My particular problem was a back end for a medium-level multiplayer RPG (500ish people connected at once per world). The only real way I found to get it performant was to lean heavily into processes. But then you have a race condition problem and need to DIY your own method of synchronization because you're no longer using the process mailbox for that purpose.

In practice I haven't found the immutability of Elixir that useful for concurrency because data is deep copied when it goes across processes anyways. This is in comparison to Clojure where you can safely and perfomantly share immutable data across multiple threads.

I would have suggested ets tables + entity system.

From my testing, the performance characteristics of ets isn't that great - data still gets copied around when you access stuff in it. I tried using it in my exploratory tests and certain worst case, player-focused actions would take around 20ms, when using a regular GenServer with a synchronization system on top would take around 5us.

To be clear, for NPCs it worked fine. But players are hoarders and in an RPG that can result in a ridiculous amount of data being attached to them.

I'm an Erlang enthusiast, but find myself writing C for (small) things where I need to interface with struct heavy library calls, and nobody else has built up an BEAMy interface. I could build it, but it would take about the same work to just build my project in C.

Of course, maybe there's a generalized BEAM to C call library I'm not aware of? (I didn't think to search for one until now)

Also, honestly, it's a little easier to have a C daemon than an erlang daemon. Just call daemon() before the service loop vs setting up an app file. Of course, you have to build hotload yourself from dlopen and friends, and you lose out on a lot of features.

Two ideas that might help:

Elixir releases are built in and easy to use. You don't have to write an app file directly for instance.

I usually use ports for C interface (rather than NIFs). I have a little boilerplate C and Elixir that I recycle to do the ground work and then it's just your specific implementation detail.

Yeah, so I'd write just as much (or likely more) C code to interface with the library and BEAM as just writing the implementation in C.

Probably the best you're going to get for a generalized c call library is rustler or zigler (I maintain zigler)

Yeah, so those look like nicer ways to call C than writing a NIF, but they don't look like point to a C include and get the constants and a way to call the functions in the include (and use the types in the include. If I'm reading correctly.

I'm looking for the equivalent of Perl's h2xs, or something like that. (which incidentally, maybe I should be writing these things in perl ;)

challenge accepted: https://github.com/ityonemo/zigler/issues/240