kuon
I wrote a NIF which have function that can take a long time to run. To prevent the scheduler from being overloaded with long running functions (even if marked at dirty), I made my NIF threaded and it sends message back to erlang using enif_send.
I want to make those call synchronous from a “programmer point of view”. Similar to a Process.sleep() call.
I was wondering what was the best approach. To avoid messing with the caller message inbox and to have an isolated process to receive the message, I thought of using something like this:
task = Task.async(fn ->
call_nif(self())
receive do
<wait for nif response>
end
end)
Task.await(task)
Would that be a good approach?
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krasenyp
It could work but in my opinion it’s best to use a yielding NIF or spawn an extra process and use local means of communication.
kuon
My NIF is blocking and it is hard to make it non blocking, so I wrapped the entire function into a C thread, my NIF now spawn the thread and return immediately, then the thread sends the message. It seems to be a recommenced architecture in the documentation.
Now my question is more about the user API which I want to make synchronous for API simplificy sake, so I thought of this task trick (which works fine). But I was wondering it was the right approach or if there was a more idiomatic way to do it.
In fact it is to make an async call synchronous in general, not really tied to a nif.
benwilson512
Why wrap it in a task at all? Can you simply have a function that calls the NIF and then does a receive right after?
What does this NIF do btw? How long does it run?
kuon
The calling process might have other messages in its inbox when I call this function, I didn’t want to mess with that. This nif does some GPU inference, it runs for about 5 seconds.
I know it could/should be an external port, but using nif I get all serialize/deserialize for free and it is very practical.
LostKobrakai
Namespacing and a selective receive would to that.
kuon
So I can just do
receive do {:my_namespace, …} → <we are done> endand it will not mess with the inbox? I wasn’t sure of that.LostKobrakai
I’ll remove the matches message from the inbox – but it’ll leave anything else as is.