actix-website/content/docs/autoreload.md

title	menu	weight
Autoreloading	docs_patterns	1000

Auto-Reloading Development Server

During development it can be very handy to have cargo automatically recompile the code on change. This can be accomplished by using cargo-watch. Because an actix app will typically bind to a port for listening for incoming HTTP requests it makes sense to combine this with the listenfd crate and the systemfd utility to ensure the socket is kept open while the app is compiling and reloading.

systemfd will open a socket and pass it to cargo-watch which will watch for changes and then invoke the compiler and run your actix app. The actix app will then use listenfd to pick up the socket that systemfd opened.

Binaries Necessary

For an automatic reloading experience you need to install cargo-watch and systemfd. Both are written in rust and can be installed with cargo install:

cargo install systemfd cargo-watch

Code Changes

Additionally you need to slightly modify your actix app so that it can pick up an external socket opened by systemfd. Add the listenfd dependency to your app:

[dependencies]
listenfd = "0.3"

Then modify your server code to only invoke bind as a fallback:

extern crate actix_web;
extern crate listenfd;

use listenfd::ListenFd;
use actix_web::{server, App, HttpRequest, Responder};

fn index(_req: &HttpRequest) -> impl Responder {
    "Hello World!"
}

fn main() {
    let mut listenfd = ListenFd::from_env();
    let mut server = server::new(|| {
        App::new()
            .resource("/", |r| r.f(index))
    });

    server = if let Some(l) = listenfd.take_tcp_listener(0).unwrap() {
        server.listen(l)
    } else {
        server.bind("127.0.0.1:3000").unwrap()
    };

    server.run();
}

Running the Server

To now run the development server invoke this command:

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