I'm currently in a situation where I need to deploy multiple Service Stack API's to the same server and getting an 'AppHostBase. Instance has already been set'. I've found this link: ServiceStack AppHost Is a Singleton? but it seems to be related to multiple versions of related APIs or versioned APIs. This is not my scenario. How can I (or is there a way to) configure multiple Service Stack API's which are completely unrelated and do not have any knowledge of each other to run simultaneously on the same server?
You should be able to setup two different applications in IIS as long as they run under different application pools. This will adhere to the guidance in the above linked answer of one single App Host for each App Domain.
It is not different from managing different applications (non ServiceStack) applications in IIS.
来源：https://stackoverflow.com/questions/17888996/two-service-stack-apis-on-the-same-iis-server