| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.hadoop.mapreduce.task.reduce; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.fs.FileSystem; |
| import org.apache.hadoop.fs.LocalDirAllocator; |
| import org.apache.hadoop.fs.Path; |
| import org.apache.hadoop.io.compress.CompressionCodec; |
| import org.apache.hadoop.mapred.Counters; |
| import org.apache.hadoop.mapred.JobConf; |
| import org.apache.hadoop.mapred.MapOutputFile; |
| import org.apache.hadoop.mapred.RawKeyValueIterator; |
| import org.apache.hadoop.mapred.Reducer; |
| import org.apache.hadoop.mapred.Reporter; |
| import org.apache.hadoop.mapred.Task.CombineOutputCollector; |
| import org.apache.hadoop.mapreduce.TaskAttemptID; |
| import org.apache.hadoop.util.Progress; |
| |
| import java.io.IOException; |
| |
| /** |
| * An interface for a reduce side merge that works with the default Shuffle |
| * implementation. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Unstable |
| public interface MergeManager<K, V> { |
| /** |
| * To wait until merge has some freed resources available so that it can |
| * accept shuffled data. This will be called before a network connection is |
| * established to get the map output. |
| */ |
| public void waitForResource() throws InterruptedException; |
| |
| /** |
| * To reserve resources for data to be shuffled. This will be called after |
| * a network connection is made to shuffle the data. |
| * @param mapId mapper from which data will be shuffled. |
| * @param requestedSize size in bytes of data that will be shuffled. |
| * @param fetcher id of the map output fetcher that will shuffle the data. |
| * @return a MapOutput object that can be used by shuffle to shuffle data. If |
| * required resources cannot be reserved immediately, a null can be returned. |
| */ |
| public MapOutput<K, V> reserve(TaskAttemptID mapId, long requestedSize, |
| int fetcher) throws IOException; |
| |
| /** |
| * Called at the end of shuffle. |
| * @return a key value iterator object. |
| */ |
| public RawKeyValueIterator close() throws Throwable; |
| } |