Spring Cloud Gateway 灰度负载均衡

1. 创建自定义负载均衡拦截器

   public class GrayscaleLoadBalancerClientFilter extends LoadBalancerClientFilter {
   
       private static final String VERSION = "version";
       private final DiscoveryClient discoveryClient;
       private final AtomicInteger nextServerCyclicCounter;
   
       public GrayscaleLoadBalancerClientFilter(LoadBalancerClient loadBalancer, DiscoveryClient discoveryClient) {
           super(loadBalancer);
           this.discoveryClient = discoveryClient;
           this.nextServerCyclicCounter = new AtomicInteger(0);
       }
   
       @Override
       protected ServiceInstance choose(ServerWebExchange exchange) {
           URI uri = (URI) exchange.getAttributes().get(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR);
           List<ServiceInstance> list = discoveryClient.getInstances(uri.getHost());
           if (CollectionUtils.isEmpty(list)) {
               return null;
           }
           List<String> listHeaders = exchange.getRequest().getHeaders().get(VERSION);
           String version = CollectionUtils.isEmpty(listHeaders)
                   ? null : (StringUtils.isBlank(listHeaders.get(0)) ? null : listHeaders.get(0));
           if (Objects.nonNull(version)) {
               list = list.stream().
                       filter(serviceInstance -> version.equals(serviceInstance.getMetadata().get(VERSION)))
                       .collect(Collectors.toList());
               if (!CollectionUtils.isEmpty(list)) {
                   return list.get(this.incrementAndGetModulo(list.size()));
               }
           }
           list = list.stream().
                   filter(serviceInstance -> !serviceInstance.getMetadata().containsKey(VERSION))
                   .collect(Collectors.toList());
           return list.isEmpty() ? null : list.get(this.incrementAndGetModulo(list.size()));
       }
   
       private int incrementAndGetModulo(int modulo) {
           int current;
           int next;
           do {
               current = this.nextServerCyclicCounter.get();
               next = (current + 1) % modulo;
           } while(!this.nextServerCyclicCounter.compareAndSet(current, next));
   
           return next;
       }
   }

2. 注入自定义负载均衡拦截器

   @Bean
   @Profile("dev")
   public LoadBalancerClientFilter loadBalancerClientFilter(LoadBalancerClient client,
                                                           DiscoveryClient discoveryClient) {
       return new GrayscaleLoadBalancerClientFilter(client, discoveryClient);
   }

3. 配置服务元数据

   可以在bootstrap.yml 中配置，或者在注册中心中设置

   spring:
       cloud:
           nacos:
               discovery:
                   metadata: 
                       version: 1