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.hdfs.server.datanode;
019
020import java.util.HashMap;
021import java.util.Map;
022import java.util.SortedSet;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.hdfs.protocol.LayoutVersion;
026import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo;
027import org.apache.hadoop.hdfs.protocol.LayoutVersion.LayoutFeature;
028
029@InterfaceAudience.Private
030public class DataNodeLayoutVersion {  
031  /** Build layout version and corresponding feature matrix */
032  public final static Map<Integer, SortedSet<LayoutFeature>> FEATURES = 
033    new HashMap<Integer, SortedSet<LayoutFeature>>();
034  
035  public static final int CURRENT_LAYOUT_VERSION
036      = LayoutVersion.getCurrentLayoutVersion(Feature.values());
037
038  static{
039    LayoutVersion.updateMap(FEATURES, LayoutVersion.Feature.values());
040    LayoutVersion.updateMap(FEATURES, DataNodeLayoutVersion.Feature.values());
041  }
042  
043  public static SortedSet<LayoutFeature> getFeatures(int lv) {
044    return FEATURES.get(lv);
045  }
046
047  public static boolean supports(final LayoutFeature f, final int lv) {
048    return LayoutVersion.supports(FEATURES, f, lv);
049  }
050
051  /**
052   * Enums for features that change the layout version.
053   * <br><br>
054   * To add a new layout version:
055   * <ul>
056   * <li>Define a new enum constant with a short enum name, the new layout version 
057   * and description of the added feature.</li>
058   * <li>When adding a layout version with an ancestor that is not same as
059   * its immediate predecessor, use the constructor where a specific ancestor
060   * can be passed.
061   * </li>
062   * </ul>
063   */
064  public static enum Feature implements LayoutFeature {
065    FIRST_LAYOUT(-55, -53, "First datanode layout", false),
066    BLOCKID_BASED_LAYOUT(-56,
067        "The block ID of a finalized block uniquely determines its position " +
068        "in the directory structure"),
069    BLOCKID_BASED_LAYOUT_32_by_32(-57,
070        "Identical to the block id based layout (-56) except it uses a smaller"
071        + " directory structure (32x32)");
072   
073    private final FeatureInfo info;
074
075    /**
076     * DataNodeFeature that is added at layout version {@code lv} - 1. 
077     * @param lv new layout version with the addition of this feature
078     * @param description description of the feature
079     */
080    Feature(final int lv, final String description) {
081      this(lv, lv + 1, description, false);
082    }
083
084    /**
085     * DataNode feature that is added at layout version {@code ancestoryLV}.
086     * @param lv new layout version with the addition of this feature
087     * @param ancestorLV layout version from which the new lv is derived from.
088     * @param description description of the feature
089     * @param reserved true when this is a layout version reserved for previous
090     *        version
091     * @param features set of features that are to be enabled for this version
092     */
093    Feature(final int lv, final int ancestorLV, final String description,
094        boolean reserved, Feature... features) {
095      info = new FeatureInfo(lv, ancestorLV, description, reserved, features);
096    }
097    
098    @Override
099    public FeatureInfo getInfo() {
100      return info;
101    }
102  }
103}