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Editorial Team
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Asked: 2026-05-25T02:15:01+00:00

I’d like to start using asynchronous processing in IIS. Edit: I’m talking about using

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I’d like to start using asynchronous processing in IIS. Edit: I’m talking about using the task parallel library.

For example, on certain page loads I want to log a bunch of crap, send an email, update some tables, etc. But I don’t want to make the user wait for me to log all that crap.

So normally what I do is I have a static Queue that I push the log info onto, and then I have a cron job that calls a special page every 10 minutes whose OnLoad flushes out the queue. This works, but it’s kind of clunky to setup, especially when you want to log 50 things. I’d rather do this: 

Task.CreateNew(() => Log(theStuff));

However I’m terrified of running tasks in IIS because one slip up and your entire website goes down.

So now I have

SafeTask.FireAndForget(() => Log(theStuff));

This wraps the delegate in some try/catch and passes it into Task.CreateNew. So if someone changes something that affects something else that generates an exception somewhere else that accidentally gets thrown on the task thread, we get a notification instead of a crashed website. Also, the error notification inside the catch is also inside its own try/catch, and the catch for that also has a try/catch that tries to log in a different way.

Now that I can safely run stuff asynchronously in IIS, what other things do I need to worry about before I can start using my SafeTask class?

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1 Answer

  1. Editorial Team

    Every request in IIS and .net is processed in one thread by default. This thread comes from a thread pool called the “Application Pool”. Existing threads are reused so you can’t really use them for thread state unless you clear or set it every time. You define the size of this thread pool using a formula from MSDN in the machine.config or even your web.config.

    Now, every async function call is put on a different thread. This includes async web service calls, async page functions, async delegates, etc. This thread comes from the “application pool” thus reducing the number of thread available for IIS to service new requests.

    Most likely, your application will work just fine while using async function calls. In case you are worried or you have a lot of async tasks then you may want to create your own thread pool or look at SmartThreadPool on codeplex.

    Hope this helps.

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