TreasuryYieldReducer.java

/*
 * Copyright 2011 10gen Inc.
 *
 * 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.mongodb.hadoop.examples.treasury;

import com.mongodb.hadoop.io.BSONWritable;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapreduce.Reducer;
import org.bson.BasicBSONObject;

import java.io.IOException;
import java.util.Iterator;

/**
 * The treasury yield reducer.
 */
public class TreasuryYieldReducer
    extends Reducer<IntWritable, DoubleWritable, IntWritable, BSONWritable> 
    implements org.apache.hadoop.mapred.Reducer<IntWritable, DoubleWritable, IntWritable, BSONWritable> {

    private static final Log LOG = LogFactory.getLog(TreasuryYieldReducer.class);
    private BSONWritable reduceResult;

    public TreasuryYieldReducer() {
        super();
        reduceResult = new BSONWritable();
    }

    @Override
    public void reduce(final IntWritable pKey, final Iterable<DoubleWritable> pValues, final Context pContext)
        throws IOException, InterruptedException {

        int count = 0;
        double sum = 0;
        for (final DoubleWritable value : pValues) {
            sum += value.get();
            count++;
        }

        final double avg = sum / count;

        if (LOG.isDebugEnabled()) {
            LOG.debug("Average 10 Year Treasury for " + pKey.get() + " was " + avg);
        }

        BasicBSONObject output = new BasicBSONObject();
        output.put("count", count);
        output.put("avg", avg);
        output.put("sum", sum);
        reduceResult.setDoc(output);
        pContext.write(pKey, reduceResult);
    }

    @Override
    public void reduce(final IntWritable key, final Iterator<DoubleWritable> values,
                       final OutputCollector<IntWritable, BSONWritable> output,
                       final Reporter reporter) throws IOException {
        int count = 0;
        double sum = 0;
        while (values.hasNext()) {
            sum += values.next().get();
            count++;
        }

        final double avg = sum / count;

        if (LOG.isDebugEnabled()) {
            LOG.debug("Average 10 Year Treasury for " + key.get() + " was " + avg);
        }

        BasicBSONObject bsonObject = new BasicBSONObject();
        bsonObject.put("count", count);
        bsonObject.put("avg", avg);
        bsonObject.put("sum", sum);
        reduceResult.setDoc(bsonObject);
        output.collect(key, reduceResult);
    }

    @Override
    public void close() throws IOException {
    }

    @Override
    public void configure(final JobConf job) {
    }
}