TreasuryYieldUpdateReducer.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.BasicDBObjectBuilder;
import com.mongodb.hadoop.io.MongoUpdateWritable;
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.io.NullWritable;
import org.apache.hadoop.mapreduce.Reducer;
import org.bson.BasicBSONObject;

import java.io.IOException;
import java.util.Date;

/**
 * The treasury yield reducer.
 */
public class TreasuryYieldUpdateReducer
    extends Reducer<IntWritable, DoubleWritable, NullWritable, MongoUpdateWritable> {

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

    public TreasuryYieldUpdateReducer() {
        super();
        reduceResult = new MongoUpdateWritable();
    }

    @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 query = new BasicBSONObject("_id", pKey.get());
        BasicBSONObject modifiers = new BasicBSONObject();
        modifiers.put("$set", BasicDBObjectBuilder.start()
                                                  .add("count", count)
                                                  .add("avg", avg)
                                                  .add("sum", sum)
                                                  .get());

        modifiers.put("$push", new BasicBSONObject("calculatedAt", new Date()));
        modifiers.put("$inc", new BasicBSONObject("numCalculations", 1));
        reduceResult.setQuery(query);
        reduceResult.setModifiers(modifiers);
        pContext.write(null, reduceResult);
    }

}