feat:support config empty protection.

polaris-common/polaris-config/src/main/java/com/tencent/polaris/api/config/configuration/ConnectorConfig.java

@@ -33,4 +33,18 @@ public interface ConnectorConfig extends ServerConnectorConfig {
      * @return 连接器类型
      */
     String getConnectorType();
+
+    /**
+     * 是否开启推空保护
+     *
+     * @return 是否开启推空保护
+     */
+    Boolean isEmptyProtectionEnable();
+
+    /**
+     * 推空保护过期时间，单位毫秒
+     *
+     * @return 推空保护过期时间
+     */
+    Long getEmptyProtectionExpiredInterval();
 }

polaris-common/polaris-config/src/main/java/com/tencent/polaris/factory/config/configuration/ConnectorConfigImpl.java

@@ -61,6 +61,13 @@ public class ConnectorConfigImpl extends ServerConnectorConfigImpl implements Co
     @JsonProperty
     private Integer configFileGroupThreadNum = 10;
 
+    @JsonProperty
+    private Boolean emptyProtectionEnable = true;
+
+    @JsonProperty
+    @JsonDeserialize(using = TimeStrJsonDeserializer.class)
+    private Long emptyProtectionExpiredInterval = 7 * 24 * 3600 * 1000L;
+
     @Override
     public void verify() {
         ConfigUtils.validateString(connectorType, "configConnectorType");
@@ -91,6 +98,12 @@ public void setDefault(Object defaultObject) {
             if (connectorType == null) {
                 this.connectorType = connectorConfig.getConnectorType();
             }
+            if (emptyProtectionEnable == null) {
+                this.emptyProtectionEnable = connectorConfig.isEmptyProtectionEnable();
+            }
+            if (emptyProtectionExpiredInterval == null) {
+                this.emptyProtectionExpiredInterval = connectorConfig.getEmptyProtectionExpiredInterval();
+            }
         }
     }
 
@@ -159,4 +172,21 @@ public void setConfigFileGroupThreadNum(Integer configFileGroupThreadNum) {
         this.configFileGroupThreadNum = configFileGroupThreadNum;
     }
 
+    @Override
+    public Boolean isEmptyProtectionEnable() {
+        return emptyProtectionEnable;
+    }
+
+    public void setEmptyProtectionEnable(Boolean emptyProtectionEnable) {
+        this.emptyProtectionEnable = emptyProtectionEnable;
+    }
+
+    @Override
+    public Long getEmptyProtectionExpiredInterval() {
+        return emptyProtectionExpiredInterval;
+    }
+
+    public void setEmptyProtectionExpiredInterval(Long emptyProtectionExpiredInterval) {
+        this.emptyProtectionExpiredInterval = emptyProtectionExpiredInterval;
+    }
 }

polaris-configuration/polaris-configuration-client/src/main/java/com/tencent/polaris/configuration/client/internal/RemoteConfigFileRepo.java

@@ -17,6 +17,7 @@
 
 package com.tencent.polaris.configuration.client.internal;
 
+import com.tencent.polaris.annonation.JustForTest;
 import com.tencent.polaris.api.control.Destroyable;
 import com.tencent.polaris.api.exception.ServerCodes;
 import com.tencent.polaris.api.plugin.configuration.ConfigFile;
@@ -27,11 +28,11 @@
 import com.tencent.polaris.client.api.SDKContext;
 import com.tencent.polaris.client.util.NamedThreadFactory;
 import com.tencent.polaris.configuration.api.core.ConfigFileMetadata;
+import com.tencent.polaris.configuration.client.util.ConfigFileUtils;
 
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -47,6 +48,8 @@ public class RemoteConfigFileRepo extends AbstractConfigFileRepo {
 
     private static ScheduledExecutorService pullExecutorService;
 
+    private static Set<String> configFileInitSet = new HashSet<>();
+
     private final AtomicReference<ConfigFile> remoteConfigFile;
     //服务端通知的版本号，此版本号有可能落后于服务端
     private final AtomicLong notifiedVersion;
@@ -58,6 +61,17 @@ public class RemoteConfigFileRepo extends AbstractConfigFileRepo {
 
     private String token;
 
