QueueLimitedThreadPool.java

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package com.sun.grizzly.util;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Need to evaluate queuesize limit perf implications on this fixedpool variant.
 * The atomic counter can in theory approach synchronized (lack of) scalability
 * in heavy load situatuions.
 * 
 * @author gustav trede
 */
final class QueueLimitedThreadPool extends FixedThreadPool{

    private final int maxQueuedTasks;
    
    private final AtomicInteger queueSize = new AtomicInteger();

    /**
     * @param name
     * @param poolsize
     * @param threadFactory {@link ThreadFactory}
     * @param workQueue {@link BlockingQueue}
     * @param maxQueuedTasks 
     */
    QueueLimitedThreadPool(String name, int poolsize,int maxQueuedTasks,
            ThreadFactory threadFactory,BlockingQueue<Runnable> workQueue,
            ThreadPoolMonitoringProbe probe) {
        super(name,poolsize,workQueue,threadFactory,probe);
        if (maxQueuedTasks < 0)
            throw new IllegalArgumentException("maxQueuedTasks < 0");
        this.maxQueuedTasks = maxQueuedTasks;
    }

    @Override
    public final void execute(Runnable command) {
       if (command == null) { // must nullcheck to ensure queuesize is valid
            throw new IllegalArgumentException("Runnable task is null");
        }
        if (running){
            if (queueSize.incrementAndGet() <= maxQueuedTasks
                    && workQueue.offer(command)) {
                onTaskQueued(command);
                return;
            }
            onTaskQueueOverflow();
            return;
        }
        throw new RejectedExecutionException("ThreadPool is not running");
    }

    @Override
    protected void onTaskQueueOverflow() {
        queueSize.decrementAndGet();
        super.onTaskQueueOverflow();
    }

    @Override
    public int getQueueSize() {
        return queueSize.get();
    }

    @Override
    public int getMaxQueuedTasksCount() {
        return maxQueuedTasks;
    }

    @Override
    protected final void beforeExecute(Thread t, Runnable r) {
        super.beforeExecute(t, r);
        queueSize.decrementAndGet();        
    }

}