Suppose I have a reliable actor that registers a reminder in OnActivateAsync. This reminder has a period that is retrieved from some persistent storage. After some time the actor is garbage-collected.
After some more time the actor is called or the reminder fires and OnActivateAsync is called by the runtime. In the meantime, I updated the reminder period in persistent storage.
What happens now? I attempt to register the reminder again but with a different period. Will the reminder be updated with the new period?
Another case is an update of the actor. Suppose the period is hard-coded but a new version of the actor uses a different period. What happens now when OnActivateAsync is called and the reminder is registered again?
When you try to register an existing reminder again, it will be updated. From RegisterReminderAsync documentation (https://learn.microsoft.com/en-us/dotnet/api/microsoft.servicefabric.actors.runtime.actorbase.registerreminderasync?view=azure-dotnet):
Existing reminders can also be updated by calling this method again.