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.mapred;
020
021 import java.io.IOException;
022
023 import org.apache.hadoop.classification.InterfaceAudience;
024 import org.apache.hadoop.classification.InterfaceStability;
025
026 /**
027 * Expert: Generic interface for {@link Mapper}s.
028 *
029 * <p>Custom implementations of <code>MapRunnable</code> can exert greater
030 * control on map processing e.g. multi-threaded, asynchronous mappers etc.</p>
031 *
032 * @see Mapper
033 */
034 @InterfaceAudience.Public
035 @InterfaceStability.Stable
036 public interface MapRunnable<K1, V1, K2, V2>
037 extends JobConfigurable {
038
039 /**
040 * Start mapping input <tt><key, value></tt> pairs.
041 *
042 * <p>Mapping of input records to output records is complete when this method
043 * returns.</p>
044 *
045 * @param input the {@link RecordReader} to read the input records.
046 * @param output the {@link OutputCollector} to collect the outputrecords.
047 * @param reporter {@link Reporter} to report progress, status-updates etc.
048 * @throws IOException
049 */
050 void run(RecordReader<K1, V1> input, OutputCollector<K2, V2> output,
051 Reporter reporter)
052 throws IOException;
053 }