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.io.IOException; 024import java.net.URI; 025 026import cascading.flow.FlowProcess; 027import org.apache.hadoop.conf.Configuration; 028import org.apache.hadoop.filecache.DistributedCache; 029import org.apache.hadoop.fs.Path; 030 031/** 032 * Class DistCacheTap is a Tap decorator for Hfs and can be used to move a file to the 033 * {@link org.apache.hadoop.filecache.DistributedCache} on read when accessed cluster side. 034 * <p/> 035 * This is useful for {@link cascading.pipe.HashJoin}s. 036 * <p/> 037 * The distributed cache is only used when the Tap is used as a source. If the DistCacheTap is used as a sink, 038 * it will delegate to the provided parent instance and not use the DistributedCache. 039 */ 040public class DistCacheTap extends BaseDistCacheTap 041 { 042 /** 043 * Constructs a new DistCacheTap instance with the given Hfs. 044 * 045 * @param parent an Hfs or GlobHfs instance representing a small file. 046 */ 047 public DistCacheTap( Hfs parent ) 048 { 049 super( parent ); 050 } 051 052 @Override 053 protected Path[] getLocalCacheFiles( FlowProcess<? extends Configuration> flowProcess ) throws IOException 054 { 055 return DistributedCache.getLocalCacheFiles( flowProcess.getConfig() ); 056 } 057 058 @Override 059 protected void addLocalCacheFiles( Configuration conf, URI uri ) 060 { 061 DistributedCache.addCacheFile( uri, conf ); 062 } 063 }