Building a Distributed Turn-Based Game System in Elixir

Summary

Mark Ericksen describes building a proof-of-concept distributed, clustered game system for turn-based multiplayer applications with Elixir and Phoenix LiveView. Rather than separate JavaScript and API layers or external state systems such as Kafka and Redis, the design uses server-rendered HTML over websockets, Phoenix.PubSub, and Horde’s distributed process registry. A player’s LiveView sends moves to a GameServer, which publishes updated game state so subscribed LiveViews re-render for every connected player; Tic-Tac-Toe supplies the model. Hosted on Fly.io, geographically close web servers connect over a private WireGuard network while a game’s single GameServer remains the source of truth, with libcluster handling cluster formation and healing. The resulting open-source proof of concept supports multiplayer games, four-letter game codes, on-demand creation, responsive updates, and globally clustered servers.

Takeaways

1. 1

   Phoenix.PubSub distributes updated game state, while Horde provides a distributed process registry for locating and interacting with GameServers.

2. 2

   Fly.io places web servers near users while allowing them to communicate privately with a GameServer running in another region over WireGuard.

3. 3

   The proof of concept supports multiplayer games, four-letter game codes, on-demand game and match creation, responsive updates, and clustered servers.