    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.flow.hadoop.stream;
    022
    023    import java.util.List;
    024
    025    import cascading.flow.FlowElement;
    026    import cascading.flow.hadoop.HadoopFlowProcess;
    027    import cascading.flow.hadoop.HadoopFlowStep;
    028    import cascading.flow.stream.Duct;
    029    import cascading.flow.stream.Gate;
    030    import cascading.flow.stream.SinkStage;
    031    import cascading.flow.stream.SpliceGate;
    032    import cascading.flow.stream.StepStreamGraph;
    033    import cascading.pipe.CoGroup;
    034    import cascading.pipe.Group;
    035    import cascading.pipe.GroupBy;
    036    import cascading.pipe.HashJoin;
    037    import cascading.tap.Tap;
    038
    039    /**
    040     *
    041     */
    042    public class HadoopReduceStreamGraph extends StepStreamGraph
    043      {
    044      public HadoopReduceStreamGraph( HadoopFlowProcess flowProcess, HadoopFlowStep step )
    045        {
    046        super( flowProcess, step );
    047
    048        buildGraph();
    049
    050        setTraps();
    051        setScopes();
    052
    053        printGraph( step.getID(), "reduce", flowProcess.getCurrentSliceNum() );
    054
    055        bind();
    056        }
    057
    058      protected void buildGraph()
    059        {
    060        Group group = step.getGroup();
    061
    062        Duct rhsDuct;
    063
    064        if( group.isGroupBy() )
    065          rhsDuct = new HadoopGroupByGate( flowProcess, (GroupBy) group, SpliceGate.Role.source );
    066        else
    067          rhsDuct = new HadoopCoGroupGate( flowProcess, (CoGroup) group, SpliceGate.Role.source );
    068
    069        addHead( rhsDuct );
    070
    071        handleDuct( group, rhsDuct );
    072        }
    073
    074      @Override
    075      protected SinkStage createSinkStage( Tap element )
    076        {
    077        return new HadoopSinkStage( flowProcess, element );
    078        }
    079
    080      protected Gate createCoGroupGate( CoGroup element )
    081        {
    082        throw new IllegalStateException( "should not happen" );
    083        }
    084
    085      protected Gate createGroupByGate( GroupBy element )
    086        {
    087        throw new IllegalStateException( "should not happen" );
    088        }
    089
    090      @Override
    091      protected Gate createHashJoinGate( HashJoin join )
    092        {
    093        throw new IllegalStateException( "should not happen" );
    094        }
    095
    096      protected boolean stopOnElement( FlowElement lhsElement, List<FlowElement> successors )
    097        {
    098        if( successors.isEmpty() )
    099          {
    100          if( !( lhsElement instanceof Tap ) )
    101            throw new IllegalStateException( "expected a Tap instance" );
    102
    103          return true;
    104          }
    105
    106        return false;
    107        }
    108      }