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Deploy a Rocket App to Heroku

Deploy a Rocket app with an encrypted .env.vault file to Heroku.

Find a complete code example on GitHub for this guide.

Initial setup

Install rocket.

cargo new yourapp
cd yourapp
cargo add rocket

Rocket uses advanced Rust features so install the nightly version of Rust.

rustup override set nightly

Modify src/main.rs file with the web server code.

sr/main.rs

#![feature(proc_macro_hygiene, decl_macro)]

#[macro_use] extern crate rocket;

#[get("/")]
fn index() -> String {
    let hello = std::env::var("HELLO").unwrap_or("".to_string());
    format!("Hello {}.", hello)
}

fn main() {
    rocket::ignite().mount("/", routes![index]).launch();
}

Add a Procfile to run your app on Heroku.

Procfile

web: ROCKET_PORT=$PORT ROCKET_KEEP_ALIVE=0 ./target/release/yourapp

Create a rust-toolchain file to tell Heroku to run the nightly rust version.

rust-toolchain

nightly-2023-11-15

Commit that to code, set the rust buildpack, and push it to Heroku.

heroku create
heroku buildpacks:set emk/rust
git push heroku
yourapp.herokuapp.com

Once deployed, your app will say Hello . as it doesn't have a way to access the environment variable yet. Let's do that next.

Install dotenv-vault

Install dotenv-vault.

cargo add dotenv-vault

Create a .env file in the root of your project.

.env

# .env
HELLO="World"

As early as possible in your main function, load dotenv.

src/main.rs

...

fn main() {
    let _ = dotenv_vault::dotenv();

    rocket::ignite().mount("/", routes![index]).launch();
}

Try running it locally.

cargo run

Rocket has launched from http://localhost:8000

It should say Hello World..

Great! process.env now has the keys and values you defined in your .env file. That covers local development. Let's solve for production next.

Build .env.vault

Push your latest .env file changes and edit your production secrets. Learn more about syncing

npx dotenv-vault@latest push
npx dotenv-vault@latest open production

Use the UI to configure those secrets per environment.

www.dotenv.org

Then build your encrypted .env.vault file.

npx dotenv-vault@latest build

Its contents should look something like this.

.env.vault

#/-------------------.env.vault---------------------/
#/         cloud-agnostic vaulting standard         /
#/   [how it works](https://dotenv.org/env-vault)   /
#/--------------------------------------------------/

# development
DOTENV_VAULT_DEVELOPMENT="/HqNgQWsf6Oh6XB9pI/CGkdgCe6d4/vWZHgP50RRoDTzkzPQk/xOaQs="
DOTENV_VAULT_DEVELOPMENT_VERSION=2

# production
DOTENV_VAULT_PRODUCTION="x26PuIKQ/xZ5eKrYomKngM+dO/9v1vxhwslE/zjHdg3l+H6q6PheB5GVDVIbZg=="
DOTENV_VAULT_PRODUCTION_VERSION=2

Set DOTENV_KEY

Fetch your production DOTENV_KEY.

npx dotenv-vault@latest keys production
# outputs: dotenv://:[email protected]/vault/.env.vault?environment=production

Set DOTENV_KEY on Heroku using the CLI.

heroku config:set DOTENV_KEY='dotenv://:key_1234…@dotenv.org/vault/.env.vault?environment=production'

Or use Heroku's UI.

www.heroku.com

Deploy

Commit those changes safely to code and deploy.

That's it! On deploy, your .env.vault file will be decrypted and its production secrets injected as environment variables‚ just in time.

yourapp.herokuapp.com

You'll know things worked correctly when you see 'Loading env from encrypted .env.vault' in your logs. If a DOTENV_KEY is not set (for example when developing on your local machine) it will fall back to standard dotenv functionality.

heroku logs --tail

You succesfully used the new .env.vault standard to encrypt and deploy your secrets. This is much safer than scattering your secrets across multiple third-party platforms and tools. Whenever you need to add or change a secret, just rebuild your .env.vault file and redeploy.