Does an HttpHandler listen for a disconnect from the browser?
My guess is "no" since it seems to be mostly/only used for dynamic file creation, so why would it?
But I can't find an answer in the docs or goog.
Many thanks in advance!
Background
I'd like to "abort" an HttpHandler because currently, I allow huge excel exports (~150k sql rows, so ~600k html lines). For reasons almost as ridiculous as the code, I have a query that fires for as many sql rows that the user tries to export. As you can imagine, this takes a very long time.
I think I'm getting backed up with worker processes because users probably get frustrated with the lag, and try again with a smaller result. I currently flush the worker procs automatically every 30 min, but I'd rather cleanup more quickly.
I don't have the time to clean up the sql right now, so I'd like to just listen for an "abort" from the client and kill the handler if "aborted".
What you're hoping to accomplish by listening for a client connection drop won't really help solve your problem at all. The core of your problem is a long running task being kicked off in an HttpHandler directly.
In this case, even if you could listen for a client disconnect it wouldn't ever be acted upon as your code will be too busy executing to listen for it.
The only way to properly determine progress and perform actions during long running processes such as this is to ensure that your code is multi-threaded. The problem with doing this in ASP.NET for long running processes is they'll suck up threads from the thread pool needed to serve your pages. This could result in your website hanging or responding very slowly, as you've been experiencing.
I would recommend writing a Windows Service to handle these long running jobs and having it spit the results into a staging directory. I would then use MSMQ or similar to throw the request to the service for processing.
Ultimately, you want to get this long running thread outside of ASP.NET where you can take advantage of the benefits that multi-threading can offer you. Such as, the ability to report back the progress and to abort when needed.