Fixed: server pulling old config in Nacos cluster mode (#3600)

* Fix nacos config update in Nacos cluster

* add capacity limit for nacos config snapshots

* add capacity limit for nacos config snapshots

* optimized the nacos config snapshot

spring-cloud-alibaba-starters/spring-cloud-starter-alibaba-nacos-config/src/main/java/com/alibaba/cloud/nacos/client/NacosPropertySourceBuilder.java

@@ -22,6 +22,7 @@ import java.util.List;
 
 import com.alibaba.cloud.nacos.NacosPropertySourceRepository;
 import com.alibaba.cloud.nacos.parser.NacosDataParserHandler;
+import com.alibaba.cloud.nacos.refresh.NacosSnapshotConfigManager;
 import com.alibaba.nacos.api.config.ConfigService;
 import com.alibaba.nacos.api.exception.NacosException;
 import org.slf4j.Logger;
@@ -82,7 +83,16 @@ public class NacosPropertySourceBuilder {
 			String fileExtension) {
 		String data = null;
 		try {
-			data = configService.getConfig(dataId, group, timeout);
+			String configSnapshot = NacosSnapshotConfigManager.getAndRemoveConfigSnapshot(dataId, group);
+			if (StringUtils.isEmpty(configSnapshot)) {
+				log.debug("get config from nacos, dataId: {}, group: {}", dataId, group);
+				data = configService.getConfig(dataId, group, timeout);
+			}
+			else {
+				log.debug("get config from memory snapshot, dataId: {}, group: {}",
+						dataId, group);
+				data = configSnapshot;
+			}
 			if (StringUtils.isEmpty(data)) {
 				log.warn(
 						"Ignore the empty nacos configuration and get it based on dataId[{}] & group[{}]",

spring-cloud-alibaba-starters/spring-cloud-starter-alibaba-nacos-config/src/main/java/com/alibaba/cloud/nacos/refresh/NacosContextRefresher.java

@@ -129,6 +129,8 @@ public class NacosContextRefresher
 							String configInfo) {
 						refreshCountIncrement();
 						nacosRefreshHistory.addRefreshRecord(dataId, group, configInfo);
+						NacosSnapshotConfigManager.putConfigSnapshot(dataId, group,
+								configInfo);
 						applicationContext.publishEvent(
 								new RefreshEvent(this, null, "Refresh Nacos config"));
 						if (log.isDebugEnabled()) {

spring-cloud-alibaba-starters/spring-cloud-starter-alibaba-nacos-config/src/main/java/com/alibaba/cloud/nacos/refresh/NacosSnapshotConfigManager.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2013-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.alibaba.cloud.nacos.refresh;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * @author: ruansheng
+ * @date: 2024-01-22
+ */
+public final class NacosSnapshotConfigManager {
+
+	private NacosSnapshotConfigManager() {
+	}
+
+	private static final Logger log = LoggerFactory
+			.getLogger(NacosSnapshotConfigManager.class);
+
+	private static final Map<String, String> CONFIG_INFO_SNAPSHOT_MAP = new ConcurrentHashMap<>(
+			8);
+
+	private static final int MAX_SNAPSHOT_COUNT = 100;
+
+	private static String formatConfigSnapshotKey(String dataId, String group) {
+		return dataId + "@" + group;
+	}
+
+	public static String getAndRemoveConfigSnapshot(String dataId, String group) {
+		String configInfo = CONFIG_INFO_SNAPSHOT_MAP
+				.get(formatConfigSnapshotKey(dataId, group));
+		removeConfigSnapshot(dataId, group);
+		return configInfo;
+	}
+
+	public static void putConfigSnapshot(String dataId, String group, String configInfo) {
+		try {
+			// Theoretically, the capacity limit restriction will never be triggered.
+			// This portion of the code serves as an additional fault tolerance layer.
+			if (CONFIG_INFO_SNAPSHOT_MAP.size() > MAX_SNAPSHOT_COUNT) {
+				Iterator<Map.Entry<String, String>> iterator = CONFIG_INFO_SNAPSHOT_MAP
+						.entrySet().iterator();
+				iterator.next();
+				iterator.remove();
+			}
+			CONFIG_INFO_SNAPSHOT_MAP.put(formatConfigSnapshotKey(dataId, group),
+					configInfo);
+		}
+		catch (Exception e) {
+			log.warn("remove nacos config snapshot error", e);
+		}
+	}
+
+	public static void removeConfigSnapshot(String dataId, String group) {
+		CONFIG_INFO_SNAPSHOT_MAP.remove(formatConfigSnapshotKey(dataId, group));
+	}
+
+}