001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019 package org.apache.hadoop.mapreduce.lib.input;
020
021 import java.io.*;
022 import java.lang.reflect.*;
023
024 import org.apache.hadoop.fs.FileSystem;
025
026 import org.apache.hadoop.mapreduce.*;
027 import org.apache.hadoop.classification.InterfaceAudience;
028 import org.apache.hadoop.classification.InterfaceStability;
029 import org.apache.hadoop.conf.Configuration;
030
031 /**
032 * A generic RecordReader that can hand out different recordReaders
033 * for each chunk in a {@link CombineFileSplit}.
034 * A CombineFileSplit can combine data chunks from multiple files.
035 * This class allows using different RecordReaders for processing
036 * these data chunks from different files.
037 * @see CombineFileSplit
038 */
039 @InterfaceAudience.Public
040 @InterfaceStability.Stable
041 public class CombineFileRecordReader<K, V> extends RecordReader<K, V> {
042
043 static final Class [] constructorSignature = new Class []
044 {CombineFileSplit.class,
045 TaskAttemptContext.class,
046 Integer.class};
047
048 protected CombineFileSplit split;
049 protected Constructor<? extends RecordReader<K,V>> rrConstructor;
050 protected TaskAttemptContext context;
051
052 protected int idx;
053 protected long progress;
054 protected RecordReader<K, V> curReader;
055
056 public void initialize(InputSplit split,
057 TaskAttemptContext context) throws IOException, InterruptedException {
058 this.split = (CombineFileSplit)split;
059 this.context = context;
060 if (null != this.curReader) {
061 this.curReader.initialize(split, context);
062 }
063 }
064
065 public boolean nextKeyValue() throws IOException, InterruptedException {
066
067 while ((curReader == null) || !curReader.nextKeyValue()) {
068 if (!initNextRecordReader()) {
069 return false;
070 }
071 }
072 return true;
073 }
074
075 public K getCurrentKey() throws IOException, InterruptedException {
076 return curReader.getCurrentKey();
077 }
078
079 public V getCurrentValue() throws IOException, InterruptedException {
080 return curReader.getCurrentValue();
081 }
082
083 public void close() throws IOException {
084 if (curReader != null) {
085 curReader.close();
086 curReader = null;
087 }
088 }
089
090 /**
091 * return progress based on the amount of data processed so far.
092 */
093 public float getProgress() throws IOException, InterruptedException {
094 long subprogress = 0; // bytes processed in current split
095 if (null != curReader) {
096 // idx is always one past the current subsplit's true index.
097 subprogress = (long)(curReader.getProgress() * split.getLength(idx - 1));
098 }
099 return Math.min(1.0f, (progress + subprogress)/(float)(split.getLength()));
100 }
101
102 /**
103 * A generic RecordReader that can hand out different recordReaders
104 * for each chunk in the CombineFileSplit.
105 */
106 public CombineFileRecordReader(CombineFileSplit split,
107 TaskAttemptContext context,
108 Class<? extends RecordReader<K,V>> rrClass)
109 throws IOException {
110 this.split = split;
111 this.context = context;
112 this.idx = 0;
113 this.curReader = null;
114 this.progress = 0;
115
116 try {
117 rrConstructor = rrClass.getDeclaredConstructor(constructorSignature);
118 rrConstructor.setAccessible(true);
119 } catch (Exception e) {
120 throw new RuntimeException(rrClass.getName() +
121 " does not have valid constructor", e);
122 }
123 initNextRecordReader();
124 }
125
126 /**
127 * Get the record reader for the next chunk in this CombineFileSplit.
128 */
129 protected boolean initNextRecordReader() throws IOException {
130
131 if (curReader != null) {
132 curReader.close();
133 curReader = null;
134 if (idx > 0) {
135 progress += split.getLength(idx-1); // done processing so far
136 }
137 }
138
139 // if all chunks have been processed, nothing more to do.
140 if (idx == split.getNumPaths()) {
141 return false;
142 }
143
144 // get a record reader for the idx-th chunk
145 try {
146 Configuration conf = context.getConfiguration();
147 // setup some helper config variables.
148 conf.set(MRJobConfig.MAP_INPUT_FILE, split.getPath(idx).toString());
149 conf.setLong(MRJobConfig.MAP_INPUT_START, split.getOffset(idx));
150 conf.setLong(MRJobConfig.MAP_INPUT_PATH, split.getLength(idx));
151
152 curReader = rrConstructor.newInstance(new Object []
153 {split, context, Integer.valueOf(idx)});
154
155 if (idx > 0) {
156 // initialize() for the first RecordReader will be called by MapTask;
157 // we're responsible for initializing subsequent RecordReaders.
158 curReader.initialize(split, context);
159 }
160 } catch (Exception e) {
161 throw new RuntimeException (e);
162 }
163 idx++;
164 return true;
165 }
166 }