/*
 * Copyright (c) 2015, 2019 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.jersey.spi;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import javax.annotation.PreDestroy;

Default implementation of the Jersey executor service provider SPI. 
 This provider creates and provisions a shared ThreadPoolExecutor instance using the customizable values for : 

number of core pool threads
maximum number of threads in the pool
thread keep-alive time (in seconds)
backing thread pool work queue
backing thread factory
rejected task handler

Subclasses may override the respective methods to customize the parameters of the provisioned thread pool executor.

Author:
Marek Potociar
Since:
2.18/**
 * Default implementation of the Jersey {@link org.glassfish.jersey.spi.ExecutorServiceProvider executor service provider SPI}.
 * <p>
 * This provider creates and provisions a shared {@link java.util.concurrent.ThreadPoolExecutor} instance
 * using the customizable values for :
 * <ul>
 * <li>{@link #getCorePoolSize() number of core pool threads}</li>
 * <li>{@link #getMaximumPoolSize() maximum number of threads in the pool}</li>
 * <li>{@link #getKeepAliveTime() thread keep-alive time (in seconds)}</li>
 * <li>{@link #getWorkQueue() backing thread pool work queue}</li>
 * <li>{@link #getBackingThreadFactory() backing thread factory}</li>
 * <li>{@link #getRejectedExecutionHandler() rejected task handler}</li>
 * </ul>
 * Subclasses may override the respective methods to customize the parameters of the provisioned thread pool executor.
 * </p>
 *
 * @author Marek Potociar
 * @since 2.18
 */
public class ThreadPoolExecutorProvider extends AbstractThreadPoolProvider<ThreadPoolExecutor>
        implements ExecutorServiceProvider {

    private static final long CACHED_POOL_KEEP_ALIVE_DEFAULT_TIMEOUT = 60L;

    
Create a new instance of the thread pool executor provider.
Params:
name – provider name. The name will be used to name the threads created & used by the
            provisioned thread pool executor./**
     * Create a new instance of the thread pool executor provider.
     *
     * @param name provider name. The name will be used to name the threads created & used by the
     *             provisioned thread pool executor.
     */
    public ThreadPoolExecutorProvider(final String name) {
        super(name);
    }

    @Override
    public ExecutorService getExecutorService() {
        return super.getExecutor();
    }

    @Override
    protected final ThreadPoolExecutor createExecutor(
            final int corePoolSize, final ThreadFactory threadFactory, final RejectedExecutionHandler handler) {
        return createExecutor(
                corePoolSize,
                getMaximumPoolSize(),
                getKeepAliveTime(),
                getWorkQueue(),
                threadFactory,
                handler);
    }

    
Creates a new ThreadPoolExecutor with the given initial parameters. 
Params:
corePoolSize –    the number of threads to keep in the thread pool, even if they are idle.
maximumPoolSize – the maximum number of threads to allow in the thread pool.
keepAliveTime –   when the number of threads is greater than the core, this is the maximum time (in seconds)
                       that excess idle threads will wait for new tasks before terminating.
workQueue –  the queue to use for holding tasks before they are executed. This queue will hold only the Runnable tasks submitted by the execute method.
threadFactory –   the factory to use when the executor creates a new thread.
handler –         the handler to use when execution is blocked because the thread bounds and queue capacities
                       are reached.
Throws:
IllegalArgumentException – if one of the following holds:
 corePoolSize < 0
 keepAliveTime < 0
 maximumPoolSize <= 0
 maximumPoolSize < corePoolSize
NullPointerException –  if workQueue or threadFactory or handler is null.
Returns:
new configured thread pool instance./**
     * Creates a new {@code ThreadPoolExecutor} with the given initial parameters.
     *
     * @param corePoolSize    the number of threads to keep in the thread pool, even if they are idle.
     * @param maximumPoolSize the maximum number of threads to allow in the thread pool.
     * @param keepAliveTime   when the number of threads is greater than the core, this is the maximum time (in seconds)
     *                        that excess idle threads will wait for new tasks before terminating.
     * @param workQueue       the queue to use for holding tasks before they are executed.  This queue will hold only the
     *                        {@code Runnable} tasks submitted by the {@code execute} method.
     * @param threadFactory   the factory to use when the executor creates a new thread.
     * @param handler         the handler to use when execution is blocked because the thread bounds and queue capacities
     *                        are reached.
     * @return new configured thread pool instance.
     * @throws IllegalArgumentException if one of the following holds:<br>
     *                                  {@code corePoolSize < 0}<br>
     *                                  {@code keepAliveTime < 0}<br>
     *                                  {@code maximumPoolSize <= 0}<br>
     *                                  {@code maximumPoolSize < corePoolSize}
     * @throws NullPointerException     if {@code workQueue} or {@code threadFactory} or {@code handler} is {@code null}.
     */
    protected ThreadPoolExecutor createExecutor(
            final int corePoolSize,
            final int maximumPoolSize,
            final long keepAliveTime,
            final BlockingQueue<Runnable> workQueue,
            final ThreadFactory threadFactory,
            final RejectedExecutionHandler handler) {

