Fix empty snapshot loading and region cleanup

integration-test/src/test/java/org/apache/iotdb/db/it/IoTDBMiscIT.java

@@ -55,46 +55,46 @@ public void testCompressionRatioFile() throws SQLException {
         Statement statement = connection.createStatement()) {
       statement.execute("insert into root.comprssion_ratio_file.d1(timestamp,s1) values(1,1.0)");
       statement.execute("flush");
-      // one global file and two data region file (including one AUDIT region)
+      // one global file and one data region file
       assertEquals(2, collectCompressionRatioFiles(nodeWrapper).size());
 
       statement.execute("drop database root.comprssion_ratio_file");
-      // one global file and system region file
+      // one global file
       // deleting a file may not be sensed by other processes instantly
       Awaitility.await()
           .atMost(10, TimeUnit.SECONDS)
           .pollDelay(100, TimeUnit.MILLISECONDS)
-          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 2);
+          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 1);
 
       statement.execute("insert into root.comprssion_ratio_file.d1(timestamp,s1) values(1,1.0)");
       statement.execute("flush");
-      assertEquals(3, collectCompressionRatioFiles(nodeWrapper).size());
+      assertEquals(2, collectCompressionRatioFiles(nodeWrapper).size());
 
       statement.execute("drop database root.comprssion_ratio_file");
       Awaitility.await()
           .atMost(10, TimeUnit.SECONDS)
           .pollDelay(100, TimeUnit.MILLISECONDS)
-          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 2);
+          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 1);
 
       statement.execute("insert into root.comprssion_ratio_file.d1(timestamp,s1) values(1,1.0)");
       statement.execute("flush");
-      assertEquals(3, collectCompressionRatioFiles(nodeWrapper).size());
+      assertEquals(2, collectCompressionRatioFiles(nodeWrapper).size());
 
       statement.execute("insert into root.comprssion_ratio_file_2.d1(timestamp,s1) values(1,1.0)");
       statement.execute("flush");
-      assertEquals(4, collectCompressionRatioFiles(nodeWrapper).size());
+      assertEquals(3, collectCompressionRatioFiles(nodeWrapper).size());
 
       statement.execute("drop database root.comprssion_ratio_file");
       Awaitility.await()
           .atMost(10, TimeUnit.SECONDS)
           .pollDelay(100, TimeUnit.MILLISECONDS)
-          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 3);
+          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 2);
 
       statement.execute("drop database root.comprssion_ratio_file_2");
       Awaitility.await()
           .atMost(10, TimeUnit.SECONDS)
           .pollDelay(100, TimeUnit.MILLISECONDS)
-          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 2);
+          .until(() -> collectCompressionRatioFiles(nodeWrapper).size() == 1);
     } finally {
       simpleEnv.cleanClusterEnvironment();
     }

iotdb-core/datanode/src/main/i18n/en/org/apache/iotdb/db/i18n/StorageEngineMessages.java

@@ -359,10 +359,26 @@ private StorageEngineMessages() {}
   // ======================== Snapshot ========================
 
   public static final String EXCEPTION_LOAD_SNAPSHOT = "Exception occurs while load snapshot from {}";
+  public static final String LOADING_SNAPSHOT_FOR = "Loading snapshot for {}-{}, source directory is {}";
+  public static final String EXCEPTION_LOADING_SNAPSHOT_FOR = "Exception occurs when loading snapshot for {}-{}";
   public static final String READING_SNAPSHOT_LOG_FILE = "Reading snapshot log file {}";
   public static final String REMOVE_ALL_DATA_FILES_IN_ORIGINAL_DIR = "Remove all data files in original data dir";
   public static final String FAILED_TO_REMOVE_ORIGIN_DATA_FILES = "Failed to remove origin data files";
   public static final String MOVING_SNAPSHOT_FILE_TO_DATA_DIRS = "Moving snapshot file to data dirs";
+  public static final String CANNOT_FIND_SNAPSHOT_DIRECTORY = "Cannot find snapshot directory %s";
+  public static final String NO_SEQ_OR_UNSEQ_FILES_IN_SNAPSHOT =
+      "No seq or unseq files in snapshot {}, skip creating file links";
+  public static final String EXCEPTION_DELETING_TIME_PARTITION_DIR =
+      "Exception occurs when deleting time partition directory for {}-{}";
+  public static final String CANNOT_CREATE_LINK_FALLBACK_COPY =
+      "Cannot create link from {} to {}, fallback to copy";
+  public static final String FAILED_TO_PROCESS_SNAPSHOT_FILE =
+      "Failed to process file {} in dir {}: {}";
+  public static final String FAILED_TO_PROCESS_SNAPSHOT_FILE_AFTER_RETRIES =
+      "Failed to process file after retries. Source: %s, Target suffix: %s";
+  public static final String SNAPSHOT_FILE_NUM_MISMATCH =
+      "The file num in log is %d, while file num in disk is %d";
+  public static final String SNAPSHOT_FILE_NOT_IN_LOG = "File %s is not in the log file list";
   public static final String NO_COMPRESSION_RATIO_FILE_IN_DIR = "No compression ratio file in dir {}";
   public static final String CANNOT_LOAD_COMPRESSION_RATIO = "Cannot load compression ratio from {}";
   public static final String LOADED_COMPRESSION_RATIO = "Loaded compression ratio from {}";

