I have microservices that need to be stateful. I also want the microservices to be scalable such that replicas can be added or removed as needed, primarily for auto-scaling. What I'm looking for is either an Istio extension that would support this, or an example Istio extension that I could start with to create such an extension. My thoughts are that when a replica gets a request, if subsequent requests need to come back to that same replica, I'd have the microservice include it's hostname(?) in a response header. The caller would pass that header back in subsequent requests and the extension would notice that header and alter the routing to route the request to the specific replica that needs to receive the request.
I've looked at the consistent hashing mechanism Istio provides, but that won't yield consistent routing as far as I can tell when the number of replicas changes.
Certainly others must have a similar requiremnt.