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
019 package org.apache.hadoop.net;
020
021 import java.util.*;
022 import java.io.*;
023
024 import org.apache.commons.logging.Log;
025 import org.apache.commons.logging.LogFactory;
026 import org.apache.hadoop.util.Shell.ShellCommandExecutor;
027 import org.apache.hadoop.classification.InterfaceAudience;
028 import org.apache.hadoop.classification.InterfaceStability;
029 import org.apache.hadoop.conf.Configurable;
030 import org.apache.hadoop.conf.Configuration;
031 import org.apache.hadoop.fs.CommonConfigurationKeys;
032
033 /**
034 * This class implements the {@link DNSToSwitchMapping} interface using a
035 * script configured via the
036 * {@link CommonConfigurationKeys#NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY} option.
037 * <p/>
038 * It contains a static class <code>RawScriptBasedMapping</code> that performs
039 * the work: reading the configuration parameters, executing any defined
040 * script, handling errors and such like. The outer
041 * class extends {@link CachedDNSToSwitchMapping} to cache the delegated
042 * queries.
043 * <p/>
044 * This DNS mapper's {@link #isSingleSwitch()} predicate returns
045 * true if and only if a script is defined.
046 */
047 @InterfaceAudience.Public
048 @InterfaceStability.Evolving
049 public final class ScriptBasedMapping extends CachedDNSToSwitchMapping {
050
051 /**
052 * Minimum number of arguments: {@value}
053 */
054 static final int MIN_ALLOWABLE_ARGS = 1;
055
056 /**
057 * Default number of arguments: {@value}
058 */
059 static final int DEFAULT_ARG_COUNT =
060 CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_NUMBER_ARGS_DEFAULT;
061
062 /**
063 * key to the script filename {@value}
064 */
065 static final String SCRIPT_FILENAME_KEY =
066 CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY ;
067 /**
068 * key to the argument count that the script supports
069 */
070 static final String SCRIPT_ARG_COUNT_KEY =
071 CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_NUMBER_ARGS_KEY ;
072
073 /**
074 * Create an instance with the default configuration.
075 * </p>
076 * Calling {@link #setConf(Configuration)} will trigger a
077 * re-evaluation of the configuration settings and so be used to
078 * set up the mapping script.
079 *
080 */
081 public ScriptBasedMapping() {
082 super(new RawScriptBasedMapping());
083 }
084
085 /**
086 * Create an instance from the given configuration
087 * @param conf configuration
088 */
089 public ScriptBasedMapping(Configuration conf) {
090 this();
091 setConf(conf);
092 }
093
094 /**
095 * Get the cached mapping and convert it to its real type
096 * @return the inner raw script mapping.
097 */
098 private RawScriptBasedMapping getRawMapping() {
099 return (RawScriptBasedMapping)rawMapping;
100 }
101
102 @Override
103 public Configuration getConf() {
104 return getRawMapping().getConf();
105 }
106
107 /**
108 * {@inheritDoc}
109 * <p/>
110 * This will get called in the superclass constructor, so a check is needed
111 * to ensure that the raw mapping is defined before trying to relaying a null
112 * configuration.
113 * @param conf
114 */
115 @Override
116 public void setConf(Configuration conf) {
117 super.setConf(conf);
118 getRawMapping().setConf(conf);
119 }
120
121 /**
122 * This is the uncached script mapping that is fed into the cache managed
123 * by the superclass {@link CachedDNSToSwitchMapping}
124 */
125 private static final class RawScriptBasedMapping
126 extends AbstractDNSToSwitchMapping {
127 private String scriptName;
128 private int maxArgs; //max hostnames per call of the script
129 private static final Log LOG =
130 LogFactory.getLog(ScriptBasedMapping.class);
131
132 /**
133 * Set the configuration and extract the configuration parameters of interest
134 * @param conf the new configuration
135 */
136 @Override
137 public void setConf (Configuration conf) {
138 super.setConf(conf);
139 if (conf != null) {
140 scriptName = conf.get(SCRIPT_FILENAME_KEY);
141 maxArgs = conf.getInt(SCRIPT_ARG_COUNT_KEY, DEFAULT_ARG_COUNT);
142 } else {
143 scriptName = null;
144 maxArgs = 0;
145 }
146 }
147
148 /**
149 * Constructor. The mapping is not ready to use until
150 * {@link #setConf(Configuration)} has been called
151 */
152 public RawScriptBasedMapping() {}
153
154 @Override
155 public List<String> resolve(List<String> names) {
156 List<String> m = new ArrayList<String>(names.size());
157
158 if (names.isEmpty()) {
159 return m;
160 }
161
162 if (scriptName == null) {
163 for (String name : names) {
164 m.add(NetworkTopology.DEFAULT_RACK);
165 }
166 return m;
167 }
168
169 String output = runResolveCommand(names);
170 if (output != null) {
171 StringTokenizer allSwitchInfo = new StringTokenizer(output);
172 while (allSwitchInfo.hasMoreTokens()) {
173 String switchInfo = allSwitchInfo.nextToken();
174 m.add(switchInfo);
175 }
176
177 if (m.size() != names.size()) {
178 // invalid number of entries returned by the script
179 LOG.error("Script " + scriptName + " returned "
180 + Integer.toString(m.size()) + " values when "
181 + Integer.toString(names.size()) + " were expected.");
182 return null;
183 }
184 } else {
185 // an error occurred. return null to signify this.
186 // (exn was already logged in runResolveCommand)
187 return null;
188 }
189
190 return m;
191 }
192
193 /**
194 * Build and execute the resolution command. The command is
195 * executed in the directory specified by the system property
196 * "user.dir" if set; otherwise the current working directory is used
197 * @param args a list of arguments
198 * @return null if the number of arguments is out of range,
199 * or the output of the command.
200 */
201 private String runResolveCommand(List<String> args) {
202 int loopCount = 0;
203 if (args.size() == 0) {
204 return null;
205 }
206 StringBuilder allOutput = new StringBuilder();
207 int numProcessed = 0;
208 if (maxArgs < MIN_ALLOWABLE_ARGS) {
209 LOG.warn("Invalid value " + Integer.toString(maxArgs)
210 + " for " + SCRIPT_ARG_COUNT_KEY + "; must be >= "
211 + Integer.toString(MIN_ALLOWABLE_ARGS));
212 return null;
213 }
214
215 while (numProcessed != args.size()) {
216 int start = maxArgs * loopCount;
217 List<String> cmdList = new ArrayList<String>();
218 cmdList.add(scriptName);
219 for (numProcessed = start; numProcessed < (start + maxArgs) &&
220 numProcessed < args.size(); numProcessed++) {
221 cmdList.add(args.get(numProcessed));
222 }
223 File dir = null;
224 String userDir;
225 if ((userDir = System.getProperty("user.dir")) != null) {
226 dir = new File(userDir);
227 }
228 ShellCommandExecutor s = new ShellCommandExecutor(
229 cmdList.toArray(new String[cmdList.size()]), dir);
230 try {
231 s.execute();
232 allOutput.append(s.getOutput()).append(" ");
233 } catch (Exception e) {
234 LOG.warn("Exception: ", e);
235 return null;
236 }
237 loopCount++;
238 }
239 return allOutput.toString();
240 }
241
242 /**
243 * Declare that the mapper is single-switched if a script was not named
244 * in the configuration.
245 * @return true iff there is no script
246 */
247 @Override
248 public boolean isSingleSwitch() {
249 return scriptName == null;
250 }
251 }
252 }