WCF ConcurrencyMode Single and InstanceContextMode PerCall

Question

I have an issue with my wcf service config. I would like every call to my service create a new instance of the service. For the concurrency I would like to one call is fini

Answer 1

What you have there will result in a new instance of the service spinning up with each request (that's what PerCall does).

This should do it:

[ServiceBehavior(ConcurrencyMode=ConcurrencyMode.Single, InstanceContextMode=InstanceContextMode.Single)]

FYI if you do this you'll lose all scalability. You'll have a single instance of a single threaded service to respond to all requests.

Answer 2

I know this question was marked as answered, but there is a better alternative:

If you use a InstanceContextMode.Single then you will reuse the same instance for all calls. If your service is long running this requires your code to manage resources perfectly, since it will never be garbage collected without a service restart.

Instead keep the InstanceContextMode.PerCall for “every call to my service creates a new instance” and then use throttling: Set the max concurrent instances to 1. The MSDN documentation does exactly this as one of the examples.