001 /* 002 * Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved. 003 * 004 * Project and contact information: http://www.cascading.org/ 005 * 006 * This file is part of the Cascading project. 007 * 008 * Licensed under the Apache License, Version 2.0 (the "License"); 009 * you may not use this file except in compliance with the License. 010 * You may obtain a copy of the License at 011 * 012 * http://www.apache.org/licenses/LICENSE-2.0 013 * 014 * Unless required by applicable law or agreed to in writing, software 015 * distributed under the License is distributed on an "AS IS" BASIS, 016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 017 * See the License for the specific language governing permissions and 018 * limitations under the License. 019 */ 020 021 package cascading.tap.hadoop; 022 023 import java.beans.ConstructorProperties; 024 import java.io.IOException; 025 026 import cascading.flow.FlowProcess; 027 import cascading.tap.SinkMode; 028 import cascading.tap.Tap; 029 import cascading.tap.TapException; 030 import cascading.tap.hadoop.io.HadoopTupleEntrySchemeIterator; 031 import cascading.tap.hadoop.io.MultiInputSplit; 032 import cascading.tap.hadoop.io.TapOutputCollector; 033 import cascading.tap.partition.BasePartitionTap; 034 import cascading.tap.partition.Partition; 035 import cascading.tuple.TupleEntrySchemeCollector; 036 import cascading.tuple.TupleEntrySchemeIterator; 037 import org.apache.hadoop.fs.Path; 038 import org.apache.hadoop.mapred.JobConf; 039 import org.apache.hadoop.mapred.OutputCollector; 040 import org.apache.hadoop.mapred.RecordReader; 041 042 /** 043 * Class PartitionTap can be used to write tuple streams out to files and sub-directories based on the values in the 044 * current {@link cascading.tuple.Tuple} instance. 045 * <p/> 046 * The constructor takes a {@link cascading.tap.hadoop.Hfs} {@link cascading.tap.Tap} and a {@link Partition} 047 * implementation. This allows Tuple values at given positions to be used as directory names. 048 * <p/> 049 * Note that Hadoop can only sink to directories, and all files in those directories are "part-xxxxx" files. 050 * <p/> 051 * {@code openWritesThreshold} limits the number of open files to be output to. This value defaults to 300 files. 052 * Each time the threshold is exceeded, 10% of the least recently used open files will be closed. 053 * <p/> 054 * PartitionTap will populate a given {@code partition} without regard to case of the values being used. Thus 055 * the resulting paths {@code 2012/June/} and {@code 2012/june/} will likely result in two open files into the same 056 * location. Forcing the case to be consistent with a custom Partition implementation or an upstream 057 * {@link cascading.operation.Function} is recommended, see {@link cascading.operation.expression.ExpressionFunction}. 058 * <p/> 059 * Though Hadoop has no mechanism to prevent simultaneous writes to a directory from multiple jobs, it doesn't mean 060 * its safe to do so. Same is true with the PartitionTap. Interleaving writes to a common parent (root) directory 061 * across multiple flows will very likely lead to data loss. 062 */ 063 public class PartitionTap extends BasePartitionTap<JobConf, RecordReader, OutputCollector> 064 { 065 /** 066 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 067 * base path and default {@link cascading.scheme.Scheme}, and the partition. 068 * 069 * @param parent of type Tap 070 * @param partition of type String 071 */ 072 @ConstructorProperties({"parent", "partition"}) 073 public PartitionTap( Hfs parent, Partition partition ) 074 { 075 this( parent, partition, OPEN_WRITES_THRESHOLD_DEFAULT ); 076 } 077 078 /** 079 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 080 * base path and default {@link cascading.scheme.Scheme}, and the partition. 