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：
[*]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 { @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")@RestControllerpublic 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})@SpringBootApplicationpublic 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: 127.0.0.1:8848 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=1server: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）😂。
页:
[1]