The main thing I want for Async Rust is the ability to not use it.

What I'm doing involves a virtual world viewer with maybe a dozen threads. Some are compute bound. Some are talking to the GPU. Some are waiting for I/O. The normal situation is about 2 or 3 CPUs of work. Sometimes more.

I don't want an async model, which assumes you're I/O bound, interfering with keeping all those CPUs busy. Already I've had to switch from using "reqwest", which now seems to always bring in tokio, to "ureq", a minimal HTTP client. The way to do HTTP requests used to be with "hyper", but that became a lower level for "reqwest", and then "tokio" was slipped in underneath to make it "async". It always uses async, even if you make a blocking request.

"Async" is a specialized tool for web servers with very large numbers of clients. Outside of that niche, it's seldom needed.

Firstly, `reqwest` exposes both an async and a synchronous API, allowing the developer to choose which one to use. They are largely interchangeable code-wise. [1]

Secondarily, and more broadly, async is possible to opt out of. You must understand that most web and network related libraries will be async by default for performance, because people who write in Rust and people who write web servers typically care greatly about performance. This is the intersection of those two groups. That being said, there are options outside of that ecosystem. [2]

If you truly want to use an asynchronous library without migrating your application to run entirely on an async runtime like tokio, you can run it inside of a synchronous function without much trouble. I've put together a playground link for you. [3]

1. https://docs.rs/reqwest/0.11.2/reqwest/blocking/index.html

2. Iron: https://github.com/iron/iron Rouille: https://github.com/tomaka/rouille

3. https://play.rust-lang.org/?version=stable&mode=debug&editio...