ASP.NET, asynchronous call to another page, return response immediately

Question

Hi all!

The problem is as follows: An external server sends incoming SMS messages converted to HTTP requests into my sometimes very time-consuming .aspx page. If no response is returned to the external server in 20 seconds, this is considered as an timeout and the same message is sent to my aspx page again (and maybe again....)

The optimal solution for me would be that the aspx page reads the incoming message (as an HTTP request to the aspx page), starts the processing of the message in another thread, and immediately renders response back to the external server. The external server has no interest in other stuff than the HTTP status (normally 200). When the processing of the message is completed this results in an entry into the log file of the application.

The processing of the message is done by making another web request to an aspx page, and I have tried to use the BeginGetResponse method for the web request, and have created a handler for handling of the completed web request to the processing page. The problem is that the handler seems to not be called, most likely because the aspx page's lifecycle is ended before the asynchrounous web request is completed.

Has anyone any good solution for this problem? I have also looked at the async page model, but this also seems to not be a solution for me because the response should be returned to the external server before the processing of the message is completed.

Regards, Eivind

Answer 1

I'd be very wary of using threads in ASP.Net in this manner. Using them to take advantage of multiple cores is one thing. Using them to set up some kind of concurrent response technique seems like a recipe for disaster. Especially when there is a far more elegant solution.

Your ASP.Net application should merely take the message and toss it in a database and send the success reply. It's job is done. The job of delivering the message should be handled by some kind of service or daemon. Windows Services are kind of a pain to build and maintain so perhaps just a scheduled task that runs every 30 seconds or so checking for queued messages in the DB would suit your purposes just fine.

I've seen a lot of people try to use threads in ASP.Net when they really should just be creating a background service. The results are never as reliable as you would hope.

Answer 2

Async page model is definitely not the solution. Have you tried using the unload event to do EndRequest? I really don't know if that would work but it is worth a try. The most robust way is to use Windows Service to run the async request.