+    private final boolean emptyProtection;
+
+    private final long emptyProtectionExpiredInterval;
+
+    /**
+     * 淘汰线程
+     */
+    private final ScheduledExecutorService emptyProtectionExpireExecutor;
+
+    private ScheduledFuture<?> emptyProtectionExpireFuture;
+
     static {
         createPullExecutorService();
     }
@@ -80,6 +94,9 @@ public RemoteConfigFileRepo(SDKContext sdkContext,
         //获取远程调用插件实现类
         this.configFileConnector = connector;
         this.fallbackToLocalCache = sdkContext.getConfig().getConfigFile().getServerConnector().getFallbackToLocalCache();
+        this.emptyProtection = sdkContext.getConfig().getConfigFile().getServerConnector().isEmptyProtectionEnable();
+        this.emptyProtectionExpiredInterval = sdkContext.getConfig().getConfigFile().getServerConnector().getEmptyProtectionExpiredInterval();
+        this.emptyProtectionExpireExecutor = Executors.newSingleThreadScheduledExecutor(new NamedThreadFactory("polaris-config-empty-protection"));
         //注册 destroy hook
         registerRepoDestroyHook(sdkContext);
         //同步从远程仓库拉取一次
@@ -163,32 +180,51 @@ protected void doPull() {
                     } else {
                         shouldUpdateLocalCache = remoteConfigFile.get() == null || pulledConfigFile.getVersion() != remoteConfigFile.get().getVersion();
                     }
-                    if (shouldUpdateLocalCache) {
+                    // 构造更新回调动作
+                    Runnable runnable = () -> {
                         ConfigFile copiedConfigFile = deepCloneConfigFile(pulledConfigFile);
                         remoteConfigFile.set(copiedConfigFile);
                         //配置有更新，触发回调
                         fireChangeEvent(copiedConfigFile);
 
                         // update local file cache
                         this.configFilePersistHandler.asyncSaveConfigFile(pulledConfigFile);
+                    };
+                    if (shouldUpdateLocalCache && checkEmptyProtect(response)) {
+                        shouldUpdateLocalCache = false;
+                        fallbackIfNecessaryWhenStartingUp(pullConfigFileReq);
+                        submitEmptyProtectionExpireTask(runnable);
+                    }
+                    if (shouldUpdateLocalCache) {
+                        runnable.run();
+                        cancelEmptyProtectionExpireTask();
                     }
                     return;
                 }
 
                 //远端没有此配置文件
                 if (response.getCode() == ServerCodes.NOT_FOUND_RESOURCE) {
-                    LOGGER.warn("[Config] config file not found, please check whether config file released. {}",
-                            configFileMetadata);
-                    //delete local file cache
-                    this.configFilePersistHandler
-                            .asyncDeleteConfigFile(new ConfigFile(configFileMetadata.getNamespace(),
-                                    configFileMetadata.getFileGroup(), configFileMetadata.getFileName()));
-
-                    //删除配置文件
-                    if (remoteConfigFile.get() != null) {
-                        remoteConfigFile.set(null);
-                        //删除配置文件也需要触发通知
-                        fireChangeEvent(null);
+                    // 构造更新回调动作
+                    Runnable runnable = () -> {
+                        //delete local file cache
+                        this.configFilePersistHandler
+                                .asyncDeleteConfigFile(new ConfigFile(configFileMetadata.getNamespace(),
+                                        configFileMetadata.getFileGroup(), configFileMetadata.getFileName()));
+
+                        //删除配置文件
+                        if (remoteConfigFile.get() != null) {
+                            remoteConfigFile.set(null);
+                            //删除配置文件也需要触发通知
+                            fireChangeEvent(null);
+                        }
+                    };
+                    if (checkEmptyProtect(response)) {
+                        fallbackIfNecessaryWhenStartingUp(pullConfigFileReq);
+                        submitEmptyProtectionExpireTask(runnable);
+                    } else {
+                        LOGGER.warn("[Config] config file not found, please check whether config file released. {}",
+                                configFileMetadata);
+                        runnable.run();
                     }
                     return;
                 }
@@ -213,16 +249,39 @@ protected void doPull() {
     }
 
     private void fallbackIfNecessary(final int retryTimes, ConfigFile configFileReq) {
-        if (retryTimes >= PULL_CONFIG_RETRY_TIMES && fallbackToLocalCache) {
+        if (retryTimes >= PULL_CONFIG_RETRY_TIMES) {
+            LOGGER.info("[Config] failed to pull config file from remote.");
+            //重试次数超过上限，从本地缓存拉取
+            loadLocalCache(configFileReq);
+        }
+    }
+
+    private void fallbackIfNecessaryWhenStartingUp(ConfigFile configFileReq) {
+        String identifier = getIdentifier();
+        boolean initFlag = false;
+        if (configFileInitSet.contains(identifier)) {
+            initFlag = true;
+        } else {
+            configFileInitSet.add(identifier);
+        }
+        if (!initFlag) {
+            // 第一次启动的时候，如果拉取到空配置，则尝试从缓存中获取
+            LOGGER.info("[Config] load local cache because of empty config when starting up.");
+            loadLocalCache(configFileReq);
+        }
+    }
+
+    private void loadLocalCache(ConfigFile configFileReq) {
+        if (fallbackToLocalCache) {
             ConfigFile configFileRes = configFilePersistHandler.loadPersistedConfigFile(configFileReq);
             if (configFileRes != null) {
-                LOGGER.info("[Config] failed to pull config file from remote,fallback to local cache success.{}.", configFileRes);
+                LOGGER.info("[Config] load local cache success.{}.", configFileRes);
                 remoteConfigFile.set(configFileRes);
                 //配置有更新，触发回调
                 fireChangeEvent(configFileRes);
                 return;
             }
-            LOGGER.info("[Config] failed to pull config file from remote,fallback to local cache fail.{}.", configFileReq);
+            LOGGER.info("[Config] load local cache fail.{}.", configFileReq);
         }
     }
 
