001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.fs;
019
020import org.apache.hadoop.classification.InterfaceAudience;
021import org.apache.hadoop.classification.InterfaceStability;
022import org.apache.hadoop.conf.Configuration;
023import org.apache.hadoop.conf.Configured;
024import org.apache.hadoop.util.ReflectionUtils;
025
026import java.io.IOException;
027
028/** 
029 * This interface is used for implementing different Trash policies.
030 * Provides factory method to create instances of the configured Trash policy.
031 */
032@InterfaceAudience.Public
033@InterfaceStability.Evolving
034public abstract class TrashPolicy extends Configured {
035  protected FileSystem fs; // the FileSystem
036  protected Path trash; // path to trash directory
037  protected long deletionInterval; // deletion interval for Emptier
038
039  /**
040   * Used to setup the trash policy. Must be implemented by all TrashPolicy
041   * implementations
042   * @param conf the configuration to be used
043   * @param fs the filesystem to be used
044   * @param home the home directory
045   */
046  public abstract void initialize(Configuration conf, FileSystem fs, Path home);
047
048  /**
049   * Returns whether the Trash Policy is enabled for this filesystem
050   */
051  public abstract boolean isEnabled();
052
053  /** 
054   * Move a file or directory to the current trash directory.
055   * @return false if the item is already in the trash or trash is disabled
056   */ 
057  public abstract boolean moveToTrash(Path path) throws IOException;
058
059  /** 
060   * Create a trash checkpoint. 
061   */
062  public abstract void createCheckpoint() throws IOException;
063
064  /** 
065   * Delete old trash checkpoint(s).
066   */
067  public abstract void deleteCheckpoint() throws IOException;
068
069  /**
070   * Get the current working directory of the Trash Policy
071   */
072  public abstract Path getCurrentTrashDir();
073
074  /** 
075   * Return a {@link Runnable} that periodically empties the trash of all
076   * users, intended to be run by the superuser.
077   */
078  public abstract Runnable getEmptier() throws IOException;
079
080  /**
081   * Get an instance of the configured TrashPolicy based on the value 
082   * of the configuration parameter fs.trash.classname.
083   *
084   * @param conf the configuration to be used
085   * @param fs the file system to be used
086   * @param home the home directory
087   * @return an instance of TrashPolicy
088   */
089  public static TrashPolicy getInstance(Configuration conf, FileSystem fs, Path home) {
090    Class<? extends TrashPolicy> trashClass = conf.getClass(
091        "fs.trash.classname", TrashPolicyDefault.class, TrashPolicy.class);
092    TrashPolicy trash = ReflectionUtils.newInstance(trashClass, conf);
093    trash.initialize(conf, fs, home); // initialize TrashPolicy
094    return trash;
095  }
096}