org.glassfish.grizzly.threadpool.QueueLimitedThreadPool Maven / Gradle / Ivy

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package org.glassfish.grizzly.threadpool;

import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.Semaphore;

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

    private final Semaphore queuePermits;

    /**
     * @param config the {@link ThreadPoolConfig} to configure this pool.
     */
    QueueLimitedThreadPool(ThreadPoolConfig config) {
        super(config);
        if (config.getQueueLimit() < 0) {
            throw new IllegalArgumentException("maxQueuedTasks < 0");
        }

        queuePermits = new Semaphore(config.getQueueLimit());
    }

    @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) {
            throw new RejectedExecutionException("ThreadPool is not running");
        }

        if (!queuePermits.tryAcquire()) {
            onTaskQueueOverflow();
        }

        if (!workQueue.offer(command)) {
            queuePermits.release();
            onTaskQueueOverflow();
        }

        onTaskQueued(command);
    }

    @Override
    protected final void beforeExecute(final Worker worker, final Thread t,
            final Runnable r) {
        super.beforeExecute(worker, t, r);
        queuePermits.release();
    }
}