Net线程池设计
功能描述：
- 支持创建多个线程池，并统一管理
- 支持不同线程池的容量控制，以及最少活动线程的设置
- 支持不同线程池中活动线程的闲时设置，即线程空闲时间到期后即自动被回收
结构设计：
- ThreadWorkerPoolManager: 线程池管理器，用于统一创建，获取，销毁线程池，使用单例模式
- ThreadWorkerPool: 线程池，用于管理指定数量的线程，由ThreadWorkerPoolManager管理，自身无法创建与销毁
- TheadWorkerPoolItem: 线程池项，用于包装线程工作器，协助ThreadWorkerPool更好的管理线程，例如取出，放回，闲时的控制
- TheadWorker: 线程工作器，用于包装系统线程System.Threading.Thread，使其可以重复使用，减少Thrad创建和销毁的性能开销
结构关系图：
详细设计：
ThreadWoker
要点设计：
- 完成一次任务后，System.Threading.Thread不能被系统销毁, 默认情况下new Thread(ThreadStart start).Start(), 当ThreadStart委托的任务完成后，系统将销毁该线程，也就是说创建一个System.Threading.Thread实例只能使用一次；为了使线程能被重复使用，ThreadWoker将使用 while+sleeping 的方式对系统线程进行包装，同时使用AutoResetEvent代替Thread.Sleep(timeout)来达到更佳的控制
- 闲时设计，线程资源是极其宝贵的系统资源，如果线程池中存在大量的空闲线程这是一种浪费，极端情况下将影响系统的稳定性和工作效率；ThreadWorker将使用AutoResetEvent和事件通知的方式来代替在线程池中定期轮询检查的方式，每完成一个任务将重新开始空闲时间的计算，如果ThreadWorker在线程池中被取出，那么ThreadWorker空闲时间将永远不会到期，直到ThreadWorker被返回线程池后才重新开始空闲时间的计算
状态图：
关键代码：
1 private void ThreadWorking()
2 {
3 while (_status != ThreadWorkerStatus.Abort)
4 {
5 //WaitOne 返回false表示等待超时，true接到取消等待的通知
6 //这里利用AutoResetEvent.WaitOne的特性来设计闲时控制，false表示空闲到期，true表示新的任务开始
7 if (!_waitEvent.WaitOne(_idleTime))
8 {
9 if (!_isCanIdleExpired) //_isCanIdleExpired变量控制是否允许超时，例如被取出后将不能超时
10 continue;
11
12 _status = ThreadWorkerStatus.Abort;
13 _waitEvent.Close();
14 _waitEvent.Dispose();
15 if (OnIdleExpired != null)
16 OnIdleExpired(this, null); //空闲到期事件通知
17 return;
18 }
19 else if (_status == ThreadWorkerStatus.Abort)
20 return;
21
22 try
23 {
24 Working();
25 }
26 catch (Exception ex)
27 {
28 _logger.TraceEvent(TraceEventType.Error, (int)TraceEventType.Error, ex.ToString());
29 }
30 finally
31 {
32 _status = ThreadWorkerStatus.Idle;
33 if (OnWorkCompleted != null)
34 OnWorkCompleted(this, null); //任务完成事件通知
35 }
36 }
37 }
1 public void Work()
2 {
3 if (_status == ThreadWorkerStatus.Abort)
4 throw new InvalidOperationException("this ThreadWorker was Abort!");
5
6 if (_status == ThreadWorkerStatus.Working)
7 throw new InvalidOperationException("this ThreadWorker was working, unable to duplicate work!");
8
9 _status = ThreadWorkerStatus.Working;
10 _waitEvent.Set(); //通知线程有个新的工作要开始
11 }
ThreadWorkerPoolItem
要点设计：
- 链接ThreadWorker和线程池，线程池通过ThreadWorkerPoolItem控制ThreadWorker在线程池的取出，放回，销毁
- 通过订阅ThreadWorker的空闲到期事件OnIdleExpired，来完成线程池对线程的移除
- 通过订阅ThreadWorker的任务完成事件OnWorkCompleted，来完成线程返回线程池的操作
- 提供剩余空闲时间查询，来为线程池提供更优线程取出方案
完整代码：
1 public sealed class ThreadWorkerPoolItem
2 {
3 private ThreadWorkerPoolItemStatus _status;
4 private readonly ThreadWorkerBase _threadWorker;
5 private readonly ThreadWorkerPoolBase _threadWorkerPool;
6 private readonly int _idleTime;
7 private DateTime _startIdleTime;
8
9 internal ThreadWorkerPoolItem(ThreadWorkerPoolBase pool, ThreadWorkerBase threadWorker, ThreadWorkerPoolSettings poolSettings)
10 {
11 _threadWorkerPool = pool;
12 _threadWorker = threadWorker;
13 _threadWorker.OnIdleExpired += _threadWorker_OnIdleExpired;
14 _threadWorker.OnWorkCompleted += _threadWorker_OnWorkCompleted;
