一直对多线程不感冒,常见的场景下用不到这种技术,所以一直不愿去了解,但是遇到一些耗时的任务时就要考虑了。下面的例子是项目中遇到的,不想说这个如何的高深,只想说我也不是很了解到底如何工作的,到底带来了多少的效率提升。书上的理论要多枯燥有多枯燥,枯燥的我都不想去动手写里面的例子,下面的例子是实际用到的,还有些意思,不管怎么说开个头吧。
1.ManualResetEvent[] doEvents = new ManualResetEvent[threadCount];
通知一个或多个正在等待的线程已发生事件。 谁通知谁,发生的事情是指?一头雾水
2.ThreadPool.QueueUserWorkItem(new WaitCallback(DealData), new object[] { i, doEvents[i] });
线程池中创建一个线程池线程来执行指定方法(用委托WaitCallBack表示),并将该线程排入线程池的队列等待执行。
3.doEvent.Set();
将事件状态设置为终止状态,允许一个或多个等待线程继续。
4.WaitHandle.WaitAll(doEvents);
等待指定数组中的所有元素都收到信号。
来看下面的例子,
SendDealSucessEmailFromQueue()方法:threadCount是一个配置项,指定一次要开多少个线程,曾有人建议为了安全起见,机器是有好个核就开多少个线程这里假设是5,不知道有没有道理有待研究。dataNum也是一个配置项,指定一个线程要处理多少订单数据,这里假设是50。ManualResetEvent[] doEvents = new ManualResetEvent[threadCount],指定每次启动5个线程。然后循环doEvents[i] = new ManualResetEvent(false);使用false作为参数通知当前线程等待此线程完成之后再完成当前线程的工作。ThreadPool.QueueUserWorkItem(new WaitCallback(DealData), new object[] { i, doEvents[i] }); 在线程池中添加线程来执行DealData方法,给这个方法传递一个参数,这个参数是一个对象数组,数组的第一项是当前第几个线程,就是线程号,第二个是线程的事件(请原谅我这么翻译,貌似没有看到ManualResetEvent这个类的中文名字是什么,看样子像手动重置事件,我这里简称线程事件)。注意for循环外面的一句话WaitHandle.WaitAll(doEvents);,这里先不解释待说完循环中调用的DealData方法之后再说。
DealData(object eventParams)方法:上面说到给他传递的参数是一个对象数组,所以int threadId = (int)(((object[])eventParams)[0]); ManualResetEvent doEvent = (ManualResetEvent)(((object[])eventParams)[1]);这两句很好理解,就是从这个对象数组中把实参值转换过来。int tmpCount = orderList.Count / threadCount;计算每个线程要处理的订单数量,要说的是因为要判断存在有要处理的订单才会开线程来处理,所以使用静态变量orderList。下面的这个for循环需要耐心琢磨,其实在SendDealSucessEmailFromQueue()这个方法执行完之后就已经开了5个线程,这时每个线程在做些什么事情我们是不能控制的,只知道有5个线程像脱缰野马一样地跑,在执行DealData(object eventParams)的时候是不知道当前是的线程是这5匹马中的那一匹,所以在这个for循环中我们就需要给他们分配工作,具体来说就是第0个线程处理0-49个订单,第1个线程处理50-99个,第2个线程处理100-149个,第3个线程处理200-249个,注意我这里都是用数组下标来解释。分配完即执行,执行完之后调用doEvent.Set();将当前线程置为终止。
再回到SendDealSucessEmailFromQueue()方法的最后一句WaitHandle.WaitAll(doEvents);等待线程事件中的所有任务执行完成之后继续当前线程,就是继续往下跑了,就是主程序了,可以理解为回到Main()方法中了。
/// <summary>/// 处理订单邮件/// </summary>public class OrderEmailProcess{/// <summary>/// 日志/// </summary>private static readonly ILog logger = LogManager.GetLogger(typeof(OrderEmailProcess));static List<Corp.CorpFlightADTKJob.Entity.FltOrderInfoEntity.OrderInfoEntity> orderList = new List<Entity.FltOrderInfoEntity.OrderInfoEntity>();static int threadCount = 0;static int dataNum = 0;/// <summary>/// 发送成交确认邮件/// 因为发邮件接口中占用了emailtype:8,所以使用4096,这里需要处理emailtype/// </summary>public static void SendDealSucessEmailFromQueue(){threadCount = int.Parse(ConfigurationManager.AppSettings["ThreadCount"]);dataNum = int.Parse(ConfigurationManager.AppSettings["DataNum"]);string logMsg = "";orderList = CorpProcessDB.GetDealConfirmEmailQueue(ConnStrFactory.CorpProcessDB_Select, threadCount * dataNum);if (orderList != null && orderList.Count > 0){//记录日志for (int i = 0; i < orderList.Count; i++){logMsg += string.Format("OrderID:{0} Uid:{1} EmailType:{2}", orderList[i].OrderID, orderList[i].Uid, orderList[i].EmailType) + "\n";}logger.Info("自动发邮件", logMsg);ManualResetEvent[] doEvents = new ManualResetEvent[threadCount];for (int i = 0; i < threadCount; i++){doEvents[i] = new ManualResetEvent(false);ThreadPool.QueueUserWorkItem(new WaitCallback(DealData), new