001/* 002 * Copyright (c) 2007-2017 Xplenty, 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.flow.stream.element; 022 023import java.util.concurrent.atomic.AtomicInteger; 024 025import cascading.flow.FlowElement; 026import cascading.flow.FlowProcess; 027import cascading.flow.stream.duct.Collapsing; 028import cascading.flow.stream.duct.Duct; 029import cascading.flow.stream.graph.StreamGraph; 030import cascading.tuple.TupleEntry; 031 032/** 033 * 034 */ 035public class MergeStage extends ElementStage<TupleEntry, TupleEntry> implements Collapsing 036 { 037 private boolean started = false; 038 protected final AtomicInteger completeCount = new AtomicInteger( 0 ); 039 private int numIncomingPaths; 040 041 public MergeStage( FlowProcess flowProcess, FlowElement flowElement ) 042 { 043 super( flowProcess, flowElement ); 044 } 045 046 @Override 047 public void bind( StreamGraph streamGraph ) 048 { 049 super.bind( streamGraph ); 050 051 numIncomingPaths = streamGraph.findAllPreviousFor( this ).length; 052 } 053 054 @Override 055 public void initialize() 056 { 057 super.initialize(); 058 059 completeCount.set( numIncomingPaths ); 060 } 061 062 @Override 063 public synchronized void start( Duct previous ) 064 { 065 if( started ) 066 return; 067 068 super.start( previous ); 069 started = true; 070 } 071 072 @Override 073 public void complete( Duct previous ) 074 { 075 if( completeCount.decrementAndGet() != 0 ) 076 return; 077 078 super.complete( previous ); 079 completeCount.set( numIncomingPaths ); 080 } 081 }