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：
-
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
-
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 {@Beanpublic 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);}@Overridepublic 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 {@Beanpublic 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: gatewaycloud:nacos:config:server-addr: 127.0.0.1:8848namespace: devgroup: DEFAULT_GROUPdiscovery:server-addr: 127.0.0.1:8848namespace: devgateway:routes:- id: order-serviceuri: lb://order-servicepredicates:- Path=/order/**filters:- StripPrefix=1
server:port: 90003.3 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）😂。