object[] { i, doEvents[i] });}WaitHandle.WaitAll(doEvents);}}/// <summary>/// 处理线程方法/// </summary>/// <param name="eventParams"></param>private static void DealData(object eventParams){int threadId = (int)(((object[])eventParams)[0]); //当前线程IDManualResetEvent doEvent = (ManualResetEvent)(((object[])eventParams)[1]);int tmpCount = orderList.Count / threadCount; //平均每个线程处理数据for (int i = 0; i < orderList.Count; i++){if (i < (threadId) * tmpCount)continue;if ((i >= (threadId + 1) * tmpCount) && threadId != (threadCount - 1))break;doDetailEvent(orderList[i]);}doEvent.Set();}/// <summary>/// 发邮件/// </summary>/// <param name="item"></param>/// <param name="threadId"></param>private static void doDetailEvent(Corp.CorpFlightADTKJob.Entity.FltOrderInfoEntity.OrderInfoEntity order){int emailsendtime = order.EmailType;if ((emailsendtime & 8) == 8){emailsendtime = emailsendtime + 4088;}CorpEmaiWSlHelper.SendCorpConfirmMail(order.OrderID, order.Uid, "N", emailsendtime, ""); }}
如果你觉得上面的例子跑不起来,那么下面的例子可以让你在自己的机器上跑起来。这是一个web页面,OrderInfoEntity这个类写在另外一个文件中,这里和在一起展示。
public partial class About : System.Web.UI.Page{int threadCount = 5;int dataNum = 50;static string msg = "";protected void Page_Load(object sender, EventArgs e){msg = "";SendDealSucessEmailFromQueue();Response.Write(msg);}public List<OrderInfoEntity> orderList;public void SendDealSucessEmailFromQueue(){threadCount = 5;dataNum = 50;orderList = GetDealConfirmEmailQueue(threadCount * dataNum);if (orderList != null && orderList.Count > 0){ManualResetEvent[] doEvents = new ManualResetEvent[threadCount];for (int i = 0; i < threadCount; i++){doEvents[i] = new ManualResetEvent(false);ThreadPool.QueueUserWorkItem(new WaitCallback(DealData), new object[] { i, doEvents[i] });}WaitHandle.WaitAll(doEvents);}}public void DealData(object eventParams){int threadId = (int)(((object[])eventParams)[0]); //当前线程IDManualResetEvent doEvent = (ManualResetEvent)(((object[])eventParams)[1]);int tmpCount = orderList.Count / threadCount; //平均每个线程处理数据for (int i = 0; i < orderList.Count; i++){if (i < (threadId) * tmpCount)continue;if ((i >= (threadId + 1) * tmpCount) && threadId != (threadCount - 1))break;doDetailEvent(orderList[i]);}doEvent.Set();}static void doDetailEvent(OrderInfoEntity order){msg += order.OrderID.ToString() + "</br>";}/// <summary>/// 添加订单列表/// </summary>/// <param name="p"></param>/// <returns></returns>private static List<OrderInfoEntity> GetDealConfirmEmailQueue(int p){List<OrderInfoEntity> result = new List<OrderInfoEntity>();for (int i = 0; i < p; i++){OrderInfoEntity entity = new OrderInfoEntity(i + 1);result.Add(entity);}return result;}}public class OrderInfoEntity{private int _orderID;public int OrderID{ get { return _orderID; } set { _orderID = value; } }public OrderInfoEntity(int orderid){this._orderID = orderid;}}
这个方法也是异步读取的方法,不过简单一些。
