This is a toy async runtime and minimal HTTP server written in Rust as a project to learn about async runtimes and io-uring.
The project was written by Peter Malmgren and Evan Schwartz while participating in the Recurse Center's programmer retreat.
The Runtime consists of the:
- Executor, which runs Futures from a queue of pending Tasks
- Reactor, which submits I/O operations to the kernel using io-uring and reacts to completion events
io-uring uses two ring buffers shared between the userspace code and the kernel in order to submit I/O calls and handle the results. The Runtime is single-threaded because the ring buffers cannot be safely modified by multiple threads without wrapping them in a mutex, which would degrade performance.
While the runtime is single-threaded, the HTTP Server is multi-threaded. It uses one thread (with its own runtime and io-uring buffers) to accept incoming TCP connections and it uses the other threads (also with their own runtimes) to handle requests on those connections.
This project takes inspiration from tokio-uring's design document and the Rust Async Book's chapter on building an executor. The project also uses the io-uring crate's Rust bindings for io-uring.