负载均衡
Spring Cloud 采用客户端负载均衡：Consumer 从注册中心拉取实例列表后在本地选择目标实例，无需额外的 LB 服务器。Spring Boot 3.x / Spring Cloud 2022+ 默认使用 Spring Cloud LoadBalancer，已替代停维护的 Ribbon。
Spring Cloud LoadBalancer
依赖
<!-- 已内嵌在 nacos/eureka starter 中，通常无需单独引入 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>@LoadBalanced RestTemplate
@Configuration
public class RestConfig {
@Bean
@LoadBalanced // 拦截请求，将服务名解析为真实地址
public RestTemplate restTemplate() {
return new RestTemplate();
}
}
@Service
public class OrderClient {
@Autowired
private RestTemplate restTemplate;
public Order getOrder(Long id) {
return restTemplate.getForObject(
"http://order-service/orders/{id}", Order.class, id);
}
}@LoadBalanced WebClient
@Bean
@LoadBalanced
public WebClient.Builder webClientBuilder() {
return WebClient.builder();
}
public Mono<Order> getOrder(Long id) {
return webClientBuilder.build()
.get()
.uri("http://order-service/orders/{id}", id)
.retrieve()
.bodyToMono(Order.class);
}内置策略
| 策略 | 类名 | 说明 |
|---|---|---|
| 轮询（默认） | RoundRobinLoadBalancer | 依次轮流选择实例 |
| 随机 | RandomLoadBalancer | 随机选择实例 |
切换为随机策略
@Configuration
@LoadBalancerClient(name = "order-service",
configuration = RandomLBConfig.class)
public class LoadBalancerConfig {}
// 注意：此类不能加 @Configuration，避免被全局扫描
public class RandomLBConfig {
@Bean
public ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(
Environment env,
LoadBalancerClientFactory factory) {
String name = env.getProperty(
LoadBalancerClientFactory.PROPERTY_NAME);
return new RandomLoadBalancer(
factory.getLazyProvider(name, ServiceInstanceListSupplier.class),
name);
}
}自定义策略
public class WeightedLoadBalancer
implements ReactorServiceInstanceLoadBalancer {
private final ObjectProvider<ServiceInstanceListSupplier> provider;
private final String serviceId;
@Override
public Mono<Response<ServiceInstance>> choose(Request request) {
return provider
.getIfAvailable(NoopServiceInstanceListSupplier::new)
.get(request)
.next()
.map(instances -> {
ServiceInstance chosen = weightedRandom(instances);
return new DefaultResponse(chosen);
});
}
}实例缓存配置
spring:
cloud:
loadbalancer:
cache:
enabled: true
ttl: 35s # 缓存 TTL，建议略大于注册中心推送延迟
capacity: 256Nacos 权重 + 集群优先路由
Nacos 的 NacosLoadBalancer 支持按实例权重加权随机，并优先选择与 Consumer 同集群的实例：
spring:
cloud:
nacos:
discovery:
cluster-name: SH # Consumer 所在集群名