I'm currently working on an implementation of a stateful network server, let's say, FTP. As part of the currently thought architecture, there are multiple microservices that handling different user requests, and are going to be redundant through container environment. Now as the assumption above, the network protocol isn't customizable (should be compatible with every client that follow its RFC) and its "statefulness" is made through socket-to-client resolution.
My question is about the architecture - I'm trying to move away as much as possible the "statefulness" of the protocol from the microservices. I came up with the idea of having one stateful service, let's call it "session service" that makes the socket-to-client resolution and create the needed context for the request to be handled next by other, stateless, service. However, a further question raises - how can I add redundancy to that so called "session service"?
I failed to find any good example at the subject so I came here to hear your suggestions. How does it sounds? Do you observe a big overhead to the "session service" to be handle the statelessness of the following services? Have you ever encountered this kind of problem?