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.mapred.lib.aggregate;
020
021 import java.io.IOException;
022 import java.util.ArrayList;
023
024 import org.apache.hadoop.classification.InterfaceAudience;
025 import org.apache.hadoop.classification.InterfaceStability;
026 import org.apache.hadoop.conf.Configuration;
027 import org.apache.hadoop.fs.Path;
028 import org.apache.hadoop.io.Text;
029 import org.apache.hadoop.mapred.FileInputFormat;
030 import org.apache.hadoop.mapred.FileOutputFormat;
031 import org.apache.hadoop.mapred.InputFormat;
032 import org.apache.hadoop.mapred.JobClient;
033 import org.apache.hadoop.mapred.JobConf;
034 import org.apache.hadoop.mapred.SequenceFileInputFormat;
035 import org.apache.hadoop.mapred.TextInputFormat;
036 import org.apache.hadoop.mapred.TextOutputFormat;
037 import org.apache.hadoop.mapred.jobcontrol.Job;
038 import org.apache.hadoop.mapred.jobcontrol.JobControl;
039 import org.apache.hadoop.util.GenericOptionsParser;
040
041 /**
042 * This is the main class for creating a map/reduce job using Aggregate
043 * framework. The Aggregate is a specialization of map/reduce framework,
044 * specilizing for performing various simple aggregations.
045 *
046 * Generally speaking, in order to implement an application using Map/Reduce
047 * model, the developer is to implement Map and Reduce functions (and possibly
048 * combine function). However, a lot of applications related to counting and
049 * statistics computing have very similar characteristics. Aggregate abstracts
050 * out the general patterns of these functions and implementing those patterns.
051 * In particular, the package provides generic mapper/redducer/combiner classes,
052 * and a set of built-in value aggregators, and a generic utility class that
053 * helps user create map/reduce jobs using the generic class. The built-in
054 * aggregators include:
055 *
056 * sum over numeric values count the number of distinct values compute the
057 * histogram of values compute the minimum, maximum, media,average, standard
058 * deviation of numeric values
059 *
060 * The developer using Aggregate will need only to provide a plugin class
061 * conforming to the following interface:
062 *
063 * public interface ValueAggregatorDescriptor { public ArrayList<Entry>
064 * generateKeyValPairs(Object key, Object value); public void
065 * configure(JobConfjob); }
066 *
067 * The package also provides a base class, ValueAggregatorBaseDescriptor,
068 * implementing the above interface. The user can extend the base class and
069 * implement generateKeyValPairs accordingly.
070 *
071 * The primary work of generateKeyValPairs is to emit one or more key/value
072 * pairs based on the input key/value pair. The key in an output key/value pair
073 * encode two pieces of information: aggregation type and aggregation id. The
074 * value will be aggregated onto the aggregation id according the aggregation
075 * type.
076 *
077 * This class offers a function to generate a map/reduce job using Aggregate
078 * framework. The function takes the following parameters: input directory spec
079 * input format (text or sequence file) output directory a file specifying the
080 * user plugin class
081 */
082 @InterfaceAudience.Public
083 @InterfaceStability.Stable
084 public class ValueAggregatorJob {
085
086 public static JobControl createValueAggregatorJobs(String args[]
087 , Class<? extends ValueAggregatorDescriptor>[] descriptors) throws IOException {
088
089 JobControl theControl = new JobControl("ValueAggregatorJobs");
090 ArrayList<Job> dependingJobs = new ArrayList<Job>();
091 JobConf aJobConf = createValueAggregatorJob(args);
092 if(descriptors != null)
093 setAggregatorDescriptors(aJobConf, descriptors);
094 Job aJob = new Job(aJobConf, dependingJobs);
095 theControl.addJob(aJob);
096 return theControl;
097 }
098
099 public static JobControl createValueAggregatorJobs(String args[]) throws IOException {
100 return createValueAggregatorJobs(args, null);
101 }
102
103 /**
104 * Create an Aggregate based map/reduce job.
