    001/*
    002 * Copyright (c) 2007-2016 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.util;
    022
    023import java.io.IOException;
    024import java.util.Set;
    025
    026import cascading.CascadingException;
    027import cascading.flow.FlowProcess;
    028import cascading.flow.planner.Scope;
    029import cascading.scheme.Scheme;
    030import cascading.scheme.SinkCall;
    031import cascading.scheme.SourceCall;
    032import cascading.scheme.hadoop.SequenceFile;
    033import cascading.tap.Tap;
    034import cascading.tap.hadoop.Hfs;
    035import cascading.tuple.Fields;
    036import cascading.tuple.Tuple;
    037import org.apache.hadoop.conf.Configuration;
    038import org.apache.hadoop.fs.Path;
    039import org.apache.hadoop.mapred.OutputCollector;
    040import org.apache.hadoop.mapred.OutputFormat;
    041import org.apache.hadoop.mapred.RecordReader;
    042import org.apache.hadoop.mapred.lib.NullOutputFormat;
    043
    044/** Class TempHfs creates a temporary {@link cascading.tap.Tap} instance for use internally. */
    045public class TempHfs extends Hfs
    046  {
    047  /** Field name */
    048  final String name;
    049  /** Field schemeClass */
    050  private Class<? extends Scheme> schemeClass;
    051  /** Field temporaryPath */
    052
    053  /** Class NullScheme is a noop scheme used as a placeholder */
    054  private static class NullScheme extends Scheme<Configuration, RecordReader, OutputCollector, Object, Object>
    055    {
    056    @Override
    057    public void sourceConfInit( FlowProcess<? extends Configuration> flowProcess, Tap<Configuration, RecordReader, OutputCollector> tap, Configuration conf )
    058      {
    059      // do nothing
    060      }
    061
    062    @Override
    063    public void sinkConfInit( FlowProcess<? extends Configuration> flowProcess, Tap<Configuration, RecordReader, OutputCollector> tap, Configuration conf )
    064      {
    065      conf.setClass( "mapred.output.key.class", Tuple.class, Object.class );
    066      conf.setClass( "mapred.output.value.class", Tuple.class, Object.class );
    067      conf.setClass( "mapred.output.format.class", NullOutputFormat.class, OutputFormat.class );
    068      }
    069
    070    @Override
    071    public boolean source( FlowProcess<? extends Configuration> flowProcess, SourceCall<Object, RecordReader> sourceCall ) throws IOException
    072      {
    073      return false;
    074      }
    075
    076    @Override
    077    public void sink( FlowProcess<? extends Configuration> flowProcess, SinkCall<Object, OutputCollector> sinkCall ) throws IOException
    078      {
    079      }
    080    }
    081
    082  /**
    083   * Constructor TempHfs creates a new TempHfs instance.
    084   *
    085   * @param name   of type String
    086   * @param isNull of type boolean
    087   */
    088  public TempHfs( Configuration conf, String name, boolean isNull )
    089    {
    090    super( isNull ? new NullScheme() : new SequenceFile()
    091    {
    092    } );
    093    this.name = name;
    094    this.stringPath = initTemporaryPath( conf, true );
    095    }
    096
    097  /**
    098   * Constructor TempDfs creates a new TempDfs instance.
    099   *
    100   * @param name of type String
    101   */
    102  public TempHfs( Configuration conf, String name, Class<? extends Scheme> schemeClass )
    103    {
    104    this( conf, name, schemeClass, true );
    105    }
    106
    107  public TempHfs( Configuration conf, String name, Class<? extends Scheme> schemeClass, boolean unique )
    108    {
    109    this.name = name;
    110
    111    if( schemeClass == null )
    112      this.schemeClass = SequenceFile.class;
    113    else
    114      this.schemeClass = schemeClass;
    115
    116    this.stringPath = initTemporaryPath( conf, unique );
    117    }
    118
    119  public Class<? extends Scheme> getSchemeClass()
    120    {
    121    return schemeClass;
    122    }
    123
    124  private String initTemporaryPath( Configuration conf, boolean unique )
    125    {
    126    String child = unique ? makeTemporaryPathDirString( name ) : name;
    127
    128    return new Path( getTempPath( conf ), child ).toString();
    129    }
    130
    131  @Override
    132  public Scope outgoingScopeFor( Set<Scope> incomingScopes )
    133    {
    134    Fields fields = incomingScopes.iterator().next().getIncomingTapFields();
    135
    136    setSchemeUsing( fields );
    137
    138    return new Scope( fields );
    139    }
    140
    141  private void setSchemeUsing( Fields fields )
    142    {
    143    try
    144      {
    145      setScheme( schemeClass.getConstructor( Fields.class ).newInstance( fields ) );
    146      }
    147    catch( Exception exception )
    148      {
    149      throw new CascadingException( "unable to create specified scheme: " + schemeClass.getName(), exception );
    150      }
    151    }
    152
    153  @Override
    154  public boolean isTemporary()
    155    {
    156    return true;
    157    }
    158
    159  @Override
    160  public String toString()
    161    {
    162    return getClass().getSimpleName() + "[\"" + getScheme() + "\"]" + "[" + name + "]";
    163    }
    164  }