I have a WCF service (written in .NET 4) running under IIS 7.5 on Windows 2008 R2 64-bit.
I created a test tool that spawns 10-20 (or more) threads - each thread creates a random payload and hits the server. On the server, I log all the accesses and I can see the thread IDs that are engaged in IIS.
Regardless of how many client requests hit the server (at the same time), the server only uses 2 threads. It basically cycles between them.
But then, out of the blue, IIS will start using as many threads as the number of requests that I throw at it. And then later it will drop down to using 1 or 2 threads.
Can someone explain this behavior and what I can do to fix it?