org.apache.hama.util.Files.java Source code

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Here is the source code for org.apache.hama.util.Files.java

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/**
 *  Copyright (c) 2012 Apurv Verma
 *  Permission is hereby granted, free of charge, to any person obtaining
 *  a copy of this software and associated documentation files (the
 *  "Software"), to deal in the Software without restriction, including
 *  without limitation the rights to use, copy, modify, merge, publish,
 *  distribute, sublicense, and/or sell copies of the Software, and to
 *  permit persons to whom the Software is furnished to do so, subject to
 *  the following conditions:
 *  
 *  The above copyright notice and this permission notice shall be
 *  included in all copies or substantial portions of the Software.
 *  
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 
 *  limitations under the License.
 */
package org.apache.hama.util;

import java.io.IOException;
import java.util.HashMap;
import java.util.PriorityQueue;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hama.util.ReflectionUtils;

public class Files {

    private final static Log LOG = LogFactory.getLog(Files.class);

    /**
     * Merges k sequence files each of size n using knlog(k) merge algorithm.
     * @param  inputPath :the input directory which contains sorted sequence
     *                    files, that have to be merged.
     * @param  fs        :the filesystem
     * @return           :the Path to the merged sequence file.
     */
    public static <KEY extends WritableComparable<? super KEY>, VALUE extends Writable> Path merge(FileSystem fs,
            Path inputPath, Class<KEY> keyClazz, Class<VALUE> valClazz) {
        Path outputPath = new Path(inputPath.toString() + "/sorted/sorted_file.seq");
        merge(fs, inputPath, outputPath, keyClazz, valClazz);
        return outputPath;
    }

    /**
     * Merges k sequence files each of size n using knlog(k) merge algorithm.
     * @param  inputPath :the input directory which contains sorted sequence
     *                    files, that have to be merged.
     * @param  fs        :the filesystem
     * @param outputPath :the path to the merged sorted sequence file.
     */
    public static <KEY extends WritableComparable<? super KEY>, VALUE extends Writable> void merge(FileSystem fs,
            Path inputPath, Path outputPath, Class<KEY> keyClazz, Class<VALUE> valClazz) {

        Configuration conf = fs.getConf();

        PriorityQueue<KVPair<KEY, VALUE>> pq = new PriorityQueue<KVPair<KEY, VALUE>>();

        //Map from KeyValuePair to the split number to which it belongs.
        HashMap<KVPair<KEY, VALUE>, Integer> keySplitMap = new HashMap<KVPair<KEY, VALUE>, Integer>();

        FileStatus[] files;
        SequenceFile.Writer writer = null;
        SequenceFile.Reader reader[] = null;
        try {
            files = fs.listStatus(inputPath);
            reader = new SequenceFile.Reader[files.length];

            for (int i = 0; i < files.length; i++) {
                if (files[i].getLen() > 0) {
                    reader[i] = new SequenceFile.Reader(fs, files[i].getPath(), conf);
                    KEY key = ReflectionUtils.newInstance(keyClazz, new Object[0]);
                    VALUE val = ReflectionUtils.newInstance(valClazz, new Object[0]);

                    reader[i].next(key, val);
                    KVPair<KEY, VALUE> kv = new KVPair<KEY, VALUE>(key, val);
                    pq.add(kv);
                    keySplitMap.put(kv, i);
                }
            }

            writer = SequenceFile.createWriter(fs, conf, outputPath, keyClazz, valClazz);

            while (!pq.isEmpty()) {
                KVPair<KEY, VALUE> smallestKey = pq.poll();
                writer.append(smallestKey.getKey(), smallestKey.getValue());
                Integer index = keySplitMap.get(smallestKey);
                keySplitMap.remove(smallestKey);

                KEY key = ReflectionUtils.newInstance(keyClazz, new Object[0]);
                VALUE val = ReflectionUtils.newInstance(valClazz, new Object[0]);

                if (reader[index].next(key, val)) {
                    KVPair<KEY, VALUE> kv = new KVPair<KEY, VALUE>(key, val);
                    pq.add(kv);
                    keySplitMap.put(kv, index);
                }
            }

        } catch (IOException e) {
            LOG.error("Couldn't get status, exiting ...", e);
            System.exit(-1);
        } finally {
            if (writer != null) {
                try {
                    writer.close();
                } catch (IOException e) {
                    LOG.error("Cannot close writer to sorted seq. file. Exiting ...", e);
                    System.exit(-1);
                }
            }
        }
    }
}