| /* |
| * 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.tomcat.util.threads; |
| |
| import java.util.Collection; |
| import java.util.concurrent.LinkedBlockingQueue; |
| import java.util.concurrent.RejectedExecutionException; |
| import java.util.concurrent.TimeUnit; |
| |
| /** |
| * As task queue specifically designed to run with a thread pool executor. The |
| * task queue is optimised to properly utilize threads within a thread pool |
| * executor. If you use a normal queue, the executor will spawn threads when |
| * there are idle threads and you wont be able to force items onto the queue |
| * itself. |
| */ |
| public class TaskQueue extends LinkedBlockingQueue<Runnable> { |
| |
| private static final long serialVersionUID = 1L; |
| |
| private volatile ThreadPoolExecutor parent = null; |
| |
| // No need to be volatile. This is written and read in a single thread |
| // (when stopping a context and firing the listeners) |
| private Integer forcedRemainingCapacity = null; |
| |
| public TaskQueue() { |
| super(); |
| } |
| |
| public TaskQueue(int capacity) { |
| super(capacity); |
| } |
| |
| public TaskQueue(Collection<? extends Runnable> c) { |
| super(c); |
| } |
| |
| public void setParent(ThreadPoolExecutor tp) { |
| parent = tp; |
| } |
| |
| public boolean force(Runnable o) { |
| if ( parent==null || parent.isShutdown() ) throw new RejectedExecutionException("Executor not running, can't force a command into the queue"); |
| return super.offer(o); //forces the item onto the queue, to be used if the task is rejected |
| } |
| |
| public boolean force(Runnable o, long timeout, TimeUnit unit) throws InterruptedException { |
| if ( parent==null || parent.isShutdown() ) throw new RejectedExecutionException("Executor not running, can't force a command into the queue"); |
| return super.offer(o,timeout,unit); //forces the item onto the queue, to be used if the task is rejected |
| } |
| |
| @Override |
| public boolean offer(Runnable o) { |
| //we can't do any checks |
| if (parent==null) return super.offer(o); |
| //we are maxed out on threads, simply queue the object |
| if (parent.getPoolSize() == parent.getMaximumPoolSize()) return super.offer(o); |
| //we have idle threads, just add it to the queue |
| if (parent.getSubmittedCount()<=(parent.getPoolSize())) return super.offer(o); |
| //if we have less threads than maximum force creation of a new thread |
| if (parent.getPoolSize()<parent.getMaximumPoolSize()) return false; |
| //if we reached here, we need to add it to the queue |
| return super.offer(o); |
| } |
| |
| |
| @Override |
| public Runnable poll(long timeout, TimeUnit unit) |
| throws InterruptedException { |
| Runnable runnable = super.poll(timeout, unit); |
| if (runnable == null && parent != null) { |
| // the poll timed out, it gives an opportunity to stop the current |
| // thread if needed to avoid memory leaks. |
| parent.stopCurrentThreadIfNeeded(); |
| } |
| return runnable; |
| } |
| |
| @Override |
| public Runnable take() throws InterruptedException { |
| if (parent != null && parent.currentThreadShouldBeStopped()) { |
| return poll(parent.getKeepAliveTime(TimeUnit.MILLISECONDS), |
| TimeUnit.MILLISECONDS); |
| // yes, this may return null (in case of timeout) which normally |
| // does not occur with take() |
| // but the ThreadPoolExecutor implementation allows this |
| } |
| return super.take(); |
| } |
| |
| @Override |
| public int remainingCapacity() { |
| if (forcedRemainingCapacity != null) { |
| // ThreadPoolExecutor.setCorePoolSize checks that |
| // remainingCapacity==0 to allow to interrupt idle threads |
| // I don't see why, but this hack allows to conform to this |
| // "requirement" |
| return forcedRemainingCapacity.intValue(); |
| } |
| return super.remainingCapacity(); |
| } |
| |
| public void setForcedRemainingCapacity(Integer forcedRemainingCapacity) { |
| this.forcedRemainingCapacity = forcedRemainingCapacity; |
| } |
| |
| } |