001/* 002 * Copyright (c) 2007-2015 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 021package cascading.tap.hadoop; 022 023import java.beans.ConstructorProperties; 024import java.io.IOException; 025import java.util.ArrayList; 026import java.util.Iterator; 027import java.util.List; 028 029import cascading.flow.FlowProcess; 030import cascading.tap.SinkMode; 031import cascading.tap.Tap; 032import cascading.tap.TapException; 033import cascading.tap.hadoop.io.CombineInputPartitionTupleEntryIterator; 034import cascading.tap.hadoop.io.HadoopTupleEntrySchemeIterator; 035import cascading.tap.hadoop.io.MultiInputSplit; 036import cascading.tap.hadoop.io.TapOutputCollector; 037import cascading.tap.partition.BasePartitionTap; 038import cascading.tap.partition.Partition; 039import cascading.tuple.Tuple; 040import cascading.tuple.TupleEntryIterableChainIterator; 041import cascading.tuple.TupleEntryIterator; 042import cascading.tuple.TupleEntrySchemeCollector; 043import cascading.tuple.TupleEntrySchemeIterator; 044import org.apache.hadoop.conf.Configuration; 045import org.apache.hadoop.fs.Path; 046import org.apache.hadoop.mapred.OutputCollector; 047import org.apache.hadoop.mapred.RecordReader; 048 049/** 050 * Class PartitionTap can be used to write tuple streams out to files and sub-directories based on the values in the 051 * current {@link cascading.tuple.Tuple} instance. 052 * <p/> 053 * The constructor takes a {@link cascading.tap.hadoop.Hfs} {@link cascading.tap.Tap} and a {@link Partition} 054 * implementation. This allows Tuple values at given positions to be used as directory names during write 055 * operations, and directory names as data during read operations. 056 * <p/> 057 * The key value here is that there is no need to duplicate data values in the directory names and inside 058 * the data files. 059 * <p/> 060 * So only values declared in the parent Tap will be read or written to the underlying file system files. But 061 * fields declared by the {@link Partition} will only be read or written to the directory names. That is, the 062 * PartitionTap instance will sink or source the partition fields, plus the parent Tap fields. The partition 063 * fields and parent Tap fields do not need to have common field names. 064 * <p/> 065 * Note that Hadoop can only sink to directories, and all files in those directories are "part-xxxxx" files. 066 * <p/> 067 * {@code openWritesThreshold} limits the number of open files to be output to. This value defaults to 300 files. 068 * Each time the threshold is exceeded, 10% of the least recently used open files will be closed. 069 * <p/> 070 * PartitionTap will populate a given {@code partition} without regard to case of the values being used. Thus 071 * the resulting paths {@code 2012/June/} and {@code 2012/june/} will likely result in two open files into the same 072 * location. Forcing the case to be consistent with a custom Partition implementation or an upstream 073 * {@link cascading.operation.Function} is recommended, see {@link cascading.operation.expression.ExpressionFunction}. 074 * <p/> 075 * Though Hadoop has no mechanism to prevent simultaneous writes to a directory from multiple jobs, it doesn't mean 076 * its safe to do so. Same is true with the PartitionTap. Interleaving writes to a common parent (root) directory 077 * across multiple flows will very likely lead to data loss. 078 */ 079public class PartitionTap extends BasePartitionTap<Configuration, RecordReader, OutputCollector> 080 { 081 /** 082 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 083 * base path and default {@link cascading.scheme.Scheme}, and the partition. 084 * 085 * @param parent of type Tap 086 * @param partition of type String 087 */ 088 @ConstructorProperties({"parent", "partition"}) 089 public PartitionTap( Hfs parent, Partition partition ) 090 { 091 this( parent, partition, OPEN_WRITES_THRESHOLD_DEFAULT ); 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 * <p/> 098 * {@code openWritesThreshold} limits the number of open files to be output to. 099 * 100 * @param parent of type Hfs 101 * @param partition of type String 102 * @param openWritesThreshold of type int 103 */ 104 @ConstructorProperties({"parent", "partition", "openWritesThreshold"}) 105 public PartitionTap( Hfs parent, Partition partition, int openWritesThreshold ) 106 { 107 super( parent, partition, openWritesThreshold ); 108 } 109 110 /** 111 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 112 * base path and default {@link cascading.scheme.Scheme}, and the partition. 113 * 114 * @param parent of type Tap 115 * @param partition of type String 116 * @param sinkMode of type SinkMode 117 */ 118 @ConstructorProperties({"parent", "partition", "sinkMode"}) 119 public PartitionTap( Hfs parent, Partition partition, SinkMode sinkMode ) 120 { 121 super( parent, partition, sinkMode ); 122 } 123 124 /** 125 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 126 * base path and default {@link cascading.scheme.Scheme}, and the partition. 