"Seamless" installation of a web service in C # in production - how?

Question

.NET

Introductory - there is a WCF service built into a Windows service. The service gives data for the web application and for the mobile application. For some reason, it takes 3-5 minutes from the start of the service to its full readiness for work. Accordingly, at this time, the web application and mobile applications are down and do not give data to users.
The question is - are there any ways to painlessly update the service so that there is no downtime during the restart?

Answer 1

In a nutshell, then introduce an additional layer of abstraction - the bus. The client makes a request to the bus, which in turn polls the available WCF service instances. While the WCF1 instance is being upgraded, the bus forwards the request to the standby WCF2. After deploying the update to WCF1, we switch to the updated service.