use Task, restart: :permanent
seems not right, IMO. I don’t think statefulness/not statefulness is the right way to think about whether or not you should use a GenServer vs. a Task. There are times where I have GenServer equivalents with state nil.
I would say a GenServer is supposed to be a service, and a Task is supposed to be an action. If you speak a romance language, GenServers are imperfective and Tasks are perfective. Tasks IIRC are a creation of Elixir to give OTP a sane default way to supervise simple things with strictly internal control flow, but as soon as you’re doing message passing to interface with a task, you’re in GenServer territory.
If you are having a Task that is permanent, it must somehow be responding to a message (probably a receive block?). Although that might work for now, I would suggest changing that over to a GenServer call. If for no other reason than the caller will know if the somehow the GenServer is unavailable. Even if all your call does is reply :ok and performs a {:continue, info} to actually do its thing. That will let the GenServer manage your message queue instead of doing it manually. This is good because you’ll get solid error warnings (the calling GenServer will crash), and you’ll also get backpressure management.
If your needed throughput for your service starts go get really high, you’re going to want to do process pools, and buliding out a process pool from a GenServer is a well-trodden, battle-tested, and relatively formulaic process; doing so with a Task I suspect could be challenging.
