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Mica net is a net framework.
There is a newer version: 1.0.8
/**
 * 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.tio.utils.timer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.*;
import java.util.concurrent.atomic.LongAdder;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.Consumer;

/**
 * SystemTimer
 *
 * @author kafka、guest、L.cm
 */
public class SystemTimer implements Timer, Consumer {
	private static final Logger logger = LoggerFactory.getLogger(SystemTimer.class);
	/**
	 * 任务执行线程
	 */
	private final ExecutorService taskExecutor;
	/**
	 * 一个Timer只有一个delayQueue
	 */
	private final DelayQueue delayQueue = new DelayQueue<>();
	/**
	 * 任务计数器
	 */
	private final LongAdder taskCounter = new LongAdder();
	/**
	 * 底层时间轮
	 */
	private final TimingWheel timingWheel;

	/**
	 * Locks used to protect data structures while ticking
	 */
	private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();

	private final ReentrantReadWriteLock.ReadLock readLock = readWriteLock.readLock();

	private final ReentrantReadWriteLock.WriteLock writeLock = readWriteLock.writeLock();

	public SystemTimer() {
		this("SystemTimerExecutor");
	}

	public SystemTimer(String executeName) {
		this(1L, 20, executeName);
	}

	public SystemTimer(long tickMs, int wheelSize, String executeName) {
		this(tickMs, wheelSize, Timer.getHiresClockMs(), executeName);
	}

	public SystemTimer(long tickMs, int wheelSize, long startMs, String executeName) {
		taskExecutor = new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS,
			new LinkedBlockingQueue<>(Integer.MAX_VALUE), r -> new Thread(r, executeName));
		timingWheel = new TimingWheel(tickMs, wheelSize, startMs, taskCounter, delayQueue);
	}

	@Override
	public void add(TimerTask timerTask) {
		readLock.lock();
		try {
			// 通过任务的延时加上当前时间得到延时的具体时刻，作为定时任务的过期时间
			addTimerTaskEntry(new TimerTaskEntry(timerTask, timerTask.getDelayMs() + Timer.getHiresClockMs()));
		} finally {
			readLock.unlock();
		}
	}

	@Override
	public boolean advanceClock(long timeoutMs) {
		TimerTaskList bucket;
		try {
			bucket = delayQueue.poll(timeoutMs, TimeUnit.MILLISECONDS);
		} catch (InterruptedException e) {
			Thread.currentThread().interrupt();
			logger.error(e.getMessage(), e);
			return false;
		}
		if (bucket == null) {
			return false;
		}
		writeLock.lock();
		try {
			while (bucket != null) {
				// 推进时间
				timingWheel.advanceClock(bucket.getExpiration());
				// 执行过期任务（包含降级操作）
				bucket.flush(this);
				bucket = delayQueue.poll();
			}
		} finally {
			writeLock.unlock();
		}
		return true;
	}

	@Override
	public long size() {
		return taskCounter.sum();
	}

	@Override
	public void shutdown() {
		try {
			taskExecutor.shutdown();
		} catch (Exception e1) {
			logger.error(e1.getMessage(), e1);
		}
		try {
			taskExecutor.awaitTermination(6000, TimeUnit.SECONDS);
		} catch (InterruptedException e) {
			Thread.currentThread().interrupt();
			logger.error(e.getMessage(), e);
		}
	}

	private void addTimerTaskEntry(TimerTaskEntry timerTaskEntry) {
		// 尝试将任务加入时间轮
		if (!timingWheel.add(timerTaskEntry)) {
			// 任务过期则执行任务，仅当 任务已经过期 或者 任务主动取消 才会进入此分支
			if (!timerTaskEntry.cancelled()) {
				taskExecutor.submit(timerTaskEntry.getTimerTask());
			}
		}
	}

	/**
	 * Applies this function to the given argument.
	 *
	 * @param timerTaskEntry the function argument
	 */
	@Override
	public void accept(TimerTaskEntry timerTaskEntry) {
		addTimerTaskEntry(timerTaskEntry);
	}
}