        return new ThreadPoolExecutor(
                corePoolSize,
                maximumPoolSize,
                keepAliveTime,
                TimeUnit.SECONDS,
                workQueue,
                threadFactory,
                handler);
    }

    
Get the maximum number of threads to allow in the thread pool.
 The value from this method is passed as one of the input parameters in a call to the createExecutor(int, int, long, BlockingQueue<Runnable>, ThreadFactory, RejectedExecutionHandler) method. 
 The method can be overridden to customize the maximum number of threads allowed in the provisioned thread pool executor. If not customized, the method defaults to Integer.MAX_VALUE. 
Returns:
maximum number of threads allowed in the thread pool./**
     * Get the maximum number of threads to allow in the thread pool.
     * <p>
     * The value from this method is passed as one of the input parameters in a call to the
     * {@link #createExecutor(int, int, long, java.util.concurrent.BlockingQueue, java.util.concurrent.ThreadFactory,
     * java.util.concurrent.RejectedExecutionHandler)} method.
     * </p>
     * <p>
     * The method can be overridden to customize the maximum number of threads allowed in the provisioned thread pool executor.
     * If not customized, the method defaults to {@link java.lang.Integer#MAX_VALUE}.
     * </p>
     *
     * @return maximum number of threads allowed in the thread pool.
     */
    protected int getMaximumPoolSize() {
        return Integer.MAX_VALUE;
    }

    
Get the thread keep-alive time (in seconds).

When the number of threads in the provisioned thread pool is greater than the core, this is the maximum time (in seconds)
that excess idle threads will wait for new tasks before terminating.

 The value from this method is passed as one of the input parameters in a call to the createExecutor(int, int, long, BlockingQueue<Runnable>, ThreadFactory, RejectedExecutionHandler) method. 

The method can be overridden to customize the thread keep-alive time in the provisioned thread pool executor.
If not customized, the method defaults to:

60 in case the maximum pool size is equal to Integer.MAX_VALUE
0L in case the maximum pool size is lower than java.lang.Integer#MAX_VALUE
 The default value computation closely corresponds to the thread pool executor configurations used in Executors.newCachedThreadPool() and Executors.newFixedThreadPool(int) methods. 

