1. Examples
  2. Tower

Hello world!

Simple ‘Hello world’ app using Tower.

Create a new directory (mkdir) and move into it (cd) — afterwards, execute the following command to initialize shuttle inside with the Tower boilerplate.

cargo shuttle init --tower

Make sure that your Cargo.toml file looks like the one below — having the right dependencies is key!

Cargo.toml
[package]
name = "hello-world"
version = "0.1.0"
edition = "2021"

[lib]

[dependencies]
hyper = { version = "0.14", features = ["full"] }
shuttle-service = { version = "0.9.0", features = ["web-tower"] }
tower = { version = "0.4", features = ["full"] }

Your lib.rs should look like this:

lib.rs
use std::convert::Infallible;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

#[derive(Clone)]
struct HelloWorld;

impl tower::Service<hyper::Request<hyper::Body>> for HelloWorld {
    type Response = hyper::Response<hyper::Body>;
    type Error = Infallible;
    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send + Sync>>;

    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        Poll::Ready(Ok(()))
    }

    fn call(&mut self, _req: hyper::Request<hyper::Body>) -> Self::Future {
        let body = hyper::Body::from("Hello, world!");
        let resp = hyper::Response::builder()
            .status(200)
            .body(body)
            .expect("Unable to create the `hyper::Response` object");

        let fut = async { Ok(resp) };

        Box::pin(fut)
    }
}

#[shuttle_service::main]
async fn tower() -> Result<HelloWorld, shuttle_service::Error> {
    Ok(HelloWorld)
}

Finally, to deploy your app, all you need to do is:

cargo shuttle deploy

And your app is live! 🎉🎉🎉