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.protocol;
019
020 import java.util.EnumSet;
021 import java.util.HashMap;
022 import java.util.Map;
023
024 import org.apache.hadoop.classification.InterfaceAudience;
025
026 /**
027 * This class tracks changes in the layout version of HDFS.
028 *
029 * Layout version is changed for following reasons:
030 * <ol>
031 * <li>The layout of how namenode or datanode stores information
032 * on disk changes.</li>
033 * <li>A new operation code is added to the editlog.</li>
034 * <li>Modification such as format of a record, content of a record
035 * in editlog or fsimage.</li>
036 * </ol>
037 * <br>
038 * <b>How to update layout version:<br></b>
039 * When a change requires new layout version, please add an entry into
040 * {@link Feature} with a short enum name, new layout version and description
041 * of the change. Please see {@link Feature} for further details.
042 * <br>
043 */
044 @InterfaceAudience.Private
045 public class LayoutVersion {
046
047 /**
048 * Enums for features that change the layout version.
049 * <br><br>
050 * To add a new layout version:
051 * <ul>
052 * <li>Define a new enum constant with a short enum name, the new layout version
053 * and description of the added feature.</li>
054 * <li>When adding a layout version with an ancestor that is not same as
055 * its immediate predecessor, use the constructor where a spacific ancestor
056 * can be passed.
057 * </li>
058 * </ul>
059 */
060 public static enum Feature {
061 NAMESPACE_QUOTA(-16, "Support for namespace quotas"),
062 FILE_ACCESS_TIME(-17, "Support for access time on files"),
063 DISKSPACE_QUOTA(-18, "Support for disk space quotas"),
064 STICKY_BIT(-19, "Support for sticky bits"),
065 APPEND_RBW_DIR(-20, "Datanode has \"rbw\" subdirectory for append"),
066 ATOMIC_RENAME(-21, "Support for atomic rename"),
067 CONCAT(-22, "Support for concat operation"),
068 SYMLINKS(-23, "Support for symbolic links"),
069 DELEGATION_TOKEN(-24, "Support for delegation tokens for security"),
070 FSIMAGE_COMPRESSION(-25, "Support for fsimage compression"),
071 FSIMAGE_CHECKSUM(-26, "Support checksum for fsimage"),
072 REMOVE_REL13_DISK_LAYOUT_SUPPORT(-27, "Remove support for 0.13 disk layout"),
073 EDITS_CHESKUM(-28, "Support checksum for editlog"),
074 UNUSED(-29, "Skipped version"),
075 FSIMAGE_NAME_OPTIMIZATION(-30, "Store only last part of path in fsimage"),
076 RESERVED_REL20_203(-31, -19, "Reserved for release 0.20.203"),
077 RESERVED_REL20_204(-32, "Reserved for release 0.20.204"),
078 RESERVED_REL22(-33, -27, "Reserved for release 0.22"),
079 RESERVED_REL23(-34, -30, "Reserved for release 0.23"),
080 FEDERATION(-35, "Support for namenode federation"),
081 LEASE_REASSIGNMENT(-36, "Support for persisting lease holder reassignment"),
082 STORED_TXIDS(-37, "Transaction IDs are stored in edits log and image files"),
083 TXID_BASED_LAYOUT(-38, "File names in NN Storage are based on transaction IDs"),
084 EDITLOG_OP_OPTIMIZATION(-39,
085 "Use LongWritable and ShortWritable directly instead of ArrayWritable of UTF8");
086
087 final int lv;
088 final int ancestorLV;
089 final String description;
090
091 /**
092 * Feature that is added at {@code currentLV}.
093 * @param lv new layout version with the addition of this feature
094 * @param description description of the feature
095 */
096 Feature(final int lv, final String description) {
097 this(lv, lv + 1, description);
098 }
099
100 /**
101 * Feature that is added at {@code currentLV}.
102 * @param lv new layout version with the addition of this feature
103 * @param ancestorLV layout version from which the new lv is derived
104 * from.
105 * @param description description of the feature
106 */
107 Feature(final int lv, final int ancestorLV,
108 final String description) {
109 this.lv = lv;
110 this.ancestorLV = ancestorLV;
111 this.description = description;
112 }
113
114 /**
115 * Accessor method for feature layout version
116 * @return int lv value
117 */
118 public int getLayoutVersion() {
119 return lv;
120 }
121
122 /**
123 * Accessor method for feature ancestor layout version
124 * @return int ancestor LV value
125 */
126 public int getAncestorLayoutVersion() {
127 return ancestorLV;
128 }
129
130 /**
131 * Accessor method for feature description
132 * @return String feature description
133 */
134 public String getDescription() {
135 return description;
136 }
137 }
138
139 // Build layout version and corresponding feature matrix
140 static final Map<Integer, EnumSet<Feature>>map =
141 new HashMap<Integer, EnumSet<Feature>>();
142
143 // Static initialization
144 static {
145 initMap();
146 }
147
148 /**
149 * Initialize the map of a layout version and EnumSet of {@link Feature}s
150 * supported.
151 */
152 private static void initMap() {
153 // Go through all the enum constants and build a map of
154 // LayoutVersion <-> EnumSet of all supported features in that LayoutVersion
155 for (Feature f : Feature.values()) {
156 EnumSet<Feature> ancestorSet = map.get(f.ancestorLV);
157 if (ancestorSet == null) {
158 ancestorSet = EnumSet.noneOf(Feature.class); // Empty enum set
159 map.put(f.ancestorLV, ancestorSet);
160 }
161 EnumSet<Feature> featureSet = EnumSet.copyOf(ancestorSet);
162 featureSet.add(f);
163 map.put(f.lv, featureSet);
164 }
165
166 // Special initialization for 0.20.203 and 0.20.204
167 // to add Feature#DELEGATION_TOKEN
168 specialInit(Feature.RESERVED_REL20_203.lv, Feature.DELEGATION_TOKEN);
169 specialInit(Feature.RESERVED_REL20_204.lv, Feature.DELEGATION_TOKEN);
170 }
171
172 private static void specialInit(int lv, Feature f) {
173 EnumSet<Feature> set = map.get(lv);
174 set.add(f);
175 }
176
177 /**
178 * Gets formatted string that describes {@link LayoutVersion} information.
179 */
180 public static String getString() {
181 final StringBuilder buf = new StringBuilder();
182 buf.append("Feature List:\n");
183 for (Feature f : Feature.values()) {
184 buf.append(f).append(" introduced in layout version ")
185 .append(f.lv).append(" (").
186 append(f.description).append(")\n");
187 }
188
189 buf.append("\n\nLayoutVersion and supported features:\n");
190 for (Feature f : Feature.values()) {
191 buf.append(f.lv).append(": ").append(map.get(f.lv))
192 .append("\n");
193 }
194 return buf.toString();
195 }
196
197 /**
198 * Returns true if a given feature is supported in the given layout version
199 * @param f Feature
200 * @param lv LayoutVersion
201 * @return true if {@code f} is supported in layout version {@code lv}
202 */
203 public static boolean supports(final Feature f, final int lv) {
204 final EnumSet<Feature> set = map.get(lv);
205 return set != null && set.contains(f);
206 }
207
208 /**
209 * Get the current layout version
210 */
211 public static int getCurrentLayoutVersion() {
212 Feature[] values = Feature.values();
213 return values[values.length - 1].lv;
214 }
215 }