001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.apache.reef.wake.impl; 020 021import org.apache.reef.wake.EventHandler; 022 023import java.util.concurrent.atomic.AtomicInteger; 024 025/** 026 * An EventHandler that blocks until a set number of Events has been received. 027 * Once they have been received, the downstream event handler is called with 028 * the <i>last event</i> received. The handler resets atomically to start 029 * receiving the next batch of events. 030 * <p> 031 * onNext is thread safe 032 * 033 * @param <T> type of events 034 * @see BlockingEventHandler 035 */ 036public final class BlockingSignalEventHandler<T> implements EventHandler<T> { 037 038 private final int expectedSize; 039 private final EventHandler<T> destination; 040 private final AtomicInteger cursor; 041 042 public BlockingSignalEventHandler(final int expectedSize, final EventHandler<T> destination) { 043 this.expectedSize = expectedSize; 044 this.destination = destination; 045 this.cursor = new AtomicInteger(0); 046 } 047 048 @Override 049 public void onNext(final T event) { 050 final int newSize = this.cursor.incrementAndGet(); 051 052 if (newSize % expectedSize == 0) { 053 this.destination.onNext(event); 054 } 055 } 056}