Update Client Status on Long Running Job

Every once in a while I come across a question like: "I have a web application that has a long running job. It could take up to a few dozen minutes to complete. How can I keep the client status updated and not causing a timeout?"

The problem with a web application like this is that if the job run too long, it will cause a script timeout error. One can opt to increase the script timeout to prevent this but when you actually have an error, it would take forever before the client is notified of the error.

People often think that AJAX is the only solution to this problem but it isn't. But with a little clever coding, combining javascript with server side code, you can accomplish this. You can apply this technique to classic ASP or ASP.NET or whatever techonolgy or language you choose to use.

What we need to do is find a way to continuously sending data to the browser so that it doesn't time out on us. with vbscript and vb.net Repsonse.Buffer & Response.Flush can take care of this quite nicely.

So now we have the data streaming to the client, how to we update the status? The answer is javascript. We can script a function and take advantage of the ability to dynamically changing the content of the div or span tag to update the status when we receive some data from the server.

Please examine the source code for the complete example.