What is the lifecycle of an IIS-hosted (http) WCF service?

Question

I have a dependency injection container setup in my application and I'm thinking that composing the container every time a WCF service request comes in is going to be inefficient.

Can somebody explain to me, for an http/IIS hosted WCF service, what the lifecycle of the service is? If I can figure this out, I can make an educated decision on where the container is to be stored, instantiated, destroyed, etc.

Answer 1

If your InstanceContextMode is PerCall, the service class will be created from scratch for every incoming request, and then disposed of when it's done.

If your InstanceContextMode is PerSession, the service class will be created and used to service one given client for the duration of the session (or until an "InactivityTimeout" is encountered, or an error occurs).

If your InstanceContextMode is Single (singleton), the service class will be created when the first request comes in and will stay in memory as long as requests keep coming in, as long as no error occurs and no inactivityTimeout is reached.

So, there you have it! Of course, the concurrency mode (for PerSession and Single services) will also come into play to make things just a tad more "interesting"

Answer 2

As you mention that you were trying to integrate WCF service instantiation with a dependency injection container, I'd just like to say that I've had a very positive experience using the Castle WCF Integration Facility to do just that.

It's specific to the Castle Windsor dependency injection container but with it being open source you can look inside and understand some of the challenges and solutions provided.