com.kylinolap.job.hadoop.invertedindex.RandomKeyDistributionMapper.java Source code

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Here is the source code for com.kylinolap.job.hadoop.invertedindex.RandomKeyDistributionMapper.java

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/*
 * Copyright 2013-2014 eBay Software Foundation
 *
 * 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.kylinolap.job.hadoop.invertedindex;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ReflectionUtils;

import com.kylinolap.common.mr.KylinMapper;
import com.kylinolap.common.util.RandomSampler;
import com.kylinolap.job.constant.BatchConstants;

/**
 * @author ysong1
 * 
 */
public class RandomKeyDistributionMapper<KEY extends Writable, VALUE>
        extends KylinMapper<KEY, VALUE, KEY, NullWritable> {

    private Configuration conf;
    private int sampleNumber;
    private List<KEY> allKeys;

    @Override
    protected void setup(Context context) throws IOException {
        super.publishConfiguration(context.getConfiguration());

        conf = context.getConfiguration();
        allKeys = new ArrayList<KEY>();
        sampleNumber = Integer.parseInt(conf.get(BatchConstants.MAPPER_SAMPLE_NUMBER));
    }

    @SuppressWarnings("unchecked")
    @Override
    public void map(KEY key, VALUE value, Context context) throws IOException, InterruptedException {
        KEY keyCopy = (KEY) ReflectionUtils.newInstance(key.getClass(), conf);
        ReflectionUtils.copy(conf, key, keyCopy);
        allKeys.add(keyCopy);
    }

    @Override
    protected void cleanup(Context context) throws IOException, InterruptedException {
        RandomSampler<KEY> sampler = new RandomSampler<KEY>();
        List<KEY> sampleResult = sampler.sample(allKeys, sampleNumber);
        for (KEY k : sampleResult) {
            context.write(k, NullWritable.get());
        }
    }

}