105 *
106 * @param args the arguments used for job creation. Generic hadoop
107 * arguments are accepted.
108 * @return a JobConf object ready for submission.
109 *
110 * @throws IOException
111 * @see GenericOptionsParser
112 */
113 public static JobConf createValueAggregatorJob(String args[])
114 throws IOException {
115
116 Configuration conf = new Configuration();
117
118 GenericOptionsParser genericParser
119 = new GenericOptionsParser(conf, args);
120 args = genericParser.getRemainingArgs();
121
122 if (args.length < 2) {
123 System.out.println("usage: inputDirs outDir "
124 + "[numOfReducer [textinputformat|seq [specfile [jobName]]]]");
125 GenericOptionsParser.printGenericCommandUsage(System.out);
126 System.exit(1);
127 }
128 String inputDir = args[0];
129 String outputDir = args[1];
130 int numOfReducers = 1;
131 if (args.length > 2) {
132 numOfReducers = Integer.parseInt(args[2]);
133 }
134
135 Class<? extends InputFormat> theInputFormat =
136 TextInputFormat.class;
137 if (args.length > 3 &&
138 args[3].compareToIgnoreCase("textinputformat") == 0) {
139 theInputFormat = TextInputFormat.class;
140 } else {
141 theInputFormat = SequenceFileInputFormat.class;
142 }
143
144 Path specFile = null;
145
146 if (args.length > 4) {
147 specFile = new Path(args[4]);
148 }
149
150 String jobName = "";
151
152 if (args.length > 5) {
153 jobName = args[5];
154 }
155
156 JobConf theJob = new JobConf(conf);
157 if (specFile != null) {
158 theJob.addResource(specFile);
159 }
160 String userJarFile = theJob.get("user.jar.file");
161 if (userJarFile == null) {
162 theJob.setJarByClass(ValueAggregator.class);
163 } else {
164 theJob.setJar(userJarFile);
165 }
166 theJob.setJobName("ValueAggregatorJob: " + jobName);
167
168 FileInputFormat.addInputPaths(theJob, inputDir);
169
170 theJob.setInputFormat(theInputFormat);
171
172 theJob.setMapperClass(ValueAggregatorMapper.class);
173 FileOutputFormat.setOutputPath(theJob, new Path(outputDir));
174 theJob.setOutputFormat(TextOutputFormat.class);
175 theJob.setMapOutputKeyClass(Text.class);
176 theJob.setMapOutputValueClass(Text.class);
177 theJob.setOutputKeyClass(Text.class);
178 theJob.setOutputValueClass(Text.class);
179 theJob.setReducerClass(ValueAggregatorReducer.class);
180 theJob.setCombinerClass(ValueAggregatorCombiner.class);
181 theJob.setNumMapTasks(1);
182 theJob.setNumReduceTasks(numOfReducers);
183 return theJob;
184 }
185
186 public static JobConf createValueAggregatorJob(String args[]
187 , Class<? extends ValueAggregatorDescriptor>[] descriptors)
188 throws IOException {
189 JobConf job = createValueAggregatorJob(args);
190 setAggregatorDescriptors(job, descriptors);
191 return job;
192 }
193
194 public static void setAggregatorDescriptors(JobConf job
195 , Class<? extends ValueAggregatorDescriptor>[] descriptors) {
196 job.setInt("aggregator.descriptor.num", descriptors.length);
197 //specify the aggregator descriptors
198 for(int i=0; i< descriptors.length; i++) {
199 job.set("aggregator.descriptor." + i, "UserDefined," + descriptors[i].getName());
200 }
201 }
202
203 /**
204 * create and run an Aggregate based map/reduce job.
205 *
206 * @param args the arguments used for job creation
207 * @throws IOException
208 */
209 public static void main(String args[]) throws IOException {
210 JobConf job = ValueAggregatorJob.createValueAggregatorJob(args);
211 JobClient.runJob(job);
212 }
213 }