Reading what you wrote here - I think this is confirming my looming suspicion. Which is that there is no standard today for upgrading docker containers. Since upgrades happen app to app. For example if I have a docker-compose deployment and service A is lemmy, and service B is postgres the app in this case service A will have to have its own logic for handling upgrades or code migrations.
In other words, the upgrade process can depend on how the software developer writes the software; independent of docker/k8s/vm's or whatever deployment strategy you are running.
I think what I was hoping for was that I'd ask if there was a newer smooth standardized way to do software upgrades besides A/B testing or staggered rollouts but I'm not really seeing that.
I'm not super familiar with Lemmy's codebase but it looks like they're using diesel ORM here and have migration handling on a case by case basis for some major changes. https://github.com/LemmyNet/lemmy/blob/main/src/code_migrations.rs**********___**