iotdb-core/datanode/src/main/i18n/zh/org/apache/iotdb/db/i18n/StorageEngineMessages.java

@@ -359,10 +359,26 @@ private StorageEngineMessages() {}
   // ======================== Snapshot ========================
 
   public static final String EXCEPTION_LOAD_SNAPSHOT = "从 {} 加载快照时发生异常";
+  public static final String LOADING_SNAPSHOT_FOR = "正在为 {}-{} 加载快照，源目录为 {}";
+  public static final String EXCEPTION_LOADING_SNAPSHOT_FOR = "为 {}-{} 加载快照时发生异常";
   public static final String READING_SNAPSHOT_LOG_FILE = "正在读取快照日志文件 {}";
   public static final String REMOVE_ALL_DATA_FILES_IN_ORIGINAL_DIR = "移除原始数据目录中的所有数据文件";
   public static final String FAILED_TO_REMOVE_ORIGIN_DATA_FILES = "移除原始数据文件失败";
   public static final String MOVING_SNAPSHOT_FILE_TO_DATA_DIRS = "正在将快照文件移动到数据目录";
+  public static final String CANNOT_FIND_SNAPSHOT_DIRECTORY = "找不到快照目录 %s";
+  public static final String NO_SEQ_OR_UNSEQ_FILES_IN_SNAPSHOT =
+      "快照 {} 中没有顺序或乱序文件，跳过创建文件链接";
+  public static final String EXCEPTION_DELETING_TIME_PARTITION_DIR =
+      "删除 {}-{} 的时间分区目录时发生异常";
+  public static final String CANNOT_CREATE_LINK_FALLBACK_COPY =
+      "无法创建从 {} 到 {} 的链接，回退为复制";
+  public static final String FAILED_TO_PROCESS_SNAPSHOT_FILE =
+      "处理文件 {} 失败，所在目录为 {}: {}";
+  public static final String FAILED_TO_PROCESS_SNAPSHOT_FILE_AFTER_RETRIES =
+      "重试后仍无法处理文件。源文件: %s，目标后缀: %s";
+  public static final String SNAPSHOT_FILE_NUM_MISMATCH =
+      "日志中的文件数为 %d，但磁盘中的文件数为 %d";
+  public static final String SNAPSHOT_FILE_NOT_IN_LOG = "文件 %s 不在日志文件列表中";
   public static final String NO_COMPRESSION_RATIO_FILE_IN_DIR = "目录 {} 中没有压缩率文件";
   public static final String CANNOT_LOAD_COMPRESSION_RATIO = "无法从 {} 加载压缩率";
   public static final String LOADED_COMPRESSION_RATIO = "已从 {} 加载压缩率";

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/DataRegion.java

@@ -2201,7 +2201,9 @@
         databaseName + "-" + dataRegionIdString,
         systemDir);
     int regionId = dataRegionId.getId();
-    TableDiskUsageIndex.getInstance().remove(databaseName, regionId);
+    if (isTableModel) {
+      TableDiskUsageIndex.getInstance().remove(databaseName, regionId);
+    }
     FileTimeIndexCacheRecorder.getInstance().removeFileTimeIndexCache(regionId);
     writeLock("deleteFolder");
     try {
@@ -2635,7 +2637,7 @@
           if (tsFileProcessor == null) {
             // tsFileProcessor == null means this tsfile is being closed, here we try to busy loop
             // until status in TsFileResource has been changed which is supposed to be the last step
             // of closing
             while (!tsFileResource.isClosed() && waitTimeInMs > 0) {
               TimeUnit.MILLISECONDS.sleep(5);
               waitTimeInMs -= 5;
@@ -3073,7 +3075,7 @@
     writeLock("delete");
     boolean hasReleasedLock = false;
     try {
       if (deleted) {
         return;
       }
       String tableName = modEntries.get(0).getTableName();
@@ -3486,7 +3488,7 @@
           long matchSize =
               devicesInFile.stream()
                   .filter(
                       device -> {
                         if (logger.isDebugEnabled()) {
                           logger.debug(
                               "device is {}, deviceTable is {}, tableDeletionEntry.getPredicate().matches(device) is {}",

