/*
* 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.catalina.tribes.transport;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
* A very simple thread pool class. The pool size is set at construction time and remains fixed. Threads are cycled
* through a FIFO idle queue.
*/
public class RxTaskPool {
final List<AbstractRxTask> idle = new ArrayList<>();
final List<AbstractRxTask> used = new ArrayList<>();
final Object mutex = new Object();
boolean running = true;
private int maxTasks;
private int minTasks;
private final TaskCreator creator;
public RxTaskPool(int maxTasks, int minTasks, TaskCreator creator) throws Exception {
// fill up the pool with worker threads
this.maxTasks = maxTasks;
this.minTasks = minTasks;
this.creator = creator;
}
protected void configureTask(AbstractRxTask task) {
synchronized (task) {
task.setTaskPool(this);
}
}
/**
* Find an idle worker thread, if any. Could return null.
*
* @return a worker
*/
public AbstractRxTask getRxTask() {
AbstractRxTask worker = null;
synchronized (mutex) {
while (worker == null && running) {
if (!idle.isEmpty()) {
try {
worker = idle.remove(0);
} catch (java.util.NoSuchElementException ignore) {
// Should never happen as access to idle is always synchronized on mutex
}
} else if (used.size() < this.maxTasks && creator != null) {
worker = creator.createRxTask();
configureTask(worker);
} else {
try {
mutex.wait();
} catch (InterruptedException x) {
Thread.currentThread().interrupt();
}
}
}
if (worker != null) {
used.add(worker);
}
}
return worker;
}
public int available() {
synchronized (mutex) {
return idle.size();
}
}
/**
* Called by the worker thread to return itself to the idle pool.
*
* @param worker The worker
*/
public void returnWorker(AbstractRxTask worker) {
if (running) {
synchronized (mutex) {
used.remove(worker);
if (idle.size() < maxTasks && !idle.contains(worker)) {
idle.add(worker); // let max be the upper limit
} else {
worker.close();
}
mutex.notifyAll();
}
} else {
worker.close();
}
}
public int getMaxThreads() {
return maxTasks;
}
public int getMinThreads() {
return minTasks;
}
public void stop() {
running = false;
synchronized (mutex) {
Iterator<AbstractRxTask> i = idle.iterator();
while (i.hasNext()) {
AbstractRxTask worker = i.next();
returnWorker(worker);
i.remove();
}
}
}
public void setMaxTasks(int maxThreads) {
this.maxTasks = maxThreads;
}
public void setMinTasks(int minThreads) {
this.minTasks = minThreads;
}
public TaskCreator getTaskCreator() {
return this.creator;
}
public interface TaskCreator {
AbstractRxTask createRxTask();
}
}