Chat Room

1st Dec 2024

Serverless chat room using Rust.

I spent a weekend creating a basic chat room as a means to explore API development in Rust and React development in AstroJS.

You can see it in action here.

If anyone else goes to the same URL, they will automatically be connected.

I used a single lambda running Axum that handles all websocket connections ($connect, $disconnect, $default). This is non-standard, the general recommendation is to use a different Lambda for each endpoint. I did this is partly because I wanted to try out a routing library in Rust, but also because its easier to run locally, and it provides flexibility to deploy to a dedicated server if I decided to. I talk about this more in this blog post. The source code for this is here.

Creating a service that has multiple entrypoints (such as from API Gateway and from a local server), or multiple providers (e.g. a local in-memory database or a cloud database) doesn’t feel well supported. Rust “features” didn’t quite fit, it required a full rebuild whenever I changed feature set. Multiple binaries works better, but still needed a few snippets to tell the compiler that “unused code” was okay.

Once it was up and running, I was very happy with the development lifecycle:

• Running locally with a local in-memory database (for fast iteration)
• Running locally using a cloud database (for confirmation of logic & fast debugging)
• Running in the cloud

And happy with the end result

• ~60ms to send a message
• Cold boot once, not once per endpoint
• Reusable structure for future Rust projects