081 * <p/> 082 * {@code openWritesThreshold} limits the number of open files to be output to. 083 * 084 * @param parent of type Hfs 085 * @param partition of type String 086 * @param openWritesThreshold of type int 087 */ 088 @ConstructorProperties({"parent", "partition", "openWritesThreshold"}) 089 public PartitionTap( Hfs parent, Partition partition, int openWritesThreshold ) 090 { 091 super( parent, partition, openWritesThreshold ); 092 } 093 094 /** 095 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 096 * base path and default {@link cascading.scheme.Scheme}, and the partition. 097 * 098 * @param parent of type Tap 099 * @param partition of type String 100 * @param sinkMode of type SinkMode 101 */ 102 @ConstructorProperties({"parent", "partition", "sinkMode"}) 103 public PartitionTap( Hfs parent, Partition partition, SinkMode sinkMode ) 104 { 105 super( parent, partition, sinkMode ); 106 } 107 108 /** 109 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 110 * base path and default {@link cascading.scheme.Scheme}, and the partition. 111 * <p/> 112 * {@code keepParentOnDelete}, when set to true, prevents the parent Tap from being deleted when {@link #deleteResource(Object)} 113 * is called, typically an issue when used inside a {@link cascading.cascade.Cascade}. 114 * 115 * @param parent of type Tap 116 * @param partition of type String 117 * @param sinkMode of type SinkMode 118 * @param keepParentOnDelete of type boolean 119 */ 120 @ConstructorProperties({"parent", "partition", "sinkMode", "keepParentOnDelete"}) 121 public PartitionTap( Hfs parent, Partition partition, SinkMode sinkMode, boolean keepParentOnDelete ) 122 { 123 this( parent, partition, sinkMode, keepParentOnDelete, OPEN_WRITES_THRESHOLD_DEFAULT ); 124 } 125 126 /** 127 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 128 * base path and default {@link cascading.scheme.Scheme}, and the partition. 129 * <p/> 130 * {@code keepParentOnDelete}, when set to true, prevents the parent Tap from being deleted when {@link #deleteResource(Object)} 131 * is called, typically an issue when used inside a {@link cascading.cascade.Cascade}. 132 * <p/> 133 * {@code openWritesThreshold} limits the number of open files to be output to. 134 * 135 * @param parent of type Tap 136 * @param partition of type String 137 * @param sinkMode of type SinkMode 138 * @param keepParentOnDelete of type boolean 139 * @param openWritesThreshold of type int 140 */ 141 @ConstructorProperties({"parent", "partition", "sinkMode", "keepParentOnDelete", "openWritesThreshold"}) 142 public PartitionTap( Hfs parent, Partition partition, SinkMode sinkMode, boolean keepParentOnDelete, int openWritesThreshold ) 143 { 144 super( parent, partition, sinkMode, keepParentOnDelete, openWritesThreshold ); 145 } 146 147 @Override 148 protected TupleEntrySchemeCollector createTupleEntrySchemeCollector( FlowProcess<JobConf> flowProcess, Tap parent, String path, long sequence ) throws IOException 149 { 150 TapOutputCollector outputCollector = new TapOutputCollector( flowProcess, parent, path, sequence ); 151 152 return new TupleEntrySchemeCollector<JobConf, OutputCollector>( flowProcess, parent, outputCollector ); 153 } 154 155 @Override 156 protected TupleEntrySchemeIterator createTupleEntrySchemeIterator( FlowProcess<JobConf> flowProcess, Tap parent, String path, RecordReader recordReader ) throws IOException 157 { 158 return new HadoopTupleEntrySchemeIterator( flowProcess, new Hfs( parent.getScheme(), path ), recordReader ); 159 } 160 161 @Override 162 protected String getCurrentIdentifier( FlowProcess<JobConf> flowProcess ) 163 { 164 String identifier = flowProcess.getStringProperty( MultiInputSplit.CASCADING_SOURCE_PATH ); // set on current split 165 166 if( identifier == null ) 167 return null; 168 169 return new Path( identifier ).getParent().toString(); // drop part-xxxx 170 } 171 172 @Override 173 public void sourceConfInit( FlowProcess<JobConf> flowProcess, JobConf conf ) 174 { 175 try 176 { 177 String[] childPartitions = getChildPartitionIdentifiers( flowProcess, true ); 178 179 ( (Hfs) getParent() ).applySourceConfInitIdentifiers( flowProcess, conf, childPartitions ); 180 } 181 catch( IOException exception ) 182 { 183 throw new TapException( "unable to retrieve child partitions", exception ); 184 } 185 } 186 }