The dangers of the Single Global Process

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2024-06-09 16:00:10

There are a few things in the Elixir/Erlang ecosystem that I consider required reading. To spawn, or not to spawn? by Saša Jurić is definitely one of them. If you haven’t read it, you need to. It’ll change the way you think about building elixir applications.

That post flipped the elixir communities’ idea of good design on its head and for a good reason. Modeling the domain with pure functions is a powerful approach and one that we should strive for when we can.

But, there was one pattern that emerged that I think has been misapplied as a universal solution. That pattern is what I’ve been calling - for lack of a better name - the “single global process” pattern or SGP for short. You’ve probably seen this pattern. Its the one where you do this elegant, functional domain modeling and then put it in a long-running process somewhere, effectively turning the process into a write-through cache. In Saša’s post, the single process is the RoundServer.

I don’t think Saša intended to promote this pattern. I wasn’t there when he was writing it, but I always thought that using a single RoundServer to manage a round was somewhat incidental. The unique process was an implementation detail, and the critical point was to model your domain with functions.