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/snapshot/SnapshotLoader.java

@@ -99,10 +99,7 @@ private File getSnapshotLogFile() {
    */
   public DataRegion loadSnapshotForStateMachine() {
     LOGGER.info(
-        "Loading snapshot for {}-{}, source directory is {}",
-        storageGroupName,
-        dataRegionId,
-        snapshotPath);
+        StorageEngineMessages.LOADING_SNAPSHOT_FOR, storageGroupName, dataRegionId, snapshotPath);
 
     File snapshotLogFile = getSnapshotLogFile();
 
@@ -129,7 +126,7 @@ private DataRegion loadSnapshotWithoutLog() {
       return loadSnapshot();
     } catch (IOException | DiskSpaceInsufficientException e) {
       LOGGER.error(
-          "Exception occurs when loading snapshot for {}-{}", storageGroupName, dataRegionId, e);
+          StorageEngineMessages.EXCEPTION_LOADING_SNAPSHOT_FOR, storageGroupName, dataRegionId, e);
       return null;
     }
   }
@@ -240,7 +237,7 @@ private void deleteAllFilesInDataDirs() throws IOException {
       }
     } catch (IOException e) {
       LOGGER.error(
-          "Exception occurs when deleting time partition directory for {}-{}",
+          StorageEngineMessages.EXCEPTION_DELETING_TIME_PARTITION_DIR,
           storageGroupName,
           dataRegionId,
           e);
@@ -250,6 +247,11 @@ private void deleteAllFilesInDataDirs() throws IOException {
 
   private void createLinksFromSnapshotDirToDataDirWithoutLog(File sourceDir)
       throws IOException, DiskSpaceInsufficientException {
+    if (!sourceDir.exists()) {
+      throw new IOException(
+          String.format(
+              StorageEngineMessages.CANNOT_FIND_SNAPSHOT_DIRECTORY, sourceDir.getAbsolutePath()));
+    }
     File seqFileDir =
         new File(
             sourceDir,
@@ -267,10 +269,8 @@ private void createLinksFromSnapshotDirToDataDirWithoutLog(File sourceDir)
                 + File.separator
                 + dataRegionId);
     if (!seqFileDir.exists() && !unseqFileDir.exists()) {
-      throw new IOException(
-          String.format(
-              "Cannot find %s or %s",
-              seqFileDir.getAbsolutePath(), unseqFileDir.getAbsolutePath()));
+      LOGGER.warn(StorageEngineMessages.NO_SEQ_OR_UNSEQ_FILES_IN_SNAPSHOT, sourceDir);
+      return;
     }
     FolderManager folderManager =
         new FolderManager(
@@ -329,24 +329,29 @@ private File createLinksFromSnapshotToSourceDir(
       if (!targetFile.getParentFile().exists() && !targetFile.getParentFile().mkdirs()) {
         throw new IOException(
             String.format(
-                "Cannot create directory %s", targetFile.getParentFile().getAbsolutePath()));
+                StorageEngineMessages.FAILED_TO_CREATE_DIR,
+                targetFile.getParentFile().getAbsolutePath()));
       }
 
       try {
         Files.createLink(targetFile.toPath(), file.toPath());
-        LOGGER.debug("Created hard link from {} to {}", file, targetFile);
+        LOGGER.debug(StorageEngineMessages.CREATED_HARD_LINK, file, targetFile);
         fileTarget.put(fileKey, finalDir);
         return targetFile;
       } catch (IOException e) {
-        LOGGER.info("Cannot create link from {} to {}, fallback to copy", file, targetFile);
+        LOGGER.info(StorageEngineMessages.CANNOT_CREATE_LINK_FALLBACK_COPY, file, targetFile);
       }
 
       Files.copy(file.toPath(), targetFile.toPath());
       fileTarget.put(fileKey, finalDir);
       return targetFile;
     } catch (Exception e) {
       LOGGER.warn(
-          "Failed to process file {} in dir {}: {}", file.getName(), finalDir, e.getMessage(), e);
+          StorageEngineMessages.FAILED_TO_PROCESS_SNAPSHOT_FILE,
+          file.getName(),
+          finalDir,
+          e.getMessage(),
+          e);
       throw e;
     }
   }
@@ -381,8 +386,9 @@ private void createLinksFromSnapshotToSourceDir(
       } catch (Exception e) {
         throw new IOException(
             String.format(
-                "Failed to process file after retries. Source: %s, Target suffix: %s",
-                file.getAbsolutePath(), targetSuffix),
+                StorageEngineMessages.FAILED_TO_PROCESS_SNAPSHOT_FILE_AFTER_RETRIES,
+                file.getAbsolutePath(),
+                targetSuffix),
             e);
       }
     }
@@ -409,8 +415,7 @@ private void createLinksFromSnapshotDirToDataDirWithLog() throws IOException {
     }
     if (fileCnt != loggedFileNum) {
       throw new IOException(
-          String.format(
-              "The file num in log is %d, while file num in disk is %d", loggedFileNum, fileCnt));
+          String.format(StorageEngineMessages.SNAPSHOT_FILE_NUM_MISMATCH, loggedFileNum, fileCnt));
     }
   }
 
