AlphaPartitioner.java

package org.archive.hadoop.mapreduce;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;

import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Partitioner;

public class AlphaPartitioner extends Partitioner<Text, Text> implements
		Configurable {
	// TODO: refactor
	private static final Charset UTF8 = Charset.forName("UTF-8");
	
	private static String CONFIG_SPLIT_PATH_NAME = "alphapartitioner.path";
	private String boundaries[] = new String[0];

	Configuration conf;

	@Override
	public int getPartition(Text key, Text value, int numPartitions) {
		String keyS = key.toString();
		int loc = Arrays.binarySearch(boundaries, keyS);
		if (loc < 0) {
			loc = (loc * -1) - 2;
			if (loc < 0) {
				loc = 0;
			}
		}
		return loc;
	}

	public Configuration getConf() {
		return conf;
	}

	public void setConf(Configuration conf) {
		this.conf = conf;
		String partitionPath = getPartitionPath(conf);
		String numReduceTasks = conf.get("mapred.reduce.tasks");
		System.err.println("AlphaPartitioner-reducers: " + numReduceTasks);
		System.err.println("AlphaPartitioner-partitionPath: " + partitionPath);
		try {
			URI uri = new URI(partitionPath);
			FileSystem fs = FileSystem.get(uri, conf);
			Path p = new Path(partitionPath);
			loadBoundaries(new BufferedReader(new InputStreamReader(fs.open(p))));
		} catch (IOException e) {
			// TODO: ugh. how to handle?
			e.printStackTrace();
		} catch (URISyntaxException e) {
			e.printStackTrace();
		}
	}

	/**
	 * @param conf
	 *            Configuration for the Job
	 * @param path
	 *            hdfs:// URI pointing to the split file
	 */
	public static void setPartitionPath(Configuration conf, String path) {
		conf.set(CONFIG_SPLIT_PATH_NAME, path);
	}

	/**
	 * @param conf
	 *            Configuration for the Job
	 * @return the hdfs:// URI for the split file configured for this job
	 */
	public static String getPartitionPath(Configuration conf) {
		return conf.get(CONFIG_SPLIT_PATH_NAME);
	}
	
	public static int countLinesInPath(Path path, Configuration conf) 
	throws IOException {
		FileSystem fs = path.getFileSystem(conf);
		FSDataInputStream is = fs.open(path);
		BufferedReader br = new BufferedReader(new InputStreamReader(is, UTF8));
		int lineCount = 0;
		while (br.readLine() != null) {
			lineCount++;
		}
		is.close();
		return lineCount;
	}

	private void loadBoundaries(BufferedReader bis) throws IOException {
		ArrayList<String> l = new ArrayList<String>();
		while (true) {
			String line = bis.readLine();
			if (line == null) {
				break;
			}
			l.add(line);
		}
		boundaries = l.toArray(boundaries);
		Arrays.sort(boundaries);
	}
}