Fun experiment, try and benchmark a simple file download on a simple web server using rocket.rs (which also uses tokio and hyper, and has a built in fileserver type, so just a few lines of code) and compare it to a vanilla nginx config.

Here’s the rocket.rs source I used:

    #[rocket::main]
    async fn main() -> Result<(), rocket::Error> {
        rocket::build()
            .mount("/", rocket::fs::FileServer::from("/tmp/test"))
            .ignite()
            .await?
            .launch()
            .await?;
        Ok(())
    }

And do `mkdir /tmp/test && dd if=/dev/urandom of=/tmp/test/bigfile bs=1G count1` to create a 1G file, and run `time curl -o /dev/null localhost:8000/bigfile`.

My nginx config:

    worker_processes auto;
    master_process off;
    pid /dev/null;

    events {}

    http {
        sendfile on;
        access_log /dev/stdout;
        error_log /dev/stderr;
        server {
            listen 8089;
            server_name localhost;
            root /tmp/test;

            location / {
                try_files $uri $uri/ =404;
            }
        }
    }

launched with `nginx -c "$(pwd)"/nginx.conf -g "daemon off;"`

The results for a 1GB file for me on an nvme ssd, averaged over 100 runs:

    nginx: 150ms
    rocket: 4 seconds

Or roughly 25x slower. Release mode makes no difference.

You can definitely write slow code in rust if you’re naive about reading/writing between channels a few kilobytes at a time, which is what rocket does, vs using sendfile(2), like nginx does.

Edit: These numbers were from a few months ago... I tried it again by just pasting the above into a new project with `cargo init` and adding rocket and tokio to my deps, and it's now 2.3s in debug and 1.2s in release mode. It may have improved since a few months ago, but it's still 10x slower.