详细内容
详细内容大概分为4个部分，1.应用场景 2.遇到问题 3.设计 4.实现 5.运行效果
1.应用场景
需要定时推送数据，且轻量化的实现。
2.遇到问题
- 如果启动一个定时器去定时轮询
- （1）轮询效率比较低
- （2）每次扫库，已经被执行过记录，仍然会被扫描（只是不会出现在结果集中），会做重复工作
- （3）时效性不够好，如果每小时轮询一次，最差的情况下会有时间误差
- 如何利用“延时消息”，对于每个任务只触发一次，保证效率的同时保证实时性，是今天要讨论的问题。
3.设计
高效延时消息，包含两个重要的数据结构：
- 环形队列，例如可以创建一个包含3600个slot的环形队列（本质是个数组）
- 任务集合，环上每一个slot是一个Set
同时，启动一个timer，这个timer每隔1s，在上述环形队列中移动一格，有一个Current Index指针来标识正在检测的slot。
Task结构中有两个很重要的属性：
- Cycle-Num：当Current Index第几圈扫描到这个Slot时，执行任务
- Task-Function：需要执行的任务指针
假设当前Current Index指向第一格，当有延时消息到达之后，例如希望3610秒之后，触发一个延时消息任务，只需：
- 计算这个Task应该放在哪一个slot，现在指向1，3610秒之后，应该是第11格，所以这个Task应该放在第11个slot的Set中
- 计算这个Task的Cycle-Num，由于环形队列是3600格（每秒移动一格，正好1小时），这个任务是3610秒后执行，所以应该绕3610/3600=1圈之后再执行，于是Cycle-Num=1
Current Index不停的移动，每秒移动到一个新slot，这个slot中对应的Set，每个Task看Cycle-Num是不是0：
- 如果不是0，说明还需要多移动几圈，将Cycle-Num减1
- 如果是0，说明马上要执行这个Task了，取出Task-Funciton执行（可以用单独的线程来执行Task），并把这个Task从Set中删除
使用了“延时消息”方案之后，“订单48小时后关闭评价”的需求，只需将在订单关闭时，触发一个48小时之后的延时消息即可：
- 无需再轮询全部订单，效率高
- 一个订单，任务只执行一次
- 时效性好，精确到秒（控制timer移动频率可以控制精度）
4.实现
首先写一个方案要理清楚自己的项目结构，我做了如下分层。
Interfaces ， 这层里主要约束延迟消息队列的队列和消息任务行。
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public interface IRingQueue<T>{ /// <summary> /// Add tasks [add tasks will automatically generate: task Id, task slot location, number of task cycles] /// </summary> /// <param name="delayTime">The specified task is executed after N seconds.</param> /// <param name="action">Definitions of callback</param> void Add(long delayTime,Action<T> action); /// <summary> /// Add tasks [add tasks will automatically generate: task Id, task slot location, number of task cycles] /// </summary> /// <param name="delayTime">The specified task is executed after N seconds.</param> /// <param name="action">Definitions of callback.</param> /// <param name="data">Parameters used in the callback function.</param> void Add(long delayTime, Action<T> action, T data); /// <summary> /// Add tasks [add tasks will automatically generate: task Id, task slot location, number of task cycles] /// </summary> /// <param name="delayTime"></param> /// <param name="action">Definitions of callback</param> /// <param name="data">Parameters used in the callback function.</param> /// <param name="id">Task ID, used when deleting tasks.</param> void Add(long delayTime, Action<T> action, T data, long id); /// <summary> /// Remove tasks [need to know: where the task is, which specific task]. /// </summary> /// <param name="index">Task slot location</param> /// <param name="id">Task ID, used when deleting tasks.</param> void Remove(long id); /// <summary> /// Launch queue. /// </summary> void Start();} public interface ITask { } |
Achieves，这层里实现之前定义的接口，这里写成抽象类是为了后面方便扩展。
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using System;using System.Collections.Concurrent;using System.Linq;using System.Threading;using System.Threading.Tasks;using DelayMessageApp.Interfaces;namespace DelayMessageApp.Achieves.Base{public abstract class BaseQueue<T> : IRingQueue<T>{ private long _pointer = 0L; private ConcurrentBag<BaseTask<T>>[] _arraySlot; private int ArrayMax; /// <summary> /// Ring queue. /// </summary> public ConcurrentBag<BaseTask<T>>[] ArraySlot { get { return _arraySlot ?? (_arraySlot = new ConcurrentBag<BaseTask<T>>[ArrayMax]); } } public BaseQueue(int arrayMax) { if (arrayMax < 60 && arrayMax % 60 == 0) throw new Exception("Ring queue length cannot be less than 60 and is a multiple of 60 ."); ArrayMax = arrayMax; } public void Add(long delayTime, Action<T> action) { Add(delayTime, action, default(T)); } public void Add(long delayTime,Action<T> action,T data) { Add(delayTime, action, data,0); } public void Add(long delayTime, Action<T> action, T data,long id) { NextSlot(delayTime, out long cycle, out long pointer); ArraySlot[pointer] = ArraySlot[pointer] ?? (ArraySlot[pointer] = new ConcurrentBag<BaseTask<T>>()); var baseTask = new BaseTask<T>(cycle, action, data,id); ArraySlot[pointer].Add(baseTask); } /// <summary> /// Remove tasks based on ID. /// </summary> /// <param name="id"></param> public void Remove(long id) { try { Parallel.ForEach(ArraySlot, (ConcurrentBag<BaseTask<T>> collection, ParallelLoopState state) => { var resulTask = collection.FirstOrDefault(p => p.Id == id); if (resulTask != null) { collection.TryTake(out resulTask); state.Break(); } }); } catch (Exception e) { Console.WriteLine(e); } } public void Start() { while (true) { RightMovePointer(); Thread.Sleep(1000); Console.WriteLine(DateTime.Now.ToString()); } } /// <summary> /// Calculate the information of the next slot. /// </summary> /// <param name="delayTime">Delayed execution time.