| /** |
| * 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.oozie.util; |
| |
| import java.util.Iterator; |
| import java.util.concurrent.TimeUnit; |
| |
| public class PollablePriorityDelayQueue<E> extends PriorityDelayQueue<E> { |
| |
| public PollablePriorityDelayQueue(int priorities, long maxWait, TimeUnit unit, int maxSize) { |
| super(priorities, maxWait, unit, maxSize); |
| } |
| |
| /** |
| * Retrieve and remove the head of this queue if it is eligible to poll. If not, iterate next element until find |
| * the one which is eligible to poll from queue. |
| * |
| * Return <tt>null</tt> if this queue has no elements eligible to run. |
| * |
| * <p> |
| * Invocations to this method run the anti-starvation (once every interval check). |
| * |
| * @return the element of this queue, for which eligibleToPoll is true. |
| */ |
| @Override |
| public QueueElement<E> poll() { |
| lock.lock(); |
| try { |
| antiStarvation(); |
| QueueElement<E> e = null; |
| int i = priorities; |
| for (; e == null && i > 0; i--) { |
| e = queues[i - 1].peek(); |
| if (eligibleToPoll(e)) { |
| e = queues[i - 1].poll(); |
| } |
| else { |
| if (e != null) { |
| debug("poll(): the peek element [{0}], from P[{1}] is not eligible to poll", e.getElement().toString(), i); |
| } |
| e = null; |
| Iterator<QueueElement<E>> iter = queues[i - 1].iterator(); |
| while(e == null && iter.hasNext()) { |
| e = iter.next(); |
| if (e.getDelay(TimeUnit.MILLISECONDS) <= 0 && eligibleToPoll(e)) { |
| queues[i - 1].remove(e); |
| } |
| else { |
| debug("poll(): the iterator element [{0}], from P[{1}] is not eligible to poll", e.getElement().toString(), i); |
| e = null; |
| } |
| } |
| } |
| } |
| if (e != null) { |
| if (currentSize != null) { |
| currentSize.decrementAndGet(); |
| } |
| e.inQueue = false; |
| debug("poll(): [{0}], from P[{1}]", e.getElement().toString(), i); |
| } |
| return e; |
| } |
| finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Method for checking the QueueElement eligible to poll before remove it from queue. |
| * <p> |
| * This method should be overriden for checking purposes. |
| * |
| * @param element the element to check |
| */ |
| protected boolean eligibleToPoll(QueueElement<?> element) { |
| return true; |
| } |
| } |