C # scheduled startup of Web Applications

Complex business applicationsProgramIn, sometimes one or more tasks are required to be scheduled at a certain time or within a certain interval, such as regular backup or Database Synchronization, and regular email sending, we call it a scheduled task. There are also many ways to schedule tasks. You can use SQLAgent to execute stored procedures, use Windows Task Scheduling programs, or use Windows Services to schedule tasks, these methods are good solutions. However, for Web applications, the implementation of these methods is not very simple, host service providers or cannot directly provide such services, or you need to pay a lot of extra fees. This article introduces a simple method that is directly used in Web applications. This method can be easily implemented without any additional configuration.

Because the ASP. Net Site runs as a web application and is not restricted by threads, we can easily create and destroy a scheduler task in application_start and application_end events.

The ASP. NET Framework application is created when a request is sent to the server for the first time.Code. When the first request is sent, an httpapplication instance pool is created and application_start event is triggered.
The httpapplication instance processes the request and subsequent requests until the last instance exits and triggers the application_end event.

How to solve the problem that IIS application pool recycle causes timed execution program stop in application_start

The principle is to send a Web request at the end of the application to access the website and start application_start.

Void  Application_end (  Object  Sender, eventargs E)
{
  //  Code that runs when the application is closed
  //  Solve application pool recycle Problems  
  System. Threading. thread. Sleep (  5000  );
  String  Strurl  =    "  Website address  "  ;
System. net. httpwebrequest _ httpwebrequest  =  (System. net. httpwebrequest) system. net. webrequest. Create (strurl );
System. net. httpwebresponse _ httpwebresponse  =  (System. net. httpwebresponse) _ httpwebrequest. getresponse ();
System. Io. Stream _ stream  =  _ Httpwebresponse. getresponsestream ();  //  Get the write-back byte stream  
 } 

The following describes how to plan tasks on a web site. In our example, information is regularly added to the file. As an example, the current time is regularly written to the file.

The unit of work of a scheduled task is called a job. The following code describes a common interface that can be executed by the scheduling engine for all tasks, each task implements the execute method for the scheduling engine to call:

Public interface ischedulerjob
{
Void execute ();
}

As mentioned above, our example is to write data to a file as a character date. The following describes how to implement this task:

 Public     Class  Samplejob: ischedulerjob
{
  Public     Void  Execute ()
{
  // The physical path of the file. cstest is the virtual directory name, and F: \ Inetpub \ wwwroot \ cstest is the physical path.  
  String  P  =     @"  F: \ Inetpub \ wwwroot \ cstest  "  ;
  //  Create the schedulerjob folder under the root directory of the virtual directory and set the permission to anonymous,
  //  Schedulerjob.txt is the file we wrote.  
 String  File_name  =  P  +     "  \ Schedulerjob \ schedulerjob.txt  "  ;
  //  Get the current server time and convert it to a string  
  String  C  =  System. datetime. Now. tostring ( "  Yyyy-mm-dd hh: mm: SS  "  );
  //  Indicates whether a new file is a scalar.  
  Bool  Flag  =     False  ;
  //  If the file does not exist, create a new one.  
  If (  !  File. exists (file_name ))
{
Flag  =     True  ;
Streamwriter SR  =  File. createtext (file_name );
Sr. Close ();
}
  //  Write content to a file  
  Streamwriter x  =     New Streamwriter (file_name,  True  , System. Text. encoding. Default );
  If  (FLAG) X. Write (  "  Scheduled task test starts:  "  );
X. Write (  "  \ R \ n  "  +  C );
X. Close ();
}
} 

Next, we will create a configuration object to tell the scheduling engine what task to execute and the interval between the execution.

 Public    Class  Schedulerconfiguration
{
  //  Interval  
  Private     Int  Sleepinterval;
  //  Task List  
  Private  Arraylist jobs  =    New  Arraylist ();

  Public     Int  Sleepinterval {  Get  {  Return  Sleepinterval ;}}
  Public  Arraylist jobs {  Get  {  Return  Jobs ;}}

 //  Constructor of the scheduling configuration class  
  Public  Schedulerconfiguration (  Int  Newsleepinterval)
{
Sleepinterval  =  Newsleepinterval;
}
} 

The following is the scheduling engine, which periodically executes the task of the configuration object.

 Public     Class  Scheduler
{
  Private Schedulerconfiguration Configuration  =     Null  ;

  Public  Scheduler (schedulerconfiguration config)
{
Configuration  =  Config;
}

  Public     Void  Start ()
{
  While  (  True )
{
  //  Execute each task  
  Foreach  (Ischedulerjob job  In  Configuration. Jobs)
{
Threadstart mythreaddelegate  =     New  Threadstart (job. Execute );
Thread mythread  =     New Thread (mythreaddelegate );
Mythread. Start ();
Thread. Sleep (configuration. sleepinterval );
}
}
}
} 

All preparations have been completed. The following describes how to activate the engine. In order to make our task plan run, we. asax. in the CS file applicatio_start and application_end, create and destroy a thread where the scheduling process runs. The running interval here is 3 seconds.

 Public  System. Threading. Thread schedulerthread  =     Null  ;
  Protected     Void  Application_start (Object sender, eventargs E)
{
Schedulerconfiguration config =     New  Schedulerconfiguration (  1000  *  3  );
Config. Jobs. Add (  New  Samplejob ());
Scheduler  =     New  Scheduler (config );
System. Threading. threadstart mythreadstart  =    New  System. Threading. threadstart (schedstart. Start );
System. Threading. Thread schedulerthread  =     New  System. Threading. Thread (mythreadstart );
Schedulerthread. Start ();
} 

Finally, destroy the program upon exit:

Protected VoidApplication_end (Object sender, eventargs E)
{
If(Null ! =Schedulerthread)
{
Schedulerthread. Abort ();
}
}
 

All right, create a C # web application project in vs. net, create taskscheduler. CS class, and modify the corresponding global. asax. CS file. In order to see the effect, we create another form webform1.aspx and refresh it regularly to check the data we recorded:

<% @ page Language = "C #" codebehind = "webform1.aspx. CS "autoeventwireup =" false "
inherits =" cstest. webform1 "%>



Web Application example of executing a scheduled task in a program