15 _threadWorker.Start();
16 _status = ThreadWorkerPoolItemStatus.Idle;
17 _idleTime = poolSettings.IdleTime;
18 }
19
20 void _threadWorker_OnWorkCompleted(object sender, EventArgs args)
21 {
22 _threadWorkerPool.Return(this);
23 }
24
25 void _threadWorker_OnIdleExpired(object sender, EventArgs args)
26 {
27 _threadWorkerPool.Remove(this);
28 }
29
30 internal ThreadWorkerPoolItemStatus Status
31 {
32 get
33 {
34 if (_threadWorker.Status == ThreadWorkerStatus.Abort || _status == ThreadWorkerPoolItemStatus.Abort)
35 return ThreadWorkerPoolItemStatus.Abort;
36
37 return _status;
38 }
39 }
40
41 internal int SurplusIdleTime
42 {
43 get
44 {
45 if (_status == ThreadWorkerPoolItemStatus.Take || _idleTime == -1)
46 return -1;
47
48 int idledTime = (int)(_startIdleTime - DateTime.Now).TotalMilliseconds;
49 if (idledTime >= _idleTime)
50 return 0;
51
52 return idledTime;
53 }
54 }
55
56 internal void SetTake()
57 {
58 _threadWorker.IsCanIdleExpried = false;
59 _status = ThreadWorkerPoolItemStatus.Take;
60 }
61
62 internal void SetIdle()
63 {
64 _startIdleTime = DateTime.Now;
65 _status = ThreadWorkerPoolItemStatus.Idle;
66 _threadWorker.IsCanIdleExpried = true;
67 }
68
69 internal ThreadWorkerBase ThreadWorker
70 {
71 get { return _threadWorker; }
72 }
73 }
ThreadWorkerPool
要点设计：
- 使用Lock配合ThreadWorkerPoolItem的状态来确保多线程下，每次取出的都是空闲的ThreadWorker
- 取出的超时设计，由于线程池有容量控制，高并发下必然导致线程池满负荷，提供超时设置，有利于使用者自行控制满负荷情况下的处理;ThreadWorkerPool将使用while+sleeping的方式，同时使用AutoResetEvent代替Thread.Sleep(timeout)来达到更佳的控制，当一个线程被放回线程池时，另一等待获取者立即获取，而无需等待下一次轮询的到来
关键代码：
1 protected bool TryTake(int timeout, out ThreadWorkerBase threadWorker)
2 {
3 threadWorker = null;
4 lock (_takeLocker)
5 {
6 ThreadWorkerPoolItem worker = null;
7 DateTime startWaitTime;
8 while (!_isDestoryed)
9 {
10 worker = _threadWorkerList.Where(e => e.Status == Core.ThreadWorkerPoolItemStatus.Idle).OrderByDescending(e => e.SurplusIdleTime).FirstOrDefault();
11 if (worker == null)
12 {
13 if (_threadWorkerList.Count < _settings.MaxThreadWorkerCount)
14 {
15 worker = this.CreatePoolItem(_threadWorkerList.Count + 1, _settings.IdleTime);
16 worker.SetTake();
17 _threadWorkerList.Add(worker);
18 threadWorker = worker.ThreadWorker;
19 return true;
20 }
21
22 startWaitTime = DateTime.Now;
23 if (!_takeWaitEvent.WaitOne(timeout))
24 {
25 threadWorker = null;
26 return false;
27 }
28
29 if (timeout != -1)
30 {
31 timeout = timeout - (int)(DateTime.Now - startWaitTime).TotalMilliseconds;
32 if (timeout <= 0)
33 {
34 threadWorker = null;
35 return false;
36 }
37 }
38 continue;
39 }
40
41 threadWorker = worker.ThreadWorker;
42 worker.SetTake();
43 return true;
44 }
45
46 threadWorker = null;
47 return false;
48 }
49 }
1 internal void Return(ThreadWorkerPoolItem item)
2 {
3 item.SetIdle();
4 _takeWaitEvent.Set();
5 }
ThreadWorkerPoolManager使用单例模式管理，代码过于简单这里就不贴了......
有兴趣的同学可以点击这里进行下载源码查看：Nutshell.ThreadWorkerPool.zip
github 开源地址: https://github.com/zcylife/Nutshell
