diamondmapreduce.NLineRecordReader.java Source code

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Here is the source code for diamondmapreduce.NLineRecordReader.java

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/*
 * Copyright 2016 YU Jia
    
   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 diamondmapreduce;

/**
 *
 * @author yujia1986
 */
import java.io.IOException;
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.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.util.LineReader;

public class NLineRecordReader extends RecordReader<LongWritable, Text> {

    //    private final int NLINESTOPROCESS = 45000;
    private final int NLINESTOPROCESS = 10000;
    private LineReader in;
    private LongWritable key;
    private Text value = new Text();
    private long start = 0;
    private long end = 0;
    private long pos = 0;
    private int maxLineLength;

    @Override
    public void close() throws IOException {
        if (in != null) {
            in.close();
        }
    }

    @Override
    public LongWritable getCurrentKey() throws IOException, InterruptedException {
        return key;
    }

    @Override
    public Text getCurrentValue() throws IOException, InterruptedException {
        return value;
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        if (start == end) {
            return 0.0f;
        } else {
            return Math.min(1.0f, (pos - start) / (float) (end - start));
        }
    }

    @Override
    public void initialize(InputSplit genericSplit, TaskAttemptContext context)
            throws IOException, InterruptedException {
        FileSplit split = (FileSplit) genericSplit;

        final Path file = split.getPath();
        Configuration conf = context.getConfiguration();
        this.maxLineLength = conf.getInt("mapreduce.input.linerecordreader.line.maxlength", Integer.MAX_VALUE);
        FileSystem fs = file.getFileSystem(conf);
        start = split.getStart();
        end = start + split.getLength();
        boolean skipFirstLine = false;
        FSDataInputStream filein = fs.open(split.getPath());

        if (start != 0) {
            skipFirstLine = true;
            --start;
            filein.seek(start);
        }
        in = new LineReader(filein, conf);
        if (skipFirstLine) {
            start += in.readLine(new Text(), 0, (int) Math.min((long) Integer.MAX_VALUE, end - start));
        }
        this.pos = start;
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        if (key == null) {
            key = new LongWritable();
        }
        key.set(pos);
        if (value == null) {
            value = new Text();
        }
        value.clear();
        final Text endline = new Text("\n");
        int newSize = 0;
        for (int i = 0; i < NLINESTOPROCESS; i++) {
            Text v = new Text();
            while (pos < end) {
                newSize = in.readLine(v, maxLineLength,
                        Math.max((int) Math.min(Integer.MAX_VALUE, end - pos), maxLineLength));
                value.append(v.getBytes(), 0, v.getLength());
                value.append(endline.getBytes(), 0, endline.getLength());
                if (newSize == 0) {
                    break;
                }
                pos += newSize;
                if (newSize < maxLineLength) {
                    break;
                }
            }
        }
        if (newSize == 0) {
            key = null;
            value = null;
            return false;
        } else {
            return true;
        }
    }

}