@@ -492,13 +497,14 @@ private void createLinksFromSourceToTarget(File targetDir, File[] files, Set<Str
       String infoStr = getFileInfoString(file);
       if (!fileInfoSet.contains(infoStr)) {
         throw new IOException(
-            String.format("File %s is not in the log file list", file.getAbsolutePath()));
+            String.format(StorageEngineMessages.SNAPSHOT_FILE_NOT_IN_LOG, file.getAbsolutePath()));
       }
       File targetFile = new File(targetDir, file.getName());
       if (!targetFile.getParentFile().exists() && !targetFile.getParentFile().mkdirs()) {
         throw new IOException(
             String.format(
-                "Cannot create directory %s", targetFile.getParentFile().getAbsolutePath()));
+                StorageEngineMessages.FAILED_TO_CREATE_DIR,
+                targetFile.getParentFile().getAbsolutePath()));
       }
       Files.createLink(targetFile.toPath(), file.toPath());
     }

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/utils/tableDiskUsageIndex/TableDiskUsageIndex.java

@@ -443,18 +443,25 @@ private RemoveRegionOperation(String database, int regionId) {
 
     @Override
     public void apply(TableDiskUsageIndex tableDiskUsageIndex) {
-      tableDiskUsageIndex.writerMap.computeIfPresent(
-          regionId,
-          (k, writer) -> {
-            if (writer.getActiveReaderNum() > 0) {
-              // If there are active readers, defer removal until all readers finish
-              writer.setRemovedFuture(future);
-              return writer;
-            }
-            writer.close();
-            future.complete(null);
-            return null;
-          });
+      DataRegionTableSizeIndexWriter removedWriter = null;
+      try {
+        removedWriter =
+            tableDiskUsageIndex.writerMap.computeIfPresent(
+                regionId,
+                (k, writer) -> {
+                  if (writer.getActiveReaderNum() > 0) {
+                    // If there are active readers, defer removal until all readers finish
+                    writer.setRemovedFuture(future);
+                    return writer;
+                  }
+                  writer.close();
+                  return null;
+                });
+      } finally {
+        if (removedWriter == null) {
+          future.complete(null);
+        }
+      }
     }
   }
 

iotdb-core/datanode/src/test/java/org/apache/iotdb/db/storageengine/dataregion/snapshot/IoTDBSnapshotTest.java

@@ -183,6 +183,32 @@ public void testCreateSnapshotWithUnclosedTsFile()
     }
   }
 
+  @Test
+  public void testLoadEmptySnapshotWithoutLog() throws IOException {
+    String[][] originDataDirs = IoTDBDescriptor.getInstance().getConfig().getTierDataDirs();
+    IoTDBDescriptor.getInstance().getConfig().setTierDataDirs(testDataDirs);
+    TierManager.getInstance().resetFolders();
+    File snapshotDir = new File("target" + File.separator + "empty-snapshot");
+    try {
+      if (snapshotDir.exists()) {
+        FileUtils.recursivelyDeleteFolder(snapshotDir.getAbsolutePath());
+      }
+      Assert.assertTrue(snapshotDir.mkdirs());
+
+      DataRegion dataRegion =
+          new SnapshotLoader(snapshotDir.getAbsolutePath(), testSgName, "0")
+              .loadSnapshotForStateMachine();
+
+      Assert.assertNotNull(dataRegion);
+      assertEquals(0, dataRegion.getTsFileManager().getTsFileList(true).size());
+      assertEquals(0, dataRegion.getTsFileManager().getTsFileList(false).size());
+    } finally {
+      FileUtils.recursivelyDeleteFolder(snapshotDir.getAbsolutePath());
+      IoTDBDescriptor.getInstance().getConfig().setTierDataDirs(originDataDirs);
+      TierManager.getInstance().resetFolders();
+    }
+  }
+
   @Test
   public void testLoadSnapshot()
       throws IOException, WriteProcessException, DataRegionException, DirectoryNotLegalException {