127 * <p/> 128 * {@code keepParentOnDelete}, when set to true, prevents the parent Tap from being deleted when {@link #deleteResource(Object)} 129 * is called, typically an issue when used inside a {@link cascading.cascade.Cascade}. 130 * 131 * @param parent of type Tap 132 * @param partition of type String 133 * @param sinkMode of type SinkMode 134 * @param keepParentOnDelete of type boolean 135 */ 136 @ConstructorProperties({"parent", "partition", "sinkMode", "keepParentOnDelete"}) 137 public PartitionTap( Hfs parent, Partition partition, SinkMode sinkMode, boolean keepParentOnDelete ) 138 { 139 this( parent, partition, sinkMode, keepParentOnDelete, OPEN_WRITES_THRESHOLD_DEFAULT ); 140 } 141 142 /** 143 * Constructor PartitionTap creates a new PartitionTap instance using the given parent {@link cascading.tap.hadoop.Hfs} Tap as the 144 * base path and default {@link cascading.scheme.Scheme}, and the partition. 145 * <p/> 146 * {@code keepParentOnDelete}, when set to true, prevents the parent Tap from being deleted when {@link #deleteResource(Object)} 147 * is called, typically an issue when used inside a {@link cascading.cascade.Cascade}. 148 * <p/> 149 * {@code openWritesThreshold} limits the number of open files to be output to. 150 * 151 * @param parent of type Tap 152 * @param partition of type String 153 * @param sinkMode of type SinkMode 154 * @param keepParentOnDelete of type boolean 155 * @param openWritesThreshold of type int 156 */ 157 @ConstructorProperties({"parent", "partition", "sinkMode", "keepParentOnDelete", "openWritesThreshold"}) 158 public PartitionTap( Hfs parent, Partition partition, SinkMode sinkMode, boolean keepParentOnDelete, int openWritesThreshold ) 159 { 160 super( parent, partition, sinkMode, keepParentOnDelete, openWritesThreshold ); 161 } 162 163 @Override 164 protected TupleEntrySchemeCollector createTupleEntrySchemeCollector( FlowProcess<? extends Configuration> flowProcess, Tap parent, String path, long sequence ) throws IOException 165 { 166 TapOutputCollector outputCollector = new TapOutputCollector( flowProcess, parent, path, sequence ); 167 168 return new TupleEntrySchemeCollector<Configuration, OutputCollector>( flowProcess, parent, outputCollector ); 169 } 170 171 @Override 172 protected TupleEntrySchemeIterator createTupleEntrySchemeIterator( FlowProcess<? extends Configuration> flowProcess, Tap parent, String path, RecordReader recordReader ) throws IOException 173 { 174 return new HadoopTupleEntrySchemeIterator( flowProcess, new Hfs( parent.getScheme(), path ), recordReader ); 175 } 176 177 @Override 178 protected String getCurrentIdentifier( FlowProcess<? extends Configuration> flowProcess ) 179 { 180 String identifier = flowProcess.getStringProperty( MultiInputSplit.CASCADING_SOURCE_PATH ); // set on current split 181 182 if( identifier == null ) 183 { 184 if( flowProcess.getBooleanProperty( HfsProps.COMBINE_INPUT_FILES, false ) ) 185 throw new TapException( "combined input format support, via '" + HfsProps.COMBINE_INPUT_FILES + "', may not be enabled for use with the PartitionTap" ); 186 187 throw new TapException( "unable to retrieve the current file being processed, '" + MultiInputSplit.CASCADING_SOURCE_PATH + "' is not set" ); 188 } 189 190 return new Path( identifier ).getParent().toString(); // drop part-xxxx 191 } 192 193 @Override 194 public void sourceConfInit( FlowProcess<? extends Configuration> flowProcess, Configuration conf ) 195 { 196 try 197 { 198 String[] childPartitions = getChildPartitionIdentifiers( flowProcess, true ); 199 200 ( (Hfs) getParent() ).applySourceConfInitIdentifiers( flowProcess, conf, childPartitions ); 201 } 202 catch( IOException exception ) 203 { 204 throw new TapException( "unable to retrieve child partitions", exception ); 205 } 206 } 207 208 @Override 209 public TupleEntryIterator openForRead( FlowProcess<? extends Configuration> flowProcess, RecordReader input ) throws IOException 210 { 211 if( flowProcess.getBooleanProperty( HfsProps.COMBINE_INPUT_FILES, false ) ) 212 return new CombinePartitionIterator( flowProcess, input ); 213 214 return super.openForRead( flowProcess, input ); 215 } 216 217 private class CombinePartitionIterator extends TupleEntryIterableChainIterator 218 { 219 public CombinePartitionIterator( final FlowProcess<? extends Configuration> flowProcess, RecordReader input ) throws IOException 220 { 221 super( getSourceFields() ); 222 223 List<Iterator<Tuple>> iterators = new ArrayList<Iterator<Tuple>>(); 224 225 if( input == null ) 226 throw new IOException( "input cannot be null" ); 227 228 String identifier = parent.getFullIdentifier( flowProcess ); 229 230 iterators.add( createPartitionEntryIterator( flowProcess, input, identifier ) ); 231 232 reset( iterators ); 233 } 234 235 private CombineInputPartitionTupleEntryIterator createPartitionEntryIterator( FlowProcess<? extends Configuration> flowProcess, RecordReader input, String parentIdentifier ) throws IOException 236 { 237 TupleEntrySchemeIterator schemeIterator = createTupleEntrySchemeIterator( flowProcess, parent, null, input ); 238 239 return new CombineInputPartitionTupleEntryIterator( flowProcess, getSourceFields(), partition, parentIdentifier, schemeIterator ); 240 } 241 } 242 }