SpringCloud自界说loadbalancer实现标签路由
一、配景近来前端反应开发环境有时间调接口会很慢，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克制该问题，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替换了，
Ribbon可以通过实现IRlue接口实现，这里只先容高版本的实现方案。
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，只需要清除掉NacosDiscoveryClientConfiguration，再写一个自己的NacosDiscoveryClientConfiguration设置类即可。
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);
}
}启动类上需要清除默认的NacosDiscoveryClientConfiguration，不然启动会报bean重复注册的错误，或者设置添加spring.main.allow-bean-definition-overriding=true允许重复注册也行。
写一个测试接口，方便背面测试
/**
* @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，所以需要界说一个设置类TagLoadBalancerConfig，并通过@LoadBalancerClients注解添加默认设置，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文件添加网关路由设置
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: 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
https://img2024.cnblogs.com/blog/1167086/202502/1167086-20250214200126345-92449439.png
[*]然后用Postman请求网关http://localhost:9000/order/test
https://img2024.cnblogs.com/blog/1167086/202502/1167086-20250214200756094-720647598.png
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，再次请求相应报文如下：
{
"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，实在现方案也不难，只需要通过上下文通报+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，趁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）
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