Run an Axum App

Getting an application running on Fly.io is essentially working out how to package it as a deployable image. Once packaged, it can be deployed to the Fly.io platform.

In this guide we’ll learn how to deploy an Axum application on Fly.io.

Axum is a web application framework that focuses on ergonomics and modularity.

Deploying an Axum app on Fly.io is really straightforward! With the help of the cargo chef, we get great build times and small images.

Speedrun

First, install flyctl, the Fly.io CLI, and sign up to Fly.io if you haven’t already.

The fastest way to get a basic Axum server on Fly.io is to use our axum template:

git clone --single-branch --branch axum git@github.com:superfly/rust-templates.git axum-app
cd axum-app
fly launch --generate-name

Deploy an Axum App from scratch

If you don’t already have an existing Axum application, you can create one with cargo:

cargo new axum-on-fly
cd axum-on-fly

Then we have to add some dependencies to the project:

cargo add axum
cargo add tokio -F macros -F rt-multi-thread

Now, let’s create a simple Axum app in src/main.rs:

use axum::{routing::get, Router};

#[tokio::main]
async fn main() {
    let app = Router::new().route("/", get(|| async { "Hello from fly.io!" }));
    let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

This will display a “Hello from fly.io!” message when you visit the root URL. Take note that we serve the app on port 8080.

We can confirm everything works fine by running cargo run and checking out http://localhost:8080.

And with that you can deploy the app!

fly launch

Scanning source code
Detected a Axum app
Warning: This organization has no payment method, turning off high availability
Creating app in [redacted]/axum-on-fly
We're about to launch your app on Fly.io. Here's what you're getting:

Organization: Your Name              (fly launch defaults to the personal org)
Name:         [app-name]             (derived from your directory name)
Region:       Amsterdam, Netherlands (this is the fastest region for you)
App Machines: shared-cpu-1x, 1GB RAM (most apps need about 1GB of RAM)
Postgres:     <none>                 (not requested)
Redis:        <none>                 (not requested)
Sentry:       false                  (not requested)

...

==> Building image
...
==> Building image with Docker
...

Watch your deployment at https://fly.io/apps/[app-name]/monitoring
...

Visit your newly deployed app at https://[app-name].fly.dev/

This will generate a fly.toml file with the configuration for your app and a Dockerfile that uses cargo chef. Refer to the fly.toml docs for more configuration options.

To deploy a new version of your app, simply run fly deploy in the project directory.

You can check out the full (yet minimal) example in this GitHub repository for a reference.