Run a Poem 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 a Poem application on Fly.io.

Poem is a full-featured and easy-to-use web framework with the Rust programming language.

Deploying a Poem app on Fly.io is simple! 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 Poem server on Fly.io is to use our poem template:

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

Deploy a Poem App from scratch

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

cargo new poem-on-fly
cd poem-on-fly

Then we have to add some dependencies to the project:

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

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

use poem::{get, handler, listener::TcpListener, Route, Server};

#[handler]
fn hello() -> String {
    format!("hello from fly.io!")
}

#[tokio::main]
async fn main() -> Result<(), std::io::Error> {
    let app = Route::new().at("/", get(hello));
    Server::new(TcpListener::bind("0.0.0.0:8080"))
        .run(app)
        .await
}

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 Poem app
Warning: This organization has no payment method, turning off high availability
Creating app in [redacted]/poem-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.