/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed 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.springframework.scheduling.concurrent;

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.TimeUnit;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.lang.Nullable;

A Spring FactoryBean that builds and exposes a preconfigured ForkJoinPool. 
Author:
Juergen Hoeller
Since:
3.1/**
 * A Spring {@link FactoryBean} that builds and exposes a preconfigured {@link ForkJoinPool}.
 *
 * @author Juergen Hoeller
 * @since 3.1
 */
public class ForkJoinPoolFactoryBean implements FactoryBean<ForkJoinPool>, InitializingBean, DisposableBean {

	private boolean commonPool = false;

	private int parallelism = Runtime.getRuntime().availableProcessors();

	private ForkJoinPool.ForkJoinWorkerThreadFactory threadFactory = ForkJoinPool.defaultForkJoinWorkerThreadFactory;

	@Nullable
	private Thread.UncaughtExceptionHandler uncaughtExceptionHandler;

	private boolean asyncMode = false;

	private int awaitTerminationSeconds = 0;

	@Nullable
	private ForkJoinPool forkJoinPool;


	
Set whether to expose JDK 8's 'common' ForkJoinPool. 
Default is "false", creating a local ForkJoinPool instance based on the "parallelism", "threadFactory", "uncaughtExceptionHandler" and "asyncMode" properties on this FactoryBean. 
NOTE: Setting this flag to "true" effectively ignores all other properties on this FactoryBean, reusing the shared common JDK ForkJoinPool instead. This is a fine choice on JDK 8 but does remove the application's ability to customize ForkJoinPool behavior, in particular the use of custom threads. 
See Also:
ForkJoinPool.commonPool()
Since:
3.2/**
	 * Set whether to expose JDK 8's 'common' {@link ForkJoinPool}.
	 * <p>Default is "false", creating a local {@link ForkJoinPool} instance based on the
	 * {@link #setParallelism "parallelism"}, {@link #setThreadFactory "threadFactory"},
	 * {@link #setUncaughtExceptionHandler "uncaughtExceptionHandler"} and
	 * {@link #setAsyncMode "asyncMode"} properties on this FactoryBean.
	 * <p><b>NOTE:</b> Setting this flag to "true" effectively ignores all other
	 * properties on this FactoryBean, reusing the shared common JDK {@link ForkJoinPool}
	 * instead. This is a fine choice on JDK 8 but does remove the application's ability
	 * to customize ForkJoinPool behavior, in particular the use of custom threads.
	 * @since 3.2
	 * @see java.util.concurrent.ForkJoinPool#commonPool()
	 */
	public void setCommonPool(boolean commonPool) {
		this.commonPool = commonPool;
	}

	
Specify the parallelism level. Default is Runtime.availableProcessors(). /**
	 * Specify the parallelism level. Default is {@link Runtime#availableProcessors()}.
	 */
	public void setParallelism(int parallelism) {
		this.parallelism = parallelism;
	}

	
Set the factory for creating new ForkJoinWorkerThreads. Default is ForkJoinPool.defaultForkJoinWorkerThreadFactory. /**
	 * Set the factory for creating new ForkJoinWorkerThreads.
	 * Default is {@link ForkJoinPool#defaultForkJoinWorkerThreadFactory}.
	 */
	public void setThreadFactory(ForkJoinPool.ForkJoinWorkerThreadFactory threadFactory) {
		this.threadFactory = threadFactory;
	}

	
Set the handler for internal worker threads that terminate due to unrecoverable errors
encountered while executing tasks. Default is none.
/**
	 * Set the handler for internal worker threads that terminate due to unrecoverable errors
	 * encountered while executing tasks. Default is none.
	 */
	public void setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler uncaughtExceptionHandler) {
		this.uncaughtExceptionHandler = uncaughtExceptionHandler;
	}

	
Specify whether to establish a local first-in-first-out scheduling mode for forked tasks that are never joined. This mode (asyncMode = true) may be more appropriate than the default locally stack-based mode in applications in which worker threads only process event-style asynchronous tasks. Default is false. /**
	 * Specify whether to establish a local first-in-first-out scheduling mode for forked tasks
	 * that are never joined. This mode (asyncMode = {@code true}) may be more appropriate
	 * than the default locally stack-based mode in applications in which worker threads only
	 * process event-style asynchronous tasks. Default is {@code false}.
	 */
	public void setAsyncMode(boolean asyncMode) {
		this.asyncMode = asyncMode;
	}

	
Set the maximum number of seconds that this ForkJoinPool is supposed to block
on shutdown in order to wait for remaining tasks to complete their execution
before the rest of the container continues to shut down. This is particularly
useful if your remaining tasks are likely to need access to other resources
that are also managed by the container.
By default, this ForkJoinPool won't wait for the termination of tasks at all.
It will continue to fully execute all ongoing tasks as well as all remaining
tasks in the queue, in parallel to the rest of the container shutting down.
In contrast, if you specify an await-termination period using this property,
this executor will wait for the given time (max) for the termination of tasks.
Note that this feature works for the "commonPool" mode as well. The underlying ForkJoinPool won't actually terminate in that case but will wait for all tasks to terminate. 
See Also:
ForkJoinPool.shutdown()
ForkJoinPool.awaitTermination/**
	 * Set the maximum number of seconds that this ForkJoinPool is supposed to block
	 * on shutdown in order to wait for remaining tasks to complete their execution
	 * before the rest of the container continues to shut down. This is particularly
	 * useful if your remaining tasks are likely to need access to other resources
	 * that are also managed by the container.
	 * <p>By default, this ForkJoinPool won't wait for the termination of tasks at all.
	 * It will continue to fully execute all ongoing tasks as well as all remaining
	 * tasks in the queue, in parallel to the rest of the container shutting down.
	 * In contrast, if you specify an await-termination period using this property,
	 * this executor will wait for the given time (max) for the termination of tasks.
	 * <p>Note that this feature works for the {@link #setCommonPool "commonPool"}
	 * mode as well. The underlying ForkJoinPool won't actually terminate in that
	 * case but will wait for all tasks to terminate.
	 * @see java.util.concurrent.ForkJoinPool#shutdown()
	 * @see java.util.concurrent.ForkJoinPool#awaitTermination
	 */
	public void setAwaitTerminationSeconds(int awaitTerminationSeconds) {
		this.awaitTerminationSeconds = awaitTerminationSeconds;
	}

	@Override
	public void afterPropertiesSet() {
		this.forkJoinPool = (this.commonPool ? ForkJoinPool.commonPool() :
				new ForkJoinPool(this.parallelism, this.threadFactory, this.uncaughtExceptionHandler, this.asyncMode));
	}


	@Override
	@Nullable
	public ForkJoinPool getObject() {
		return this.forkJoinPool;
	}

	@Override
	public Class<?> getObjectType() {
		return ForkJoinPool.class;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}


	@Override
	public void destroy() {
		if (this.forkJoinPool != null) {
			// Ignored for the common pool.
			this.forkJoinPool.shutdown();

			// Wait for all tasks to terminate - works for the common pool as well.
			if (this.awaitTerminationSeconds > 0) {
				try {
					this.forkJoinPool.awaitTermination(this.awaitTerminationSeconds, TimeUnit.SECONDS);
				}
				catch (InterruptedException ex) {
					Thread.currentThread().interrupt();
				}
			}
		}
	}

}