feat：Nacos的防抖——获取失败临时使用本地缓存的列表顶一下

Author: xiaoyumuxi

rpc-core/src/main/java/com/xiaoyu/rpc/core/registry/nacos/NacosServiceDiscovery.java

@@ -3,24 +3,33 @@
 import com.alibaba.nacos.api.exception.NacosException;
 import com.alibaba.nacos.api.naming.NamingService;
 import com.alibaba.nacos.api.naming.pojo.Instance;
-import lombok.extern.slf4j.Slf4j;
-import com.xiaoyu.rpc.core.registry.ServiceDiscovery;
-
-import java.net.InetSocketAddress;
-import com.xiaoyu.rpc.core.config.RpcConfig;
+import com.alibaba.nacos.api.naming.listener.EventListener;
+import com.alibaba.nacos.api.naming.listener.Event;
+import com.alibaba.nacos.api.naming.listener.NamingEvent;
 import com.xiaoyu.rpc.common.extension.ExtensionLoader;
+import com.xiaoyu.rpc.core.config.RpcConfig;
 import com.xiaoyu.rpc.core.loadbalancer.LoadBalancer;
-import java.net.InetSocketAddress;
-import java.util.List;
-
+import com.xiaoyu.rpc.core.registry.ServiceDiscovery;
+import lombok.extern.slf4j.Slf4j;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.net.InetSocketAddress;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Collectors;
+
 public class NacosServiceDiscovery implements ServiceDiscovery {
     private static final Logger log = LoggerFactory.getLogger(NacosServiceDiscovery.class);
 
     private final NamingService namingService;
     private final LoadBalancer loadBalancer;
+    // 本地缓存，用于容错和防抖
+    private static final java.util.Map<String, List<Instance>> serviceCache = new java.util.concurrent.ConcurrentHashMap<>();
+    // 已订阅的服务集合
+    private static final java.util.Set<String> subscribedServices = java.util.concurrent.ConcurrentHashMap.newKeySet();
 
     public NacosServiceDiscovery() {
         this.namingService = NacosUtils.getNacosNamingService();
@@ -31,9 +40,24 @@ public NacosServiceDiscovery() {
     @Override
     public InetSocketAddress lookupService(String serviceName) {
         try {
+            // 第一次查找时订阅服务变更
+            if (subscribedServices.add(serviceName)) {
+                subscribeService(serviceName);
+            }
+
+            // 1. 优先尝试从 Nacos 获取最新实例
             List<Instance> instances = namingService.getAllInstances(serviceName);
-            if (instances.size() == 0) {
-                log.error("未找到服务: {}", serviceName);
+
+            if (instances.isEmpty()) {
+                log.warn("Nacos 返回实例列表为空，尝试使用本地缓存: {}", serviceName);
+                instances = serviceCache.get(serviceName);
+            } else {
+                // 更新本地缓存
+                serviceCache.put(serviceName, instances);
+            }
+
+            if (instances == null || instances.isEmpty()) {
+                log.error("未找到服务且本地无缓存: {}", serviceName);
                 throw new RuntimeException("未找到服务: " + serviceName);
             }
 
@@ -47,13 +71,39 @@ public InetSocketAddress lookupService(String serviceName) {
             log.info("负载均衡选择服务地址: {}", targetAddress);
 
             String[] array = targetAddress.split(":");
-            String host = array[0];
-            int port = Integer.parseInt(array[1]);
+            return new InetSocketAddress(array[0], Integer.parseInt(array[1]));
 
-            return new InetSocketAddress(host, port);
         } catch (NacosException e) {
-            log.error("获取服务实例时发生错误:", e);
+            log.error("获取服务实例时发生网络异常，尝试回滚到本地缓存:", e);
+            List<Instance> cachedInstances = serviceCache.get(serviceName);
+            if (cachedInstances != null && !cachedInstances.isEmpty()) {
+                List<String> addressList = cachedInstances.stream()
+                        .map(instance -> instance.getIp() + ":" + instance.getPort())
+                        .collect(java.util.stream.Collectors.toList());
+                String targetAddress = loadBalancer.select(addressList);
+                String[] array = targetAddress.split(":");
+                return new InetSocketAddress(array[0], Integer.parseInt(array[1]));
+            }
+            throw new RuntimeException("服务发现失败且无缓存可用: " + serviceName, e);
         }
-        return null;
+    }
+
+    /**
+     * 订阅服务变更，实现本地缓存的实时更新
+     */
+    private void subscribeService(String serviceName) throws NacosException {
+        namingService.subscribe(serviceName, new EventListener() {
+            @Override
+            public void onEvent(Event event) {
+                if (event instanceof NamingEvent) {
+                    NamingEvent namingEvent = (NamingEvent) event;
+                    List<Instance> instances = namingEvent.getInstances();
+                    log.info("监听到服务变更，更新本地缓存: {} -> 实例数 {}", serviceName, instances.size());
+                    if (instances != null && !instances.isEmpty()) {
+                        serviceCache.put(serviceName, instances);
+                    }
+                }
+            }
+        });
     }
 }