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 */
018package org.apache.hadoop.mapreduce.lib.input;
019
020import java.util.Collections;
021import java.util.HashMap;
022import java.util.Map;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026import org.apache.hadoop.conf.Configuration;
027import org.apache.hadoop.fs.Path;
028import org.apache.hadoop.mapreduce.InputFormat;
029import org.apache.hadoop.mapreduce.Job;
030import org.apache.hadoop.mapreduce.JobContext;
031import org.apache.hadoop.mapreduce.Mapper;
032import org.apache.hadoop.util.ReflectionUtils;
033
034/**
035 * This class supports MapReduce jobs that have multiple input paths with
036 * a different {@link InputFormat} and {@link Mapper} for each path 
037 */
038@InterfaceAudience.Public
039@InterfaceStability.Stable
040public class MultipleInputs {
041  public static final String DIR_FORMATS = 
042    "mapreduce.input.multipleinputs.dir.formats";
043  public static final String DIR_MAPPERS = 
044    "mapreduce.input.multipleinputs.dir.mappers";
045  
046  /**
047   * Add a {@link Path} with a custom {@link InputFormat} to the list of
048   * inputs for the map-reduce job.
049   * 
050   * @param job The {@link Job}
051   * @param path {@link Path} to be added to the list of inputs for the job
052   * @param inputFormatClass {@link InputFormat} class to use for this path
053   */
054  @SuppressWarnings("unchecked")
055  public static void addInputPath(Job job, Path path,
056      Class<? extends InputFormat> inputFormatClass) {
057    String inputFormatMapping = path.toString() + ";"
058       + inputFormatClass.getName();
059    Configuration conf = job.getConfiguration();
060    String inputFormats = conf.get(DIR_FORMATS);
061    conf.set(DIR_FORMATS,
062       inputFormats == null ? inputFormatMapping : inputFormats + ","
063           + inputFormatMapping);
064
065    job.setInputFormatClass(DelegatingInputFormat.class);
066  }
067
068  /**
069   * Add a {@link Path} with a custom {@link InputFormat} and
070   * {@link Mapper} to the list of inputs for the map-reduce job.
071   * 
072   * @param job The {@link Job}
073   * @param path {@link Path} to be added to the list of inputs for the job
074   * @param inputFormatClass {@link InputFormat} class to use for this path
075   * @param mapperClass {@link Mapper} class to use for this path
076   */
077  @SuppressWarnings("unchecked")
078  public static void addInputPath(Job job, Path path,
079      Class<? extends InputFormat> inputFormatClass,
080      Class<? extends Mapper> mapperClass) {
081
082    addInputPath(job, path, inputFormatClass);
083    Configuration conf = job.getConfiguration();
084    String mapperMapping = path.toString() + ";" + mapperClass.getName();
085    String mappers = conf.get(DIR_MAPPERS);
086    conf.set(DIR_MAPPERS, mappers == null ? mapperMapping
087       : mappers + "," + mapperMapping);
088
089    job.setMapperClass(DelegatingMapper.class);
090  }
091
092  /**
093   * Retrieves a map of {@link Path}s to the {@link InputFormat} class
094   * that should be used for them.
095   * 
096   * @param job The {@link JobContext}
097   * @see #addInputPath(JobConf, Path, Class)
098   * @return A map of paths to inputformats for the job
099   */
100  @SuppressWarnings("unchecked")
101  static Map<Path, InputFormat> getInputFormatMap(JobContext job) {
102    Map<Path, InputFormat> m = new HashMap<Path, InputFormat>();
103    Configuration conf = job.getConfiguration();
104    String[] pathMappings = conf.get(DIR_FORMATS).split(",");
105    for (String pathMapping : pathMappings) {
106      String[] split = pathMapping.split(";");
107      InputFormat inputFormat;
108      try {
109       inputFormat = (InputFormat) ReflectionUtils.newInstance(conf
110           .getClassByName(split[1]), conf);
111      } catch (ClassNotFoundException e) {
112       throw new RuntimeException(e);
113      }
114      m.put(new Path(split[0]), inputFormat);
115    }
116    return m;
117  }
118
119  /**
120   * Retrieves a map of {@link Path}s to the {@link Mapper} class that
121   * should be used for them.
122   * 
123   * @param job The {@link JobContext}
124   * @see #addInputPath(JobConf, Path, Class, Class)
125   * @return A map of paths to mappers for the job
126   */
127  @SuppressWarnings("unchecked")
128  static Map<Path, Class<? extends Mapper>> 
129      getMapperTypeMap(JobContext job) {
130    Configuration conf = job.getConfiguration();
131    if (conf.get(DIR_MAPPERS) == null) {
132      return Collections.emptyMap();
133    }
134    Map<Path, Class<? extends Mapper>> m = 
135      new HashMap<Path, Class<? extends Mapper>>();
136    String[] pathMappings = conf.get(DIR_MAPPERS).split(",");
137    for (String pathMapping : pathMappings) {
138      String[] split = pathMapping.split(";");
139      Class<? extends Mapper> mapClass;
140      try {
141       mapClass = 
142         (Class<? extends Mapper>) conf.getClassByName(split[1]);
143      } catch (ClassNotFoundException e) {
144       throw new RuntimeException(e);
145      }
146      m.put(new Path(split[0]), mapClass);
147    }
148    return m;
149  }
150}