[120] | 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 3 | * or more contributor license agreements. See the NOTICE file |
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| 4 | * distributed with this work for additional information |
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| 5 | * regarding copyright ownership. The ASF licenses this file |
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| 6 | * to you under the Apache License, Version 2.0 (the |
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| 7 | * "License"); you may not use this file except in compliance |
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| 8 | * with the License. You may obtain a copy of the License at |
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| 9 | * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 11 | * |
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| 12 | * Unless required by applicable law or agreed to in writing, software |
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| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 15 | * See the License for the specific language governing permissions and |
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| 16 | * limitations under the License. |
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| 17 | */ |
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| 18 | |
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| 19 | package org.apache.hadoop.mapreduce.lib.input; |
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| 20 | |
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| 21 | import java.io.IOException; |
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| 22 | |
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| 23 | import org.apache.hadoop.conf.Configuration; |
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| 24 | import org.apache.hadoop.fs.FSDataInputStream; |
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| 25 | import org.apache.hadoop.fs.FileSystem; |
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| 26 | import org.apache.hadoop.fs.Path; |
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| 27 | import org.apache.hadoop.io.LongWritable; |
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| 28 | import org.apache.hadoop.io.Text; |
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| 29 | import org.apache.hadoop.io.compress.CompressionCodec; |
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| 30 | import org.apache.hadoop.io.compress.CompressionCodecFactory; |
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| 31 | import org.apache.hadoop.mapreduce.InputSplit; |
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| 32 | import org.apache.hadoop.mapreduce.RecordReader; |
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| 33 | import org.apache.hadoop.mapreduce.TaskAttemptContext; |
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| 34 | import org.apache.hadoop.util.LineReader; |
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| 35 | import org.apache.commons.logging.LogFactory; |
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| 36 | import org.apache.commons.logging.Log; |
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| 37 | |
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| 38 | /** |
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| 39 | * Treats keys as offset in file and value as line. |
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| 40 | */ |
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| 41 | public class LineRecordReader extends RecordReader<LongWritable, Text> { |
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| 42 | private static final Log LOG = LogFactory.getLog(LineRecordReader.class); |
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| 43 | |
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| 44 | private CompressionCodecFactory compressionCodecs = null; |
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| 45 | private long start; |
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| 46 | private long pos; |
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| 47 | private long end; |
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| 48 | private LineReader in; |
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| 49 | private int maxLineLength; |
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| 50 | private LongWritable key = null; |
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| 51 | private Text value = null; |
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| 52 | |
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| 53 | public void initialize(InputSplit genericSplit, |
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| 54 | TaskAttemptContext context) throws IOException { |
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| 55 | FileSplit split = (FileSplit) genericSplit; |
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| 56 | Configuration job = context.getConfiguration(); |
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| 57 | this.maxLineLength = job.getInt("mapred.linerecordreader.maxlength", |
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| 58 | Integer.MAX_VALUE); |
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| 59 | start = split.getStart(); |
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| 60 | end = start + split.getLength(); |
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| 61 | final Path file = split.getPath(); |
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| 62 | compressionCodecs = new CompressionCodecFactory(job); |
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| 63 | final CompressionCodec codec = compressionCodecs.getCodec(file); |
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| 64 | |
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| 65 | // open the file and seek to the start of the split |
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| 66 | FileSystem fs = file.getFileSystem(job); |
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| 67 | FSDataInputStream fileIn = fs.open(split.getPath()); |
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| 68 | boolean skipFirstLine = false; |
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| 69 | if (codec != null) { |
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| 70 | in = new LineReader(codec.createInputStream(fileIn), job); |
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| 71 | end = Long.MAX_VALUE; |
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| 72 | } else { |
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| 73 | if (start != 0) { |
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| 74 | skipFirstLine = true; |
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| 75 | --start; |
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| 76 | fileIn.seek(start); |
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| 77 | } |
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| 78 | in = new LineReader(fileIn, job); |
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| 79 | } |
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| 80 | if (skipFirstLine) { // skip first line and re-establish "start". |
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| 81 | start += in.readLine(new Text(), 0, |
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| 82 | (int)Math.min((long)Integer.MAX_VALUE, end - start)); |
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| 83 | } |
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| 84 | this.pos = start; |
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| 85 | } |
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| 86 | |
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| 87 | public boolean nextKeyValue() throws IOException { |
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| 88 | if (key == null) { |
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| 89 | key = new LongWritable(); |
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| 90 | } |
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| 91 | key.set(pos); |
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| 92 | if (value == null) { |
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| 93 | value = new Text(); |
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| 94 | } |
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| 95 | int newSize = 0; |
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| 96 | while (pos < end) { |
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| 97 | newSize = in.readLine(value, maxLineLength, |
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| 98 | Math.max((int)Math.min(Integer.MAX_VALUE, end-pos), |
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| 99 | maxLineLength)); |
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| 100 | if (newSize == 0) { |
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| 101 | break; |
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| 102 | } |
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| 103 | pos += newSize; |
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| 104 | if (newSize < maxLineLength) { |
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| 105 | break; |
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| 106 | } |
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| 107 | |
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| 108 | // line too long. try again |
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| 109 | LOG.info("Skipped line of size " + newSize + " at pos " + |
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| 110 | (pos - newSize)); |
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| 111 | } |
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| 112 | if (newSize == 0) { |
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| 113 | key = null; |
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| 114 | value = null; |
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| 115 | return false; |
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| 116 | } else { |
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| 117 | return true; |
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| 118 | } |
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| 119 | } |
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| 120 | |
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| 121 | @Override |
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| 122 | public LongWritable getCurrentKey() { |
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| 123 | return key; |
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| 124 | } |
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| 125 | |
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| 126 | @Override |
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| 127 | public Text getCurrentValue() { |
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| 128 | return value; |
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| 129 | } |
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| 130 | |
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| 131 | /** |
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| 132 | * Get the progress within the split |
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| 133 | */ |
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| 134 | public float getProgress() { |
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| 135 | if (start == end) { |
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| 136 | return 0.0f; |
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| 137 | } else { |
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| 138 | return Math.min(1.0f, (pos - start) / (float)(end - start)); |
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| 139 | } |
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| 140 | } |
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| 141 | |
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| 142 | public synchronized void close() throws IOException { |
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| 143 | if (in != null) { |
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| 144 | in.close(); |
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| 145 | } |
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| 146 | } |
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| 147 | } |
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