</param> /// <param name="cycle">Number of turns.</param> /// <param name="index">Task location.</param> private void NextSlot(long delayTime, out long cycle,out long index) { try { var circle = delayTime / ArrayMax; var second = delayTime % ArrayMax; var current_pointer = GetPointer(); var queue_index = 0L; if (delayTime - ArrayMax > ArrayMax) { circle = 1; } else if (second > ArrayMax) { circle += 1; } if (delayTime - circle * ArrayMax < ArrayMax) { second = delayTime - circle * ArrayMax; } if (current_pointer + delayTime >= ArrayMax) { cycle = (int)((current_pointer + delayTime) / ArrayMax); if (current_pointer + second - ArrayMax < 0) { queue_index = current_pointer + second; } else if (current_pointer + second - ArrayMax > 0) { queue_index = current_pointer + second - ArrayMax; } } else { cycle = 0; queue_index = current_pointer + second; } index = queue_index; } catch (Exception e) { Console.WriteLine(e); throw; } } /// <summary> /// Get the current location of the pointer. /// </summary> /// <returns></returns> private long GetPointer() { return Interlocked.Read(ref _pointer); } /// <summary> /// Reset pointer position. /// </summary> private void ReSetPointer() { Interlocked.Exchange(ref _pointer, 0); } /// <summary> /// Pointer moves clockwise. /// </summary> private void RightMovePointer() { try { if (GetPointer() >= ArrayMax - 1) { ReSetPointer(); } else { Interlocked.Increment(ref _pointer); } var pointer = GetPointer(); var taskCollection = ArraySlot[pointer]; if (taskCollection == null || taskCollection.Count == 0) return; Parallel.ForEach(taskCollection, (BaseTask<T> task) => { if (task.Cycle > 0) { task.SubCycleNumber(); } if (task.Cycle <= 0) { taskCollection.TryTake(out task); task.TaskAction(task.Data); } }); } catch (Exception e) { Console.WriteLine(e); throw; } }}}using System;using System.Threading;using DelayMessageApp.Interfaces;namespace DelayMessageApp.Achieves.Base{public class BaseTask<T> : ITask{ private long _cycle; private long _id; private T _data; public Action<T> TaskAction { get; set; } public long Cycle { get { return Interlocked.Read(ref _cycle); } set { Interlocked.Exchange(ref _cycle, value); } } public long Id { get { return _id; } set { _id = value; } } public T Data { get { return _data; } set { _data = value; } } public BaseTask(long cycle, Action<T> action, T data,long id) { Cycle = cycle; TaskAction = action; Data = data; Id = id; } public BaseTask(long cycle, Action<T> action,T data) { Cycle = cycle; TaskAction = action; Data = data; } public BaseTask(long cycle, Action<T> action) { Cycle = cycle; TaskAction = action; } public void SubCycleNumber() { Interlocked.Decrement(ref _cycle); }}} |
Logic，这层主要实现调用逻辑，调用者最终只需要关心把任务放进队列并指定什么时候执行就行了，根本不需要关心其它的任何信息。
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public static void Start(){ //1.Initialize queues of different granularity. IRingQueue<NewsModel> minuteRingQueue = new MinuteQueue<NewsModel>(); //2.Open thread. var lstTasks = new List<Task> { Task.Factory.StartNew(minuteRingQueue.Start) }; //3.Add tasks performed in different periods. minuteRingQueue.Add(5, new Action<NewsModel>((NewsModel newsObj) => { Console.WriteLine(newsObj.News); }), new NewsModel() { News = "Trump's visit to China！" }); minuteRingQueue.Add(10, new Action<NewsModel>((NewsModel newsObj) => { Console.WriteLine(newsObj.News); }), new NewsModel() { News = "Putin Pu's visit to China！" }); minuteRingQueue.Add(60, new Action<NewsModel>((NewsModel newsObj) => { Console.WriteLine(newsObj.News); }), new NewsModel() { News = "Eisenhower's visit to China！" }); minuteRingQueue.Add(120, new Action<NewsModel>((NewsModel newsObj) => { Console.WriteLine(newsObj.News); }), new NewsModel() { News = "Xi Jinping's visit to the US！" }); //3.Waiting for all tasks to complete is usually not completed. Because there is an infinite loop. //F5 Run the program and see the effect. Task.WaitAll(lstTasks.ToArray()); Console.Read();} |
Models，这层就是用来在延迟任务中带入的数据模型类而已了。自己用的时候换成任意自定义类型都可以。
5.运行效果
到此这篇关于如何实现定时推送的具体方案的文章就介绍到这了,希望对大家有所帮助,更多相关C#内容请搜索服务器之家以前的文章或继续浏览下面的相关文章，希望大家以后多多支持服务器之家！
原文链接：https://www.cnblogs.com/justzhuzhu/p/14669109.html
