ollien
Discovering a task supervisor local to my supervision tree
I was writing a GenServer and quickly discovered the need to generate tasks within this GenServer. This GenServer can not have a globally unique name (as I require many instances of it. I decided to keep the current module structure, changing the GenServer to a Supervisor and spawning my original GenServer as a child of this supervisor (with the Supervisor having public functions that call the child GenServer). Ideally, my supervision tree would look something like this
MyServerSupervisor
/\
/ \
/ \
MyGenServer MyTaskSupervisor
Also, ideally, I would spawn my tasks within MyTaskSupervisor. However, the obvious question arises: how does MyGenServer discover this task supervisor? In other projects, I’ve given this task supervisor a globally unique name, but I can’t do that here.
Looking into the problem, I’ve seen many suggestions to use a Registry, but those require globally unique names. In order to have a registry for my task supervisors, I’d have to spawn the Registry in my root supervisor to ensure all of my processes can find it. It would be a lot nicer if I could somehow register the task supervisor in the context MyServerSupervisor. Is there a way to achieve what I want, or is the closest analog the solution I just described?
Thanks!
First Post!
al2o3cr
Question about naming:
How do you tell these apart? That’s where a Registry would usually come in handy.
For instance, imagine that each instance can be identified by an Erlang term that we’ll call id. Could be a database ID, could be a UUID, could be an ARN, whatever.
Start a single top-level Registry instance, we’ll name it MyServerRegistry for concreteness.
Then instances of MyServerSupervisor would name themselves like:
{:via, Registry, {MyServerRegistry, id}}
While instances of MyGenServer and MyTaskSupervisor could be named like:
{:via, Registry, {MyServerRegistry, id, :server}}
# vs
{:via, Registry, {MyServerRegistry, id, :task_supervisor}}
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