Nutshell.ThreadWorkerPool .Net线程池设计

功能描述：

1. 支持创建多个线程池，并统一管理
2. 支持不同线程池的容量控制，以及最少活动线程的设置
3. 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：

1. 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
2. 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：

　　

         private void ThreadWorking()
         {
             while (_status != ThreadWorkerStatus.Abort)
             {
                 //WaitOne 返回false表示等待超时，true接到取消等待的通知
                 //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
                 if (!_waitEvent.WaitOne(_idleTime))
                 {
                     if (!_isCanIdleExpired) //_isCanIdleExpired变量控制是否允许超时，例如被取出后将不能超时
                         continue;

                     _status = ThreadWorkerStatus.Abort;
                     _waitEvent.Close();
                     _waitEvent.Dispose();
                     if (OnIdleExpired != null)
                         OnIdleExpired(this, null); //空闲到期事件通知
                     return;
                 }
                 else if (_status == ThreadWorkerStatus.Abort)
                     return;

                 try
                 {
                     Working();
                 }
                 catch (Exception ex)
                 {
                     _logger.TraceEvent(TraceEventType.Error, (int)TraceEventType.Error, ex.ToString());
                 }
                 finally
                 {
                     _status = ThreadWorkerStatus.Idle;
                     if (OnWorkCompleted != null)
                         OnWorkCompleted(this, null); //任务完成事件通知
                 }
             }
         }

 　　　　 public void Work()
         {
             if (_status == ThreadWorkerStatus.Abort)
                 throw new InvalidOperationException("this ThreadWorker was Abort!");

             if (_status == ThreadWorkerStatus.Working)
                 throw new InvalidOperationException("this ThreadWorker was working, unable to duplicate work!");

             _status = ThreadWorkerStatus.Working;
             _waitEvent.Set(); //通知线程有个新的工作要开始
         }

　　ThreadWorkerPoolItem

　　要点设计：

1. 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
2. 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
3. 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
4. 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：

     public sealed class ThreadWorkerPoolItem
     {
         private ThreadWorkerPoolItemStatus _status;
         private readonly ThreadWorkerBase _threadWorker;
         private readonly ThreadWorkerPoolBase _threadWorkerPool;
         private readonly int _idleTime;
         private DateTime _startIdleTime;

         internal ThreadWorkerPoolItem(ThreadWorkerPoolBase pool, ThreadWorkerBase threadWorker, ThreadWorkerPoolSettings poolSettings)
         {
             _threadWorkerPool = pool;
             _threadWorker = threadWorker;
             _threadWorker.OnIdleExpired += _threadWorker_OnIdleExpired;
             _threadWorker.OnWorkCompleted += _threadWorker_OnWorkCompleted;
             _threadWorker.Start();
             _status = ThreadWorkerPoolItemStatus.Idle;
             _idleTime = poolSettings.IdleTime;
         }

         void _threadWorker_OnWorkCompleted(object sender, EventArgs args)
         {
             _threadWorkerPool.Return(this);
         }

         void _threadWorker_OnIdleExpired(object sender, EventArgs args)
         {
             _threadWorkerPool.Remove(this);
         }

         internal ThreadWorkerPoolItemStatus Status
         {
             get
             {
                 if (_threadWorker.Status == ThreadWorkerStatus.Abort || _status == ThreadWorkerPoolItemStatus.Abort)
                     return ThreadWorkerPoolItemStatus.Abort;

                 return _status;
             }
         }

         internal int SurplusIdleTime
         {
             get
             {
                 if (_status == ThreadWorkerPoolItemStatus.Take || _idleTime == -)
                     return -;

                 int idledTime = (int)(_startIdleTime - DateTime.Now).TotalMilliseconds;
                 if (idledTime >= _idleTime)
                     return ;

                 return idledTime;
             }
         }

         internal void SetTake()
         {
             _threadWorker.IsCanIdleExpried = false;
             _status = ThreadWorkerPoolItemStatus.Take;
         }

         internal void SetIdle()
         {
             _startIdleTime = DateTime.Now;
             _status = ThreadWorkerPoolItemStatus.Idle;
             _threadWorker.IsCanIdleExpried = true;
         }

         internal ThreadWorkerBase ThreadWorker
         {
             get { return _threadWorker; }
         }
     }

　　ThreadWorkerPool

　　要点设计：

1. 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
2. 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：

         protected bool TryTake(int timeout, out ThreadWorkerBase threadWorker)
         {
             threadWorker = null;
             lock (_takeLocker)
             {
                 ThreadWorkerPoolItem worker = null;
                 DateTime startWaitTime;
                 while (!_isDestoryed)
                 {
                     worker = _threadWorkerList.Where(e => e.Status == Core.ThreadWorkerPoolItemStatus.Idle).OrderByDescending(e => e.SurplusIdleTime).FirstOrDefault();
                     if (worker == null)
                     {
                         if (_threadWorkerList.Count < _settings.MaxThreadWorkerCount)
                         {
                             worker = this.CreatePoolItem(_threadWorkerList.Count + , _settings.IdleTime);
                             worker.SetTake();
                             _threadWorkerList.Add(worker);
                             threadWorker = worker.ThreadWorker;
                             return true;
                         }

                         startWaitTime = DateTime.Now;
                         if (!_takeWaitEvent.WaitOne(timeout))
                         {
                             threadWorker = null;
                             return false;
                         }

                         if (timeout != -)
                         {
                             timeout = timeout - (int)(DateTime.Now - startWaitTime).TotalMilliseconds;
                             if (timeout <= )
                             {
                                 threadWorker = null;
                                 return false;
                             }
                         }
                         continue;
                     }

                     threadWorker = worker.ThreadWorker;
                     worker.SetTake();
                     return true;
                 }

                 threadWorker = null;
                 return false;
             }
         }

         internal void Return(ThreadWorkerPoolItem item)
         {
             item.SetIdle();
             _takeWaitEvent.Set();
         }

　　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