remove empty object dir

Author: HTHou

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/rescon/disk/TierManager.java

@@ -39,6 +39,7 @@
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.FileStore;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -174,6 +175,16 @@ public synchronized void initFolders() {
       } catch (DiskSpaceInsufficientException e) {
         logger.error("All disks of tier {} are full.", tierLevel, e);
       }
+      // try to remove empty objectDirs
+      for (String dir : objectDirs) {
+        File dirFile = FSFactoryProducer.getFSFactory().getFile(dir);
+        if (dirFile.isDirectory() && Objects.requireNonNull(dirFile.list()).length == 0) {
+          try {
+            Files.delete(dirFile.toPath());
+          } catch (IOException ignore) {
+          }
+        }
+      }
     }
 
     tierDiskTotalSpace = getTierDiskSpace(DiskSpaceType.TOTAL);

iotdb-core/datanode/src/main/java/org/apache/iotdb/db/utils/ObjectTypeUtils.java

@@ -55,6 +55,7 @@
 import java.nio.file.StandardOpenOption;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 import java.util.Optional;
 
 public class ObjectTypeUtils {
@@ -310,8 +311,18 @@ public static void deleteObjectPath(File file) {
         logger.error("Failed to remove object file {}", file.getAbsolutePath(), e);
       }
     }
-    if (file.getParentFile().exists()) {
+    deleteEmptyParentDir(file);
+  }
 
+  private static void deleteEmptyParentDir(File file) {
+    File dir = file.getParentFile();
+    if (dir.isDirectory() && Objects.requireNonNull(dir.list()).length == 0) {
+      try {
+        Files.deleteIfExists(dir.toPath());
+        deleteEmptyParentDir(dir);
+      } catch (IOException e) {
+        logger.error("Failed to remove empty object dir {}", dir.getAbsolutePath(), e);
+      }
     }
   }