com.neu.cs6240.TopKExperts.TopKPerHashTag.java Source code

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Here is the source code for com.neu.cs6240.TopKExperts.TopKPerHashTag.java

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/**
 *  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 com.neu.cs6240.TopKExperts;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

import au.com.bytecode.opencsv.CSVParser;

public class TopKPerHashTag {
    // Define Top K
    private static final int TOP_K = 5;
    // Column definition
    private static final int USER_ID = 0;
    private static final int ANS_COUNT = 1;
    private static final int HASH_TAG = 2;

    public static class TopKPerHashTagMapper extends Mapper<Object, Text, TopKPerHashTagKey, Text> {
        // initialize CSVParser as comma separated values
        private CSVParser csvParser = new CSVParser(',', '"');

        public void map(Object offset, Text line, Context context) throws IOException, InterruptedException {

            // Parse the input line
            String[] parsedData = null;
            try {
                parsedData = this.csvParser.parseLine(line.toString());
            } catch (Exception e) {
                // In case of bad data record ignore them
                return;
            }

            TopKPerHashTagKey key = null;
            int ansCountPerUserId;

            if (!isValid(parsedData)) {
                return;
            }

            // In case of invalid input continue
            try {
                ansCountPerUserId = Integer.parseInt(parsedData[ANS_COUNT]);
            } catch (NumberFormatException ex) {
                return;
            }

            key = new TopKPerHashTagKey(parsedData[HASH_TAG], ansCountPerUserId);
            context.write(key, new Text(parsedData[USER_ID]));
        }

        /**
         * remove invalid entries
         * 
         * @param parsedData
         * @return
         */
        private boolean isValid(String[] parsedData) {
            // We must have User ID, count per HashTag and HashTag
            if (parsedData[USER_ID].isEmpty() || parsedData[ANS_COUNT].isEmpty()
                    || parsedData[HASH_TAG].isEmpty()) {
                return false;
            }
            return true;
        }

    }

    public static class TopKPerHashTagReducer extends Reducer<TopKPerHashTagKey, Text, Text, Text> {

        public void reduce(TopKPerHashTagKey key, Iterable<Text> values, Context context)
                throws IOException, InterruptedException {

            StringBuilder kExperts = new StringBuilder();
            int findMore = TOP_K;

            for (Text value : values) {
                if (findMore <= 0) {
                    break;
                }

                if (kExperts.length() == 0) {
                    kExperts.append(value);
                    // Only for debug purpose
                    // kExperts.append(value).append("(" + key.getAnsCountPerUserId().get() +")");
                } else {
                    kExperts.append(",").append(value);
                    // Only for debug purpose
                    // kExperts.append(",").append(value).append("(" + key.getAnsCountPerUserId().get() +")");
                }
                findMore--;
            }

            // Output Top K Experts for this hash Tag         
            context.write(key.getHashTag(), new Text(kExperts.toString()));
        }
    }

    public static class TopKPerHashTagPartitioner extends Partitioner<TopKPerHashTagKey, Text> {
        /**
         * Based on the configured number of reducer, this will partition the
         * data approximately evenly based on number of unique HashTag
         */
        @Override
        public int getPartition(TopKPerHashTagKey key, Text value, int numPartitions) {
            // multiply by 127 to perform some mixing
            return Math.abs(key.getHashTag().hashCode() * 127) % numPartitions;
        }
    }

    public static class TopKPerHashTagGroupComparator extends WritableComparator {
        protected TopKPerHashTagGroupComparator() {
            super(TopKPerHashTagKey.class, true);
        }

        /**
         * Make sure that there'll be single reduce call per hash tag
         */
        @Override
        public int compare(WritableComparable w1, WritableComparable w2) {
            TopKPerHashTagKey key1 = (TopKPerHashTagKey) w1;
            TopKPerHashTagKey key2 = (TopKPerHashTagKey) w2;
            return key1.getHashTag().compareTo(key2.getHashTag());
        }
    }

    public static void main(String[] args) throws Exception {
        System.exit(TopKPerHashTag.initTopKPerHashTag(args) ? 0 : 1);
    }

    public static boolean initTopKPerHashTag(String[] args) throws Exception {
        Configuration conf = new Configuration();
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length != 2) {
            System.err.println("Usage: TopKPerHashTag <in> <out>");
            System.exit(2);
        }
        Job job = new Job(conf, "TopKPerHashTag");
        job.setJarByClass(TopKPerHashTag.class);
        job.setMapperClass(TopKPerHashTagMapper.class);
        job.setReducerClass(TopKPerHashTagReducer.class);
        job.setOutputKeyClass(TopKPerHashTagKey.class);
        job.setOutputValueClass(Text.class);
        job.setPartitionerClass(TopKPerHashTagPartitioner.class);
        job.setGroupingComparatorClass(TopKPerHashTagGroupComparator.class);
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));

        return job.waitForCompletion(true);
    }
}