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 * Version in which HDFS-2991 was fixed. This bug caused OP_ADD to
049 * sometimes be skipped for append() calls. If we see such a case when
050 * loading the edits, but the version is known to have that bug, we
051 * workaround the issue. Otherwise we should consider it a corruption
052 * and bail.
053 */
054 public static final int BUGFIX_HDFS_2991_VERSION = -40;
055
056 /**
057 * Enums for features that change the layout version.
058 * <br><br>
059 * To add a new layout version:
060 * <ul>
061 * <li>Define a new enum constant with a short enum name, the new layout version
062 * and description of the added feature.</li>
063 * <li>When adding a layout version with an ancestor that is not same as
064 * its immediate predecessor, use the constructor where a spacific ancestor
065 * can be passed.
066 * </li>
067 * </ul>
068 */
069 public static enum Feature {
070 NAMESPACE_QUOTA(-16, "Support for namespace quotas"),
071 FILE_ACCESS_TIME(-17, "Support for access time on files"),
072 DISKSPACE_QUOTA(-18, "Support for disk space quotas"),
073 STICKY_BIT(-19, "Support for sticky bits"),
074 APPEND_RBW_DIR(-20, "Datanode has \"rbw\" subdirectory for append"),
075 ATOMIC_RENAME(-21, "Support for atomic rename"),
076 CONCAT(-22, "Support for concat operation"),
077 SYMLINKS(-23, "Support for symbolic links"),
078 DELEGATION_TOKEN(-24, "Support for delegation tokens for security"),
079 FSIMAGE_COMPRESSION(-25, "Support for fsimage compression"),
080 FSIMAGE_CHECKSUM(-26, "Support checksum for fsimage"),
081 REMOVE_REL13_DISK_LAYOUT_SUPPORT(-27, "Remove support for 0.13 disk layout"),
082 EDITS_CHESKUM(-28, "Support checksum for editlog"),
083 UNUSED(-29, "Skipped version"),
084 FSIMAGE_NAME_OPTIMIZATION(-30, "Store only last part of path in fsimage"),
085 RESERVED_REL20_203(-31, -19, "Reserved for release 0.20.203"),
086 RESERVED_REL20_204(-32, "Reserved for release 0.20.204"),
087 RESERVED_REL22(-33, -27, "Reserved for release 0.22"),
088 RESERVED_REL23(-34, -30, "Reserved for release 0.23"),
089 FEDERATION(-35, "Support for namenode federation"),
090 LEASE_REASSIGNMENT(-36, "Support for persisting lease holder reassignment"),
091 STORED_TXIDS(-37, "Transaction IDs are stored in edits log and image files"),
092 TXID_BASED_LAYOUT(-38, "File names in NN Storage are based on transaction IDs"),
093 EDITLOG_OP_OPTIMIZATION(-39,
094 "Use LongWritable and ShortWritable directly instead of ArrayWritable of UTF8");
095
096 final int lv;
097 final int ancestorLV;
098 final String description;
099
100 /**
101 * Feature that is added at {@code currentLV}.
102 * @param lv new layout version with the addition of this feature
103 * @param description description of the feature
104 */
105 Feature(final int lv, final String description) {
106 this(lv, lv + 1, description);
107 }
108
109 /**
110 * Feature that is added at {@code currentLV}.
111 * @param lv new layout version with the addition of this feature
112 * @param ancestorLV layout version from which the new lv is derived
113 * from.
114 * @param description description of the feature
115 */
116 Feature(final int lv, final int ancestorLV,
117 final String description) {
118 this.lv = lv;
119 this.ancestorLV = ancestorLV;
120 this.description = description;
121 }
122
123 /**
124 * Accessor method for feature layout version
125 * @return int lv value
126 */
127 public int getLayoutVersion() {
128 return lv;
129 }
130
131 /**
132 * Accessor method for feature ancestor layout version
133 * @return int ancestor LV value
134 */
135 public int getAncestorLayoutVersion() {
136 return ancestorLV;
137 }
138
139 /**
140 * Accessor method for feature description
141 * @return String feature description
142 */
143 public String getDescription() {
144 return description;
145 }
146 }
147
148 // Build layout version and corresponding feature matrix
149 static final Map<Integer, EnumSet<Feature>>map =
150 new HashMap<Integer, EnumSet<Feature>>();
151
152 // Static initialization
153 static {
154 initMap();
155 }
156
157 /**
158 * Initialize the map of a layout version and EnumSet of {@link Feature}s
159 * supported.
160 */
161 private static void initMap() {
162 // Go through all the enum constants and build a map of
163 // LayoutVersion <-> EnumSet of all supported features in that LayoutVersion
164 for (Feature f : Feature.values()) {
165 EnumSet<Feature> ancestorSet = map.get(f.ancestorLV);
166 if (ancestorSet == null) {
167 ancestorSet = EnumSet.noneOf(Feature.class); // Empty enum set
168 map.put(f.ancestorLV, ancestorSet);
169 }
170 EnumSet<Feature> featureSet = EnumSet.copyOf(ancestorSet);
171 featureSet.add(f);
172 map.put(f.lv, featureSet);
173 }
174
175 // Special initialization for 0.20.203 and 0.20.204
176 // to add Feature#DELEGATION_TOKEN
177 specialInit(Feature.RESERVED_REL20_203.lv, Feature.DELEGATION_TOKEN);
178 specialInit(Feature.RESERVED_REL20_204.lv, Feature.DELEGATION_TOKEN);
179 }
180
181 private static void specialInit(int lv, Feature f) {
182 EnumSet<Feature> set = map.get(lv);
183 set.add(f);
184 }
185
186 /**
187 * Gets formatted string that describes {@link LayoutVersion} information.
188 */
189 public static String getString() {
190 final StringBuilder buf = new StringBuilder();
191 buf.append("Feature List:\n");
192 for (Feature f : Feature.values()) {
193 buf.append(f).append(" introduced in layout version ")
194 .append(f.lv).append(" (").
195 append(f.description).append(")\n");
196 }
197
198 buf.append("\n\nLayoutVersion and supported features:\n");
199 for (Feature f : Feature.values()) {
200 buf.append(f.lv).append(": ").append(map.get(f.lv))
201 .append("\n");
202 }
203 return buf.toString();
204 }
205
206 /**
207 * Returns true if a given feature is supported in the given layout version
208 * @param f Feature
209 * @param lv LayoutVersion
210 * @return true if {@code f} is supported in layout version {@code lv}
211 */
212 public static boolean supports(final Feature f, final int lv) {
213 final EnumSet<Feature> set = map.get(lv);
214 return set != null && set.contains(f);
215 }
216
217 /**
218 * Get the current layout version
219 */
220 public static int getCurrentLayoutVersion() {
221 Feature[] values = Feature.values();
222 return values[values.length - 1].lv;
223 }
224 }