Our catscii program does everything we want it to do, except that it’s a command-line application rather than a web server. Let’s fix that.

Enter axum

The documentation for the axum crate tells us how to make a basic web server, and we honestly don’t need much more than that.

So let’s add axum:

amos@miles:~/catscii$ cargo add axum@0.6 Updating crates.io index Adding axum =0.6 to dependencies. Features: + form + http1 + json + matched-path + original-uri + query + tokio + tower-log - __private_docs - headers - http2 - macros - multipart - w

Falling out of love with warp

Back when I wrote this codebase, warp was the best / only alternative for something relatively high-level on top of hyper.

I was never super fond of warp’s model — it’s a fine crate, just not for me.

The way routing works is essentially building a type that gets larger and larger. One route might look like:

let bye = warp::path("bye") .and(warp::path::param()) .map(|name: String| format!("Good bye, {}!", name));

As the popular saying goes, there are only two hard problems in computer science: caching, off-by-one errors, and getting a Rust job that isn’t cryptocurrency-related.

Today, we’ll discuss caching! Or rather, we’ll discuss… “request coalescing”, or “request deduplication”, or “single-flighting” - there’s many names for that concept, which we’ll get into fairly soon.