Periodic operations in a Self-Hosted WCF Service using Timers

I know that it is not a good idea to have timers inside a WCF开发者_开发百科 service class that is hosted inside IIS since these are meant to have short lifetimes. And from the advice here it also sounds like having a service is the best way to go for that situation.

But has anyone tried using timers inside a self-hosted service in production? We have a windows service that acts as a client and uses timers to do periodic operations at the moment.

This is fine for most cases, but I am concerned about the robustness of the design: some of the operations are critical (financial system calculation triggers). Since the WCF service and the windows service are two components, ensuring both are running is difficult.

If I moved the critical operations to a timer inside the WCF Service I remove that problem, but what else should I be concerned about then?

If I understand correctly, your question is actually about IIS-hosted WCF services, is that right?

IIS controls the application pool that your WCF service runs in. That means that IIS may decide to recycle your application pool and all the apps/services in it. Then your service only gets activated again once it is called by a client. So, scheduling in WCF services or ASP.NET applications cannot be relied on.

The picture of course changes if you can self-host your WCF service. Then there is no IIS application pooling to take into account, and you can schedule at will. Therefore, if you need the combination of WCF + scheduling, it's best to create a Windows service that will include both.