由，下游服务A调服务B的标签路由并未实现，其实现方案也不难，只需要通过上下文传递+feign拦截器就可以做到全链路的标签路由，有兴趣的可以自己试试。

  本文代码已上传github，顺便推广下前段时间写的idea插件CodeFaster（快速生成常用流操作的代码，Marketplace搜索下载即可体验）。