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.stream;
022    
023    import java.util.concurrent.atomic.AtomicInteger;
024    
025    import cascading.flow.FlowElement;
026    import cascading.flow.FlowProcess;
027    import cascading.tuple.TupleEntry;
028    
029    /**
030     *
031     */
032    public class MergeStage extends ElementStage<TupleEntry, TupleEntry> implements Collapsing
033      {
034      private boolean started = false;
035      protected final AtomicInteger completeCount = new AtomicInteger( 0 );
036      private int numIncomingPaths;
037    
038      public MergeStage( FlowProcess flowProcess, FlowElement flowElement )
039        {
040        super( flowProcess, flowElement );
041        }
042    
043      @Override
044      public void bind( StreamGraph streamGraph )
045        {
046        super.bind( streamGraph );
047    
048        numIncomingPaths = streamGraph.countAllEventingPathsTo( this );
049        }
050    
051      @Override
052      public void initialize()
053        {
054        super.initialize();
055    
056        completeCount.set( numIncomingPaths );
057        }
058    
059      @Override
060      public synchronized void start( Duct previous )
061        {
062        if( started )
063          return;
064    
065        super.start( previous );
066        started = true;
067        }
068    
069      @Override
070      public void complete( Duct previous )
071        {
072        if( completeCount.decrementAndGet() != 0 )
073          return;
074    
075        super.complete( previous );
076        completeCount.set( numIncomingPaths );
077        }
078      }