What is the correct use of the ASP.NET Thread Pool?

Question

Hi there,

My scenario is this, I have a file that slowly gets populated over the course of an hour or two (mp3, video, etc). As this file is populated many users are connected to the server to receive new data as it is added to the server.

At the moment each visitor connects to the server, and an IHttpAsyncHandler allocates a thread from the thread pool to handle the request. However using the default thread pool settings, this means that only 20 visitors can connect to a server (single processor) at a time.

Because most of the time these threads are simply waiting for new data, what would be the best way to release the thread to the pool, and have it re-activate when new data is available.

Many Thanks, Ady

Answer 1

I would just use regular Threads for this purpose. The .NET ThreadPool is not really designed to support the releasing and re-activation of (long-running) threads depending on their internal state... at the very least, you would have to do some creative programming to achieve the desired behavior if you stick with a ThreadPool (i.e. break the logic into small asynchronous tasks that get executed by the ThradPool).

If you go with Thread, then you will have direct control to all the active threads so you can accept more visitors at the same time.

Answer 2

F# has a feature called Asynchronous Workflows that is ideally suited to this sort of thing. When your code is waiting on an external data source, the thread is returned to the thread pool for other uses. When new data arrives, the workflow gets a thread out of the pool and uses it to resume your code where you left off. In this way you never have to tie up a thread that's doing nothing but waiting on I/O.

It may be overkill to learn a new language just for this one use, but F# towers over every other CLR language when it comes to async I/O, and it's a really fun language, besides.