#region 异步读取数据long logID1 = RequestManager.newSubRequest(), logID2 = RequestManager.newSubRequest(), logID3 = RequestManager.newSubRequest();Task<List<CorpFlightSearchFlightsEntity>> taskNormalFlts = Task.Factory.StartNew<List<CorpFlightSearchFlightsEntity>>(() => SearchNormalFlights(searchRequest, logID1));Task<List<CorpFlightSearchFlightsEntity>> taskCorpFlts = Task.Factory.StartNew<List<CorpFlightSearchFlightsEntity>>(() => SearchCorpFlightsOnly(searchRequest, logID2));Task<List<CorpFlightSearchFlightsEntity>> taskMultiSpecialFlts = null;if (searchRequest.FlightWay == "D"){taskMultiSpecialFlts = Task.Factory.StartNew<List<CorpFlightSearchFlightsEntity>>(() => SearchMultiSpecialFlights(searchRequest, logID3));Task.WaitAll(taskNormalFlts, taskCorpFlts, taskMultiSpecialFlts);}else{Task.WaitAll(taskNormalFlts, taskCorpFlts);}normalFlts = taskNormalFlts.Result;corpFlts = taskCorpFlts.Result;multiSpecialFlts = taskMultiSpecialFlts != null ? taskMultiSpecialFlts.Result : null;#endregion
据新来的高手说下面这样写才能保证速度,上面的方法只能提高吞吐量,并不能防止阻塞。
Task<List<CorpFlightSearchFlightsEntity>> taskNormalFlts = Task.Factory.StartNew<List<CorpFlightSearchFlightsEntity>>(() => SearchNormalFlights(searchRequest, logID1));Task<List<CorpFlightSearchFlightsEntity>> taskCorpFlts = Task.Factory.StartNew<List<CorpFlightSearchFlightsEntity>>(() => SearchCorpFlightsOnly(searchRequest, logID2));Task<List<CorpFlightSearchFlightsEntity>> taskMultiSpecialFlts = null;if (searchRequest.FlightWay == "D"){taskMultiSpecialFlts = Task.Factory.StartNew<List<CorpFlightSearchFlightsEntity>>(() => SearchMultiSpecialFlights(searchRequest, logID3));//Task.WaitAll(taskNormalFlts, taskCorpFlts, taskMultiSpecialFlts);normalFlts = taskNormalFlts.ContinueWith(t => t.Result).Result;corpFlts = taskCorpFlts.ContinueWith(t => t.Result).Result;multiSpecialFlts = taskMultiSpecialFlts.ContinueWith(t => t.Result).Result;}else{//Task.WaitAll(taskNormalFlts, taskCorpFlts);normalFlts = taskNormalFlts.ContinueWith(t => t.Result).Result;corpFlts = taskCorpFlts.ContinueWith(t => t.Result).Result;}normalFlts = taskNormalFlts.Result;corpFlts = taskCorpFlts.Result;multiSpecialFlts = taskMultiSpecialFlts != null ? taskMultiSpecialFlts.Result : null;
还有一种简写方法,在没有前后依赖关系,没有返回值的情况下还可以使用Parallel.Invoke方法,如下:
if (this._appFlightsList.Count > 0){Parallel.Invoke(() =>{ Parallel.ForEach(_appFlightsList, ShowFlightsUICommon.SetAppFlight);this._appFlightsList.Sort(AppFlightSorter.CorpSort);},() =>{if (this._passengerTypeString.Trim().ToUpper() == "ADU"){if (this._lowestPrices != null && this._lowestPrices.Count > 0){this._lowestPrices.Sort(LowestPriceSoter.CompareLowestPriceByDate);} ShowFlightsUICommon.SetCorpSingleTripAppSpecialSummary4OnlineCNOnly(this._specialSummary, corpFlightsResponse.SingleTripSummaryList);if (this._corpSearchMultipleSpecialResponse != null &&this._corpSearchMultipleSpecialResponse.Groups.Count > 0){ShowFlightsUICommon.SetCorpMultipleAppSpecialSummary(this._specialSummary,this._corpSearchMultipleSpecialResponse.Groups);}if (this._corpSearchTransitSpecialResponse != null &&this._corpSearchTransitSpecialResponse.LowGroups.Count > 0){ShowFlightsUICommon.SetCorpTransitAppSpecialSummary(this._specialSummary,this._corpSearchTransitSpecialResponse.LowGroups);}ShowFlightsUICommon.SetCorpAppSpecialPrice(this._specialSummary,this._IsCalcNetPrice,this._SaleRate);FlightProcess.FlightsFilterWithAccount(this._specialSummary,this._AccountID);}});}