Java tutorial
/* * Cloud9: A MapReduce Library for Hadoop * * Licensed under the Apache License, Version 2.0 (the "License"); you * may not use this file except in compliance with the License. You may * obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or * implied. See the License for the specific language governing * permissions and limitations under the License. */ package edu.umd.cloud9.webgraph; import java.io.IOException; import java.net.URI; import java.util.Collections; import java.util.Iterator; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.SequenceFile; import org.apache.hadoop.mapred.FileOutputFormat; import org.apache.hadoop.mapred.JobClient; import org.apache.hadoop.mapred.JobConf; import org.apache.hadoop.mapred.MapReduceBase; import org.apache.hadoop.mapred.Mapper; import org.apache.hadoop.mapred.OutputCollector; import org.apache.hadoop.mapred.Partitioner; import org.apache.hadoop.mapred.Reducer; import org.apache.hadoop.mapred.Reporter; import org.apache.hadoop.mapred.SequenceFileInputFormat; import org.apache.hadoop.mapred.SequenceFileOutputFormat; import org.apache.log4j.Logger; import edu.umd.cloud9.io.array.ArrayListWritable; import edu.umd.cloud9.io.pair.PairOfIntString; import edu.umd.cloud9.util.PowerTool; import edu.umd.cloud9.webgraph.data.AnchorText; import edu.umd.cloud9.webgraph.data.AnchorTextConstants; /** * * @author Nima Asadi * */ public class CollectHostnames extends PowerTool { private static final Logger sLogger = Logger.getLogger(CollectHostnames.class); public static class Map extends MapReduceBase implements Mapper<IntWritable, ArrayListWritable<AnchorText>, PairOfIntString, IntWritable> { private static final PairOfIntString keyWord = new PairOfIntString(); private static final IntWritable valueWord = new IntWritable(); private static String host; public void map(IntWritable key, ArrayListWritable<AnchorText> anchors, OutputCollector<PairOfIntString, IntWritable> output, Reporter reporter) throws IOException { for (AnchorText data : anchors) { if (data.isURL()) try { //extract the hostname for a given URL host = new URI(data.getText()).getHost(); } catch (Exception e) { return; } } for (AnchorText data : anchors) { if (!data.isExternalOutLink()) continue; valueWord.set(key.get()); for (int target : data) { keyWord.set(target, host); output.collect(keyWord, valueWord); } } } } protected static class Partition implements Partitioner<PairOfIntString, IntWritable> { public void configure(JobConf job) { } public int getPartition(PairOfIntString key, IntWritable value, int numReduceTasks) { return Math.abs(key.getLeftElement() % numReduceTasks); } } public static class Reduce extends MapReduceBase implements Reducer<PairOfIntString, IntWritable, IntWritable, ArrayListWritable<AnchorText>> { private static OutputCollector<IntWritable, ArrayListWritable<AnchorText>> outputCollector; private static final ArrayListWritable<AnchorText> arrayList = new ArrayListWritable<AnchorText>(); private static final IntWritable keyWord = new IntWritable(); private static boolean firstTime = true; private static int currentDocument, packet; public void reduce(PairOfIntString key, Iterator<IntWritable> values, OutputCollector<IntWritable, ArrayListWritable<AnchorText>> output, Reporter reporter) throws IOException { if (firstTime) { outputCollector = output; firstTime = false; arrayList.clear(); currentDocument = key.getLeftElement(); } else if (currentDocument != key.getLeftElement()) { Collections.sort(arrayList); keyWord.set(currentDocument); output.collect(keyWord, arrayList); currentDocument = key.getLeftElement(); arrayList.clear(); } arrayList.add(new AnchorText(AnchorTextConstants.Type.OTHER_TYPES.val, key.getRightElement())); int currentIndex = arrayList.size() - 1; while (values.hasNext()) { packet = values.next().get(); //break larger chunks of data to smaller packets - reduces the underlying HashMap costs if (arrayList.get(currentIndex).getSize() < AnchorTextConstants.MAXIMUM_SOURCES_PER_PACKET) { arrayList.get(currentIndex).addDocument(packet); } else { arrayList.add(new AnchorText(AnchorTextConstants.Type.OTHER_TYPES.val, key.getRightElement(), packet)); currentIndex = arrayList.size() - 1; } } } public void close() throws IOException { Collections.sort(arrayList); keyWord.set(currentDocument); outputCollector.collect(keyWord, arrayList); } } public static final String[] RequiredParameters = { "Cloud9.InputPath", "Cloud9.OutputPath", "Cloud9.Mappers", "Cloud9.Reducers" }; public String[] getRequiredParameters() { return RequiredParameters; } public CollectHostnames(Configuration conf) { super(conf); } public int runTool() throws Exception { JobConf conf = new JobConf(getConf(), CollectHostnames.class); FileSystem fs = FileSystem.get(conf); int numMappers = conf.getInt("Cloud9.Mappers", 1); int numReducers = conf.getInt("Cloud9.Reducers", 200); String inputPath = conf.get("Cloud9.InputPath"); String outputPath = conf.get("Cloud9.OutputPath"); conf.setJobName("CollectHostnames"); conf.set("mapred.child.java.opts", "-Xmx4096m"); conf.setInt("mapred.task.timeout", 60000000); conf.setNumMapTasks(numMappers); conf.setNumReduceTasks(numReducers); conf.setMapperClass(Map.class); conf.setPartitionerClass(Partition.class); conf.setReducerClass(Reduce.class); conf.setOutputKeyClass(IntWritable.class); conf.setOutputValueClass(ArrayListWritable.class); conf.setMapOutputKeyClass(PairOfIntString.class); conf.setMapOutputValueClass(IntWritable.class); conf.setInputFormat(SequenceFileInputFormat.class); conf.setOutputFormat(SequenceFileOutputFormat.class); SequenceFileOutputFormat.setCompressOutput(conf, true); SequenceFileOutputFormat.setOutputCompressionType(conf, SequenceFile.CompressionType.BLOCK); SequenceFileInputFormat.setInputPaths(conf, inputPath); FileOutputFormat.setOutputPath(conf, new Path(outputPath)); sLogger.info("PropagateHostname"); sLogger.info(" - input path: " + inputPath); sLogger.info(" - output path: " + outputPath); if (!fs.exists(new Path(outputPath))) { JobClient.runJob(conf); } else { sLogger.info(outputPath + " already exists! Skipping this step..."); } return 0; } }