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