Auto-reloading server

Cargo.toml

[package]
name = "example"
version = "0.1.0"
edition = "2021"

[dependencies]
actix-web = "4.0"
anyhow = { version = "1.0", features = ["backtrace"] }
listenfd = "0.5"
log = "0.4"
simple_logger = "2.1"
tokio = { version = "1.17", features = ["signal"]}
thiserror = "1.0"

cli.sh

cargo install systemfd cargo-watch

# cargo-watch builds and runs the application on code change
# and systemfd sets up a socket to handoff to the application at startup

systemfd --no-pid --socket http::3000 -- cargo watch -x run

main.rs

use actix_web::{get, middleware, App, HttpServer};
use anyhow::{Error, Result};
use listenfd::ListenFd;
use log::debug;
use simple_logger::SimpleLogger;

#[get("/")]
async fn hello() -> &'static str {
    debug!("👋 yo");
    "👋 yo ho ho and a bottle of rum"
}

#[actix_web::main]
async fn main() -> Result<()> {
    SimpleLogger::new()
        .with_level(log::LevelFilter::Warn)
        .init()?;

    let mut listenfd = ListenFd::from_env();
    let listener = listenfd.take_tcp_listener(0)?.unwrap();

    HttpServer::new(move || {
        App::new()
            .wrap(middleware::Logger::default())
            .service(hello)
    })
    .listen(listener)?
    .run()
    .await
    .map_err(Error::from)
}