web的定时任务

　　web开发中，总是会需要一些定时任务，比如发email(在前台等email的发送随时准备接受User的雷霆一怒吧)，比如每月初发报表给老板们。

　　Global.asax.cs 的Application_Start 中设置一个System.Timers.Timer，定时执行一个方法就做到了。

　　但是比较郁闷的问题是，IIS一段时间没有人访问时会回收，System.Timers.Timer也就被回收掉了。

　　网上搜索，人家的建议是Application_End中重新开一个网页，但是经过试验，发现2个需要注意的地方:

     1)一定要睡觉       Thread.Sleep(1000*10);  一定不能少,猜想的原因在注释中。

     2)回收问题    之前没睡觉，1个小时IIS就回收了。后来我想在Timer里面增加访问网站(可以在注释中看到) ，但是没注意"计划生育"，就不断地增加访问网站的数量，后来也是1个小时左右挂了。加了一个计数功能，发现数量比较大的时候会塞死，后面增加了回收部分。解决了部分问题，再加上"计划生育"，Lock和设定Application["Timer"]等。

 　　　　　　　　 receiveStream.Close();
                myHttpWebResponse.Close();
                myHttpWebResponse.Close();
 3）最后发现，比较保险的方法是在定时任务中增加一个访问网页的动作，这样Session就一直会保持2个，双保险了。

using System;
using System.IO;
using System.Threading;
using System.Timers;
using System.Web;
using System.Web.Caching;


namespace WebService
{
    public class Global : System.Web.HttpApplication
    {
        object objLock = new object();
        protected void Application_Start(object sender, EventArgs e)
        {

            StreamWriter sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
            sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application_Start");
            sw.Close();

            //定义定时器
            //1000表示1秒的意思
            lock (objLock)
            {
                if (Application["Timer"] == null)
                {
                    System.Timers.Timer myTimer = new System.Timers.Timer(1000 * 60);
                    //TaskAction.SetContent 表示要调用的方法
                    myTimer.Elapsed += new System.Timers.ElapsedEventHandler(TaskAction.SetContent);
                    myTimer.AutoReset = true;
                    myTimer.Enabled = true;
                    Application["Timer"] = myTimer;

                    StreamWriter sw1 = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                    sw1.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application_Start Start Timer");
                    sw1.Close();
                }
            }
            Application["Count1"] = 0;

        }
        

        protected void Session_Start(object sender, EventArgs e)
        {
            Application["Count1"] = (int)Application["Count1"] + 1;
            Session["Time"] = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
            StreamWriter sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
            sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Session_Start:" + Session["Time"].ToString() + ":" + Application["Count1"].ToString());
            sw.Close();

            lock (objLock)
            {
                if (Application["Timer"] == null)
                {
                    System.Timers.Timer myTimer = new System.Timers.Timer(1000 * 60);
                    //TaskAction.SetContent 表示要调用的方法
                    myTimer.Elapsed += new System.Timers.ElapsedEventHandler(TaskAction.SetContent);
                    myTimer.AutoReset = true;
                    myTimer.Enabled = true;
                    Application["Timer"] = myTimer;

                    sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                    sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Session_Start Start Timer");
                    sw.Close();
                }

            }

        }


        protected void Application_BeginRequest(object sender, EventArgs e)
        {

        }

        protected void Application_AuthenticateRequest(object sender, EventArgs e)
        {

        }

        protected void Application_Error(object sender, EventArgs e)
        {

        }

        protected void Session_End(object sender, EventArgs e)
        {
            Application["Count1"] = (int)Application["Count1"] - 1;
            if (Session.Contents["Time"] == null)
            {
                Session.Contents["Time"] = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
            }
            StreamWriter sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
            sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Session_End:" + Session.Contents["Time"].ToString() + ":" + Application["Count1"].ToString());
            sw.Close();

            lock (objLock)
            {
                if (Application["Timer"] == null)
                {
                    System.Timers.Timer myTimer = new System.Timers.Timer(1000 * 60);
                    //TaskAction.SetContent 表示要调用的方法
                    myTimer.Elapsed += new System.Timers.ElapsedEventHandler(TaskAction.SetContent);
                    myTimer.AutoReset = true;
                    myTimer.Enabled = true;
                    Application["Timer"] = myTimer;

                    sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                    sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Session_End Start Timer");
                    sw.Close();
                }
            }

        }

        protected void Application_End(object sender, EventArgs e)
        {
            StreamWriter sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
            sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application_End:1:" + Application["Count1"].ToString());
            sw.Close();
            try
            {
                //下面的代碼是關鍵，可解決IIS應用程序池自動回收的問題 (原注釋)
                //猜想原因:空出時間讓IIS清理之後再添加東西進去,避免清理的時候正好碰到訪問網站
                //         或者就是想睡睡覺?
                Thread.Sleep(1000*10);

                string url = "http://10.40.1.186:456/webform1.aspx";
                System.Net.HttpWebRequest myHttpWebRequest = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(url);
                myHttpWebRequest.ServicePoint.Expect100Continue = false;
                System.Net.HttpWebResponse myHttpWebResponse = (System.Net.HttpWebResponse)myHttpWebRequest.GetResponse();
                System.IO.Stream receiveStream = myHttpWebResponse.GetResponseStream();//得到回写的字节流
                receiveStream.Close();
                myHttpWebResponse.Close();
                myHttpWebResponse.Close();
            }
            catch (Exception ex)
            {
                StreamWriter sw2 = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                sw2.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application_End Exception:" + ex.ToString());
                sw2.Close();
            }
            //sw.WriteLine(receiveStream.ToString());
            StreamWriter sw1 = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
            sw1.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Application_End:2:" + Application["Count1"].ToString());
            sw1.Close();

        }
    }
    public static class TaskAction
    {

        /// <summary>
        /// 定时器委托任务 调用的方法
        /// </summary>
        /// <param name="source"></param>
        /// <param name="e"></param>
        public static void SetContent(object source, ElapsedEventArgs e)
        {
            try
            {
                StreamWriter sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Timer Work");
                sw.Close();

                
                string url = "http://10.40.1.186:456/webform1.aspx";
                System.Net.HttpWebRequest myHttpWebRequest = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(url);
                myHttpWebRequest.ServicePoint.Expect100Continue = false;
                System.Net.HttpWebResponse myHttpWebResponse = (System.Net.HttpWebResponse)myHttpWebRequest.GetResponse();
                System.IO.Stream receiveStream = myHttpWebResponse.GetResponseStream();//得到回写的字节流
                receiveStream.Close();
                myHttpWebResponse.Close();
                myHttpWebResponse.Close();

                //sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                //sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":SetContent END:2");
                //sw.Close();
            }
            catch (Exception ex)
            {
                StreamWriter sw = new StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "log.txt", true);
                sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + ":Timer Work Exception:" + ex.ToString());
                sw.Close();
            }

        }

    }
}