Lazy Scheduler：我的轻量级任务调度框架

一、背景

工作中经常涉及任务调度，一直都是采用while(true) => if hitted DO => Thread.Sleep(interval)的模式。但是最近实在是感觉这种实现模式很挫。并且没有考虑到性能问题，需要撞击n次才能命中一次，使用效率不足5%（一百次while循环命中不到5次），但是单方面加大线程睡眠时间又无法保证高准确性和高精度。那有么有其它好的思路：即可以保持高准确性、高精度，又不浪费资源呢？

二、我的思路

上述的短板在于：无目的的线程Sleep，如果我们可以每次恰到好处的Sleep，即线程被唤醒后刚好赶上下一次的任务到来，命中率就是100%了嘛。所以可以这样做：进入While后先按照Scheduler计算出下次的运行时间距离现在还有多久(Interval)，然后直接Sleep(Interval)，等待线程唤醒后就立即执行下一个既定Task就可以了。那这样做唯一的难点就在于你的Scheduler是否可计算、是否可以计算出下一次的运行时间点。

还好，我碰到的逻辑都还是满足这一点需求的：

（1）每隔一段时间执行一次的计划任务；

（2）在指定时间点必须执行的计划任务;

其他人性化设定：周六周日不运行。

三、代码实现

（1）主要有：负责调度的接口：IScheduler；Scheduler设定:ISchedulerSetting;任务接口：ITask以及一些其他的辅助类。

（2）难点:计算Interval的实现类：FixTimeSchedulerSetting.cs和IntervalSchedulerSetting.cs

//Author:      night-king
// Email:       deepleo@163.com
//Home:       http://deepleo.com
//Github:     https://github.com/night-king/
//Date:         2013-11-1 
//Place:        Wuhan@China

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

namespace Deepleo.LazyScheduler.Setting
{
    public class FixTimeSchedulerSetting : IFixTimeSchedulerSetting, IWeekSchedulerSetting
    {
        public IList<DayOfWeek> ExcludeWeeks
        {
            get;
            set;
        }

        public int Hour
        {
            get;
            set;
        }

        public int Minutes
        {
            get;
            set;
        }

        public int Second
        {
            get;
            set;
        }

        public FixTimeSchedulerSetting(IList<DayOfWeek> excludeWeeks)
        {
            ExcludeWeeks = excludeWeeks;
        }

        public virtual TimeSpan CalculateNext()
        {
            var nowDateTime = System.DateTime.Now;
            var expectNextTime = System.DateTime.Parse(string.Format("{0}-{1}-{2} {3}:{4}:{5}", nowDateTime.Year, nowDateTime.Month, nowDateTime.Day, Hour, Minutes, Second));
            var todayWeek = nowDateTime.DayOfWeek;
            var km = new WeekManager(ExcludeWeeks);
            var delayDays = km.CalculateDelayDays(todayWeek);
            if (delayDays == 0)// this day of week can do
            {
                if (expectNextTime > nowDateTime) return expectNextTime - nowDateTime;
                else delayDays++;
            }
            return expectNextTime.AddDays(delayDays) - nowDateTime;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace Deepleo.LazyScheduler.Setting
{
    public class IntervalSchedulerSetting : IIntervalSchedulerSetting, IWeekSchedulerSetting
    {

        public TimeSpan Interval
        {
            get;
            set;
        }

        public IList<DayOfWeek> ExcludeWeeks
        {
            get;
            set;
        }

        public IntervalSchedulerSetting(IList<DayOfWeek> excludeWeeks)
        {
            ExcludeWeeks = excludeWeeks;
        }

        public TimeSpan CalculateNext()
        {
            var nowDateTime = System.DateTime.Now;
            var todayWeek =nowDateTime.DayOfWeek;
            var km = new WeekManager(ExcludeWeeks);
            var delayDays = km.CalculateDelayDays(todayWeek);
            var interval = Interval.Add(new TimeSpan(delayDays, 0, 0, 0));
            if (interval.CompareTo(new TimeSpan(0, 0, 1)) <= 0) return new TimeSpan(0, 0, 1);
            else return interval;
        }
    }
}

重要的辅助类：WeekManager的实现代码：

//Author:      night-king
// Email:       deepleo@163.com
//Home:       http://deepleo.com
//Github:     https://github.com/night-king/
//Date:         2013-11-1 
//Place:        Wuhan@China

using System;
using System.Collections.Generic;
using System.Text;

namespace Deepleo.LazyScheduler.Setting
{
 
    public class WeekManager
    {
        private Dictionary<int, DayOfWeek> _allowWeekDict;

        public WeekManager(IList<DayOfWeek> notAllowWeeks)
        {
            _allowWeekDict = new Dictionary<int, DayOfWeek>();
            if (!notAllowWeeks.Contains(DayOfWeek.Sunday))
                _allowWeekDict.Add(0, DayOfWeek.Sunday);
            if (!notAllowWeeks.Contains(DayOfWeek.Monday))
                _allowWeekDict.Add(1, DayOfWeek.Monday);
            if (!notAllowWeeks.Contains(DayOfWeek.Tuesday))
                _allowWeekDict.Add(2, DayOfWeek.Tuesday);
            if (!notAllowWeeks.Contains(DayOfWeek.Wednesday))
                _allowWeekDict.Add(3, DayOfWeek.Wednesday);
            if (!notAllowWeeks.Contains(DayOfWeek.Thursday))
                _allowWeekDict.Add(4, DayOfWeek.Thursday);
            if (!notAllowWeeks.Contains(DayOfWeek.Friday))
                _allowWeekDict.Add(5, DayOfWeek.Friday);
            if (!notAllowWeeks.Contains(DayOfWeek.Saturday))
                _allowWeekDict.Add(6, DayOfWeek.Saturday);
        }

        /// <summary>
        /// Calcute how many delay days
        /// </summary>
        /// <param name="week">current day of week</param>
        /// <returns>delay days</returns>
        public int CalculateDelayDays(DayOfWeek week)
        {
            var weekOfDay = (int)week;
            int distence = 0;
            while (true)
            {
                if (_allowWeekDict.ContainsKey(weekOfDay))
                {
                    return distence;
                }
                else
                {
                    weekOfDay = weekOfDay < 6 ? weekOfDay + 1 : 0;
                    distence++;
                }
            }
        }
    }
}

四、测试

(1)5s钟时间间隔的测试结果：