Returns:
thread keep-alive time (in seconds) for the provisioned thread pool executor./**
     * Get the thread keep-alive time (in seconds).
     * <p>
     * When the number of threads in the provisioned thread pool is greater than the core, this is the maximum time (in seconds)
     * that excess idle threads will wait for new tasks before terminating.
     * </p>
     * <p>
     * The value from this method is passed as one of the input parameters in a call to the
     * {@link #createExecutor(int, int, long, java.util.concurrent.BlockingQueue, java.util.concurrent.ThreadFactory,
     * java.util.concurrent.RejectedExecutionHandler)} method.
     * </p>
     * <p>
     * The method can be overridden to customize the thread keep-alive time in the provisioned thread pool executor.
     * If not customized, the method defaults to:
     * <ul>
     * <li>{@value #CACHED_POOL_KEEP_ALIVE_DEFAULT_TIMEOUT} in case the {@link #getMaximumPoolSize() maximum pool size}
     * is equal to {@link java.lang.Integer#MAX_VALUE}</li>
     * <li>{@code 0L} in case the maximum pool size is lower than
     * {@code java.lang.Integer#MAX_VALUE}</li>
     * </ul>
     * The default value computation closely corresponds to the thread pool executor configurations used in
     * {@link java.util.concurrent.Executors#newCachedThreadPool()} and
     * {@link java.util.concurrent.Executors#newFixedThreadPool(int)} methods.
     * </p>
     *
     * @return thread keep-alive time (in seconds) for the provisioned thread pool executor.
     */
    protected long getKeepAliveTime() {
        return CACHED_POOL_KEEP_ALIVE_DEFAULT_TIMEOUT;
    }

    
Get the work queue for the provisioned thread pool executor.
 The work queue is used to hold the tasks before they are executed by the provisioned thread pool executor. The queue will hold only the Runnable tasks submitted by the ThreadPoolExecutor.execute method. 
 The value from this method is passed as one of the input parameters in a call to the createExecutor(int, int, long, BlockingQueue<Runnable>, ThreadFactory, RejectedExecutionHandler) method. 

The method can be overridden to customize the work queue used by the provisioned thread pool executor.
If not customized, the method defaults to:

SynchronousQueue in case the maximum pool size is equal to Integer.MAX_VALUE
LinkedBlockingQueue in case the maximum pool size is lower than java.lang.Integer#MAX_VALUE
 The default value computation closely corresponds to the thread pool executor configurations used in Executors.newCachedThreadPool() and Executors.newFixedThreadPool(int) methods. 

Returns:
work queue for the provisioned thread pool executor./**
     * Get the work queue for the provisioned thread pool executor.
     * <p>
     * The work queue is used to hold the tasks before they are executed by the provisioned thread pool executor.
     * The queue will hold only the {@link Runnable} tasks submitted by the {@link ThreadPoolExecutor#execute} method.
     * </p>
     * <p>
     * The value from this method is passed as one of the input parameters in a call to the
     * {@link #createExecutor(int, int, long, java.util.concurrent.BlockingQueue, java.util.concurrent.ThreadFactory,
     * java.util.concurrent.RejectedExecutionHandler)} method.
     * </p>
     * <p>
     * The method can be overridden to customize the work queue used by the provisioned thread pool executor.
     * If not customized, the method defaults to:
     * <ul>
     * <li>{@link java.util.concurrent.SynchronousQueue} in case the {@link #getMaximumPoolSize() maximum pool size}
     * is equal to {@link java.lang.Integer#MAX_VALUE}</li>
     * <li>{@link java.util.concurrent.LinkedBlockingQueue} in case the maximum pool size is lower than
     * {@code java.lang.Integer#MAX_VALUE}</li>
     * </ul>
     * The default value computation closely corresponds to the thread pool executor configurations used in
     * {@link java.util.concurrent.Executors#newCachedThreadPool()} and
     * {@link java.util.concurrent.Executors#newFixedThreadPool(int)} methods.
     * </p>
     *
     * @return work queue for the provisioned thread pool executor.
     */
    protected BlockingQueue<Runnable> getWorkQueue() {
        return (getMaximumPoolSize() == Integer.MAX_VALUE)
                ? new SynchronousQueue<Runnable>() : new LinkedBlockingQueue<Runnable>();
    }

    @Override
    public void dispose(final ExecutorService executorService) {
        // NO-OP.
    }

    
Container pre-destroy handler method.
 Invoking the method closes this provider. 
/**
     * Container pre-destroy handler method.
     * <p>
     * Invoking the method {@link #close() closes} this provider.
     * </p>
     */
    @PreDestroy
    public void preDestroy() {
        close();
    }
}