[120] | 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 3 | * or more contributor license agreements. See the NOTICE file |
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| 4 | * distributed with this work for additional information |
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| 5 | * regarding copyright ownership. The ASF licenses this file |
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| 6 | * to you under the Apache License, Version 2.0 (the |
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| 7 | * "License"); you may not use this file except in compliance |
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| 8 | * with the License. You may obtain a copy of the License at |
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| 9 | * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 11 | * |
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| 12 | * Unless required by applicable law or agreed to in writing, software |
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| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 15 | * See the License for the specific language governing permissions and |
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| 16 | * limitations under the License. |
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| 17 | */ |
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| 18 | |
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| 19 | package org.apache.hadoop.mapreduce; |
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| 20 | |
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| 21 | import java.io.IOException; |
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| 22 | |
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| 23 | /** |
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| 24 | * <code>OutputCommitter</code> describes the commit of task output for a |
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| 25 | * Map-Reduce job. |
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| 26 | * |
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| 27 | * <p>The Map-Reduce framework relies on the <code>OutputCommitter</code> of |
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| 28 | * the job to:<p> |
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| 29 | * <ol> |
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| 30 | * <li> |
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| 31 | * Setup the job during initialization. For example, create the temporary |
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| 32 | * output directory for the job during the initialization of the job. |
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| 33 | * </li> |
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| 34 | * <li> |
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| 35 | * Cleanup the job after the job completion. For example, remove the |
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| 36 | * temporary output directory after the job completion. |
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| 37 | * </li> |
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| 38 | * <li> |
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| 39 | * Setup the task temporary output. |
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| 40 | * </li> |
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| 41 | * <li> |
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| 42 | * Check whether a task needs a commit. This is to avoid the commit |
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| 43 | * procedure if a task does not need commit. |
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| 44 | * </li> |
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| 45 | * <li> |
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| 46 | * Commit of the task output. |
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| 47 | * </li> |
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| 48 | * <li> |
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| 49 | * Discard the task commit. |
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| 50 | * </li> |
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| 51 | * </ol> |
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| 52 | * |
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| 53 | * @see org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter |
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| 54 | * @see JobContext |
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| 55 | * @see TaskAttemptContext |
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| 56 | * |
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| 57 | */ |
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| 58 | public abstract class OutputCommitter { |
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| 59 | /** |
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| 60 | * For the framework to setup the job output during initialization |
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| 61 | * |
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| 62 | * @param jobContext Context of the job whose output is being written. |
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| 63 | * @throws IOException if temporary output could not be created |
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| 64 | */ |
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| 65 | public abstract void setupJob(JobContext jobContext) throws IOException; |
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| 66 | |
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| 67 | /** |
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| 68 | * For cleaning up the job's output after job completion |
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| 69 | * |
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| 70 | * @param jobContext Context of the job whose output is being written. |
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| 71 | * @throws IOException |
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| 72 | */ |
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| 73 | public abstract void cleanupJob(JobContext jobContext) throws IOException; |
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| 74 | |
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| 75 | /** |
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| 76 | * Sets up output for the task. |
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| 77 | * |
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| 78 | * @param taskContext Context of the task whose output is being written. |
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| 79 | * @throws IOException |
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| 80 | */ |
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| 81 | public abstract void setupTask(TaskAttemptContext taskContext) |
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| 82 | throws IOException; |
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| 83 | |
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| 84 | /** |
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| 85 | * Check whether task needs a commit |
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| 86 | * |
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| 87 | * @param taskContext |
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| 88 | * @return true/false |
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| 89 | * @throws IOException |
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| 90 | */ |
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| 91 | public abstract boolean needsTaskCommit(TaskAttemptContext taskContext) |
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| 92 | throws IOException; |
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| 93 | |
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| 94 | /** |
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| 95 | * To promote the task's temporary output to final output location |
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| 96 | * |
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| 97 | * The task's output is moved to the job's output directory. |
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| 98 | * |
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| 99 | * @param taskContext Context of the task whose output is being written. |
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| 100 | * @throws IOException if commit is not |
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| 101 | */ |
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| 102 | public abstract void commitTask(TaskAttemptContext taskContext) |
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| 103 | throws IOException; |
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| 104 | |
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| 105 | /** |
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| 106 | * Discard the task output |
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| 107 | * |
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| 108 | * @param taskContext |
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| 109 | * @throws IOException |
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| 110 | */ |
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| 111 | public abstract void abortTask(TaskAttemptContext taskContext) |
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| 112 | throws IOException; |
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| 113 | } |
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