HDDS-15155. Add ozone debug ldb drop-column-family subcommand

hadoop-hdds/docs/content/tools/debug/Ldb.md

@@ -35,6 +35,7 @@ Commands:
   list_column_families, ls  list all column families in db.
   value-schema              Schema of value in metadataTable
   checkpoint                Create checkpoint for specified db
+  drop-column-family        Drop a column family from the DB.
 ```
 
 ### list_column_families command
@@ -60,6 +61,17 @@ revokedCerts
 move
 ```
 
+### drop-column-family command
+
+`drop-column-family` command drops a column family from the db provided. The service that owns the DB should be stopped
+before running this command. The command prompts for confirmation by default; use `-y` or `--yes` to skip the prompt.
+
+```bash
+$ ozone debug ldb --db=/path/to/om.db drop-column-family --cf=snapshotInfoTable
+WARNING: Dropping a column family mutates RocksDB and can be unsafe if the DB is already open by an Ozone process. Ensure the service that owns this DB is stopped before running this command. Do you want to continue (y/N)? y
+Dropped column family snapshotInfoTable
+```
+
 ### scan command
 
 `scan` command parses a particular column family of a rocksdb provided and prints the records.

hadoop-ozone/cli-debug/src/main/java/org/apache/hadoop/ozone/debug/ldb/DropColumnFamily.java

@@ -0,0 +1,146 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *      http://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 org.apache.hadoop.ozone.debug.ldb;
+
+import static org.apache.hadoop.hdds.utils.db.DBStoreBuilder.DEFAULT_COLUMN_FAMILY_NAME;
+
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+import java.util.concurrent.Callable;
+import org.apache.hadoop.hdds.cli.AbstractSubcommand;
+import org.apache.hadoop.hdds.utils.IOUtils;
+import org.apache.hadoop.hdds.utils.db.RocksDatabase;
+import org.apache.hadoop.hdds.utils.db.managed.ManagedConfigOptions;
+import org.apache.hadoop.hdds.utils.db.managed.ManagedDBOptions;
+import org.apache.hadoop.hdds.utils.db.managed.ManagedRocksDB;
+import org.apache.hadoop.ozone.debug.RocksDBUtils;
+import org.rocksdb.ColumnFamilyDescriptor;
+import org.rocksdb.ColumnFamilyHandle;
+import org.rocksdb.RocksDBException;
+import picocli.CommandLine;
+
+/**
+ * Drop a column family from a RocksDB.
+ */
+@CommandLine.Command(
+    name = "drop-column-family",
+    description = "Drop a column family from the DB.")
+public class DropColumnFamily extends AbstractSubcommand
+    implements Callable<Void> {
+
+  private static final String WARNING_TO_STOP_SERVICE =
+      "WARNING: Dropping a column family mutates RocksDB and can be unsafe " +
+          "if the DB is already open by an Ozone process. Ensure the service " +
+          "that owns this DB is stopped before running this command. " +
+          "Do you want to continue (y/N)? ";
+
+  @CommandLine.ParentCommand
+  private RDBParser parent;
+
+  @CommandLine.Option(names = {"--column-family", "--cf"},
+      required = true,
+      description = "Column family name")
+  private String columnFamilyName;
+
+  @CommandLine.Option(names = {"-y", "--yes"},
+      description = "Continue without interactive user confirmation")
+  private boolean yes;
+
+  @Override
+  public Void call() throws Exception {
+    if (isDefaultColumnFamily(columnFamilyName)) {
+      throw new IllegalArgumentException(
+          "Default column family cannot be dropped.");
+    }
+    if (!columnFamilyExists()) {
+      throw new IllegalArgumentException(columnFamilyName
+          + " is not a column family in DB for the given path.");
+    }
+
+    confirm();
+
+    ManagedConfigOptions configOptions = new ManagedConfigOptions();
+    ManagedDBOptions dbOptions = new ManagedDBOptions();
+    List<ColumnFamilyHandle> cfHandleList = new ArrayList<>();
+    List<ColumnFamilyDescriptor> cfDescList = new ArrayList<>();
+
+    try (ManagedRocksDB db = ManagedRocksDB.openWithLatestOptions(
+        configOptions, dbOptions, parent.getDbPath(), cfDescList,
+        cfHandleList)) {
+      ColumnFamilyHandle columnFamilyHandle =
+          RocksDBUtils.getColumnFamilyHandle(columnFamilyName, cfHandleList);
+      if (columnFamilyHandle == null) {
+        throw new IllegalArgumentException(columnFamilyName
+            + " is not a column family in DB for the given path.");
+      }
+
+      db.get().dropColumnFamily(columnFamilyHandle);
+      out().println("Dropped column family " + columnFamilyName);
+    } catch (RocksDBException exception) {
+      String errorMessage = "Failed to drop column family " + columnFamilyName
+          + " from RocksDB for the given path: " + parent.getDbPath();
+      throw new IOException(errorMessage, exception);
+    } finally {
+      IOUtils.closeQuietly(cfHandleList);
+      closeDescriptors(cfDescList);
+      IOUtils.closeQuietly(configOptions, dbOptions);
+    }
+
+    return null;
+  }
+
+  private static boolean isDefaultColumnFamily(String name) {
+    return DEFAULT_COLUMN_FAMILY_NAME.equals(name);
+  }
+
+  private void confirm() {
+    if (yes) {
+      return;
+    }
+
+    err().print(WARNING_TO_STOP_SERVICE);
+    err().flush();
+    Scanner scanner = new Scanner(new InputStreamReader(
+        System.in, StandardCharsets.UTF_8));
+    String confirmation = scanner.hasNextLine()
+        ? scanner.nextLine().trim() : "";
+    if (!"y".equalsIgnoreCase(confirmation)) {
+      throw new IllegalStateException("Aborting command.");
+    }
+  }
+
+  private boolean columnFamilyExists() throws RocksDBException {
+    for (byte[] columnFamily : RocksDatabase.listColumnFamiliesEmptyOptions(
+        parent.getDbPath())) {
+      if (columnFamilyName.equals(new String(columnFamily,
+          StandardCharsets.UTF_8))) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private static void closeDescriptors(
+      List<ColumnFamilyDescriptor> descriptors) {
+    descriptors.forEach(descriptor -> descriptor.getOptions().close());
+  }
+}

hadoop-ozone/cli-debug/src/main/java/org/apache/hadoop/ozone/debug/ldb/RDBParser.java

@@ -31,6 +31,7 @@
             ListTables.class,
             ValueSchema.class,
             Checkpoint.class,
+            DropColumnFamily.class,
         },
         description = "Parse rocksdb file content")
 @MetaInfServices(DebugSubcommand.class)