| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.yarn.event; |
| |
| import java.util.HashMap; |
| import java.util.concurrent.BlockingQueue; |
| import java.util.concurrent.LinkedBlockingQueue; |
| import java.util.concurrent.TimeUnit; |
| |
| @SuppressWarnings("rawtypes") |
| public class DrainDispatcher extends AsyncDispatcher { |
| |
| // flagrant initialize abuse throughout, but safe per |
| // http://java.sun.com/docs/books/jls/third_edition/html/typesValues.html#96595 |
| // and similar grotesqueries |
| private volatile boolean drained = false; |
| private final BlockingQueue<Event> queue; |
| |
| public DrainDispatcher() { |
| this(new LinkedBlockingQueue<Event>()); |
| } |
| |
| private DrainDispatcher(BlockingQueue<Event> eventQueue) { |
| super(new HashMap<Class<? extends Enum>, EventHandler>(), eventQueue); |
| this.queue = eventQueue; |
| } |
| |
| /** |
| * Busy loop waiting for all queued events to drain. |
| */ |
| public void await() { |
| while (!drained) { |
| Thread.yield(); |
| } |
| } |
| |
| @Override |
| Runnable createThread() { |
| return new Runnable() { |
| @Override |
| public void run() { |
| while (!Thread.currentThread().isInterrupted()) { |
| // !drained if dispatch queued new events on this dispatcher |
| drained = queue.isEmpty(); |
| Event event; |
| try { |
| event = queue.take(); |
| } catch(InterruptedException ie) { |
| return; |
| } |
| if (event != null) { |
| dispatch(event); |
| } |
| } |
| } |
| }; |
| } |
| |
| @Override |
| public EventHandler getEventHandler() { |
| final EventHandler actual = super.getEventHandler(); |
| return new EventHandler() { |
| @Override |
| public void handle(Event event) { |
| drained = false; |
| actual.handle(event); |
| } |
| }; |
| } |
| |
| } |