@@ -293,4 +352,39 @@ protected void doDestroy() {
     static void destroyPullExecutor() {
         ThreadPoolUtils.waitAndStopThreadPools(new ExecutorService[]{pullExecutorService});
     }
+
+    /**
+     * 若配置为空，则推空保护开启，则不刷新配置
+     *
+     * @param configFileResponse
+     * @return
+     */
+    private boolean checkEmptyProtect(ConfigFileResponse configFileResponse) {
+        if (emptyProtection && ConfigFileUtils.checkConfigContentEmpty(configFileResponse)) {
+            LOGGER.warn("Empty response from remote with {}, will not refresh config.", getIdentifier());
+            return true;
+        }
+        return false;
+    }
+
+    private void submitEmptyProtectionExpireTask(Runnable runnable) {
+        if (emptyProtectionExpireFuture == null || emptyProtectionExpireFuture.isCancelled() || emptyProtectionExpireFuture.isDone()) {
+            LOGGER.info("Empty protection expire task of {} submit.", getIdentifier());
+            emptyProtectionExpireFuture = emptyProtectionExpireExecutor.schedule(runnable, emptyProtectionExpiredInterval, TimeUnit.MILLISECONDS);
+        }
+    }
+
+    private void cancelEmptyProtectionExpireTask() {
+        if (emptyProtectionExpireFuture != null && !emptyProtectionExpireFuture.isCancelled() && !emptyProtectionExpireFuture.isDone()) {
+            emptyProtectionExpireFuture.cancel(true);
+            LOGGER.info("Empty protection expire task of {} cancel.", getIdentifier());
+        }
+    }
+
+    @JustForTest
+    String getIdentifier() {
+        return configFileMetadata.getNamespace() + "."
+                + configFileMetadata.getFileGroup() + "."
+                + configFileMetadata.getFileName();
+    }
 }

polaris-configuration/polaris-configuration-client/src/main/java/com/tencent/polaris/configuration/client/util/ConfigFileUtils.java

@@ -18,8 +18,13 @@
 package com.tencent.polaris.configuration.client.util;
 
 import com.google.common.collect.Maps;
+import com.tencent.polaris.api.exception.ServerCodes;
+import com.tencent.polaris.api.plugin.configuration.ConfigFile;
+import com.tencent.polaris.api.plugin.configuration.ConfigFileResponse;
 import com.tencent.polaris.api.utils.StringUtils;
 import com.tencent.polaris.configuration.api.core.ConfigFileMetadata;
+import com.tencent.polaris.logging.LoggerFactory;
+import org.slf4j.Logger;
 
 import java.util.Collections;
 import java.util.Map;
@@ -31,6 +36,8 @@
  */
 public class ConfigFileUtils {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(ConfigFileUtils.class);
+
     public static void checkConfigFileMetadata(ConfigFileMetadata configFileMetadata) {
         if (StringUtils.isBlank(configFileMetadata.getNamespace())) {
             throw new IllegalArgumentException("namespace cannot be empty.");
@@ -57,4 +64,25 @@ public static Set<String> stringPropertyNames(Properties properties) {
         }
         return map.keySet();
     }
+
+    public static boolean checkConfigContentEmpty(ConfigFileResponse configFileResponse) {
+        if (configFileResponse == null) {
+            LOGGER.debug("config file response is null.");
+            return true;
+        }
+        if (configFileResponse.getCode() == ServerCodes.NOT_FOUND_RESOURCE) {
+            LOGGER.debug("config file not found. maybe not exist or deleted.");
+            return true;
+        }
+        ConfigFile configFile = configFileResponse.getConfigFile();
+        if (configFile == null) {
+            LOGGER.debug("config file is null.");
+            return true;
+        }
+        if (StringUtils.isBlank(configFile.getContent())) {
+            LOGGER.debug("config file content is empty.");
+            return true;
+        }
+        return false;
+    }
 }