Spring Cloud ReactorServiceInstanceLoadBalancer 自定义负载均衡

自定义负载均衡类

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.*;
import org.springframework.cloud.loadbalancer.core.NoopServiceInstanceListSupplier;
import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
import org.springframework.cloud.loadbalancer.core.SelectedInstanceCallback;
import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
import org.springframework.http.HttpHeaders;
import reactor.core.publisher.Mono;

import java.util.List;

/**
 * 参照 org.springframework.cloud.loadbalancer.core.RandomLoadBalancer RoundRobinLoadBalancer
 *
 * @author 向振华
 * @date 2025/03/28 15:54
 */
public class MyLoadBalancer implements ReactorServiceInstanceLoadBalancer {
    private static final Log log = LogFactory.getLog(MyLoadBalancer.class);

    private final String serviceId;
    private ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;

    public MyLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider, String serviceId) {
        this.serviceId = serviceId;
        this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
    }

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

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

    private Response<ServiceInstance> getInstanceResponse(Request request, List<ServiceInstance> instances) {
        if (instances.isEmpty()) {
            log.error("No servers available for service: " + serviceId);
            return new EmptyResponse();
        } else {
            // 最终在这里选择服务
            // 这里自定义规则是根据请求头传的索引选择服务
            RequestDataContext context = (RequestDataContext) request.getContext();
            HttpHeaders headers = context.getClientRequest().getHeaders();
            String i = headers.getFirst("choose-index");
            ServiceInstance instance = instances.get(Integer.parseInt(i));
            return new DefaultResponse(instance);
        }
    }
}

配置类

import org.springframework.cloud.client.ServiceInstance;
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;

/**
 * @author 向振华
 * @date 2025/03/28 16:49
 */
public class MyLoadBalancerConfig {
    
    public MyLoadBalancerConfig() {
    }

    @Bean
    public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment, LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty("loadbalancer.client.name");
        return new MyLoadBalancer(loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
    }
}

然后在启动类加上注解，多个微服务在数组继续添加@LoadBalancerClient

@LoadBalancerClients({
        @LoadBalancerClient(name = "my-service", configuration = MyLoadBalancerConfig.class)
})

或者在引用的客户端类@FeignClient处，加@LoadBalancerClient

@LoadBalancerClient(name = "my-service",configuration = MyLoadBalancerConfig.class)