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     */
018    package org.apache.hadoop.hdfs.server.datanode;
019    
020    import java.util.HashMap;
021    import java.util.Map;
022    import java.util.SortedSet;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.hdfs.protocol.LayoutVersion;
026    import org.apache.hadoop.hdfs.protocol.LayoutVersion.FeatureInfo;
027    import org.apache.hadoop.hdfs.protocol.LayoutVersion.LayoutFeature;
028    
029    @InterfaceAudience.Private
030    public 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       
070        private final FeatureInfo info;
071    
072        /**
073         * DataNodeFeature that is added at layout version {@code lv} - 1. 
074         * @param lv new layout version with the addition of this feature
075         * @param description description of the feature
076         */
077        Feature(final int lv, final String description) {
078          this(lv, lv + 1, description, false);
079        }
080    
081        /**
082         * DataNode feature that is added at layout version {@code ancestoryLV}.
083         * @param lv new layout version with the addition of this feature
084         * @param ancestorLV layout version from which the new lv is derived from.
085         * @param description description of the feature
086         * @param reserved true when this is a layout version reserved for previous
087         *        version
088         * @param features set of features that are to be enabled for this version
089         */
090        Feature(final int lv, final int ancestorLV, final String description,
091            boolean reserved, Feature... features) {
092          info = new FeatureInfo(lv, ancestorLV, description, reserved, features);
093        }
094        
095        @Override
096        public FeatureInfo getInfo() {
097          return info;
098        }
099      }
100    }