SpringCloud负载均衡spring-cloud-starter-loadbalancer解读

import org.springframework.beans.factory.annotation.Autowired;  
import org.springframework.cloud.client.loadbalancer.LoadBalanced;  
import org.springframework.context.annotation.Bean;  
import org.springframework.stereotype.Service;  
import org.springframework.web.reactive.function.client.WebClient;  
  
@Service  
public class MyServiceClient {  
  
    @Autowired  
    private WebClient.Builder webClientBuilder;  
  
    @Bean  
    @LoadBalanced  
    public WebClient.Builder loadBalancedwebClientBuilder() {  
        return WebClient.builder();  
    }  
  
    public String getSomethingFromMyService() {  
        // 注意这里我们直接使用了 "my-service" 作为 URI，而不是具体的服务实例地址  
        return webChttp://www.chinasem.cnlientBuilder.build()  
                .get()  
                .uri("http://my-service/some-endpoint")  
                .retrieve()  
                .bodyToMono(String.class)  
                .block(); // 注意：block() 方法会阻塞当前线程，通常只在非反应式上下文中使用  
    }  
}

		<!-- SpringCloud Loadbalancer -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>

import org.springframework.cloud.client.ServiceInstance;  
import org.springframework.cloud.client.loadbalancer.DefaultRequest;  
import org.springframework.cloud.client.loadbalancer.ReactiveLoadBalancer;  
import org.springframework.cloud.client.loadbalancer.ReactiveLoadBajslancerFactory;  
import org.springframework.cloud.client.ServiceInstanceChooser;  
import org.springframework.context.annotation.Bean;  
import org.springframework.context.annotation.Configuration;  
import reactor.core.publisher.Mono;  
  
import Java.util.List;  
  
@Configuration  
public class CustomLoadBalancerConfig {  
  
    @Bean  
    public ReactiveLoadBalancer<ServiceInstance> customLoadBalancer(  
            ReactiveLoadBalancerFactory<ServiceInstance> factory,  
            ObjectProvider<List<ServiceInstance>> serviceInstances) {  
  
        return new ReactiveLoadBalancer<ServiceInstance>() {  
  
            @Override  
            public Mono<China编程;Response<ServiceInstance>> choose(Request request) {  
                // 这里是自定义的负载均衡算法实现  
                // 例如，我们可以简单地返回服务实例列表中的第一个实例  
                return Mono.justOrEmpty(serviceInstances.getIfAvailable())  
                        .flatMapMany(List::stream)  
                        .firstElement() // 或者可以实现自己的选择逻辑  
                        .map(Response::just);  
            }  
  
            // 其他必要的方法（如 recordStats, filter, etc.）可以根据需要进行实现  
        };  
    }  
  
    // 如果想要为特定的服务配置自定义的负载均衡器，  
    // 可以通过 ServiceId 来区分并返回不同的 ReactiveLoadBalancer 实例  
    // 例如，public ReactiveLoadBalancer<ServiceInstance> customLoadBalancerForServiceX(...) {...}  
}

import org.springframework.cloud.client.ServiceInstance;  
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;  
import org.springframework.web.bind.annotation.GetMapping;  
import org.springframework.web.bind.annotation.RestController;  
import org.springframework.web.reactive.function.client.WebClient;  
  
import reactor.core.publisher.Mono;  
  
@RestController  
public class MyController {  
  
    private final LoadBalancerClient loadBalancerClient;  
  
    public MyController(LoadBalancerClient loadBalancerClient) {  
        this.loadBalancerClient = loadBalancerClient;  
    }  
  
    @GetMapping("/call-service")  
    public Mono<String> callService() {  
        // 获取服务实例  
        ServiceInstance serviceInstance = loadBalancerClient.choose("my-service").block();  
  
        // 使用 WebClient 发起反应式请求  
        WebClient webClient = WebClient.builder()  
                .baseUrl(serviceInstance.getUri().toString())  
                .build();  
  
        return webClient.get()  
                .uri("/some-endpoint")  
                .retrieve()  
                .bodyToMono(String.class);  
    }  
}

<dependencies>  
   <!-- ... 其他依赖 ... -->  
   <dependency>  
       <groupId>org.springframework.cloud</groupId>  
       <artifactId>spring-cloud-starter-openfeign</artifactId>  
   </dependency>  
   <dependency>  
       <groupId>org.springframework.cloud</groupId>  
       <artifactId>spring-cloud-starter-loadbalancer</artifactId>  
   </dependency>  
   <!-- ... 其他依赖 ... -->  
</dependencies>

@FeignClient(name = "my-service")  
public interface MyServiceClient {  
   // 定义 HTTP 方法  
   @GetMapping("/some-endpoint")  
   Mono<String> getSomething();  
}

@Bean  
public WebClient.Builder webClientBuilder(LoadBalancerClient loadBalancerClient) {  
    return WebClient.builder()  
            .baseUrl("lb://my-service") // 使用 'lb://' 前缀启用负载均衡  
            .filter(new LoadBalancerExchangeFilterFunction(loadBalancerClient));  
}

@Autowired  
private WebClient.Builder webClientBuilder;  
  
public Mono<String> callService() {  
    WebClient webClient = webClientBuilder.build();  
    return webClient.get()  
            .uri("/some-endpoint")  
            .retrieve()  
            .bodyToMono(String.class);  
}