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Deploy Rust applications

Overview

Rust is a system programming language that runs blazingly fast, prevents segfaults, and guarantees thread safety. You can build Rust web services with frameworks like Actix or Iron.

Clever Cloud allows you to deploy Rust web applications. This page will explain you how to set up your application to run it on our service.

Create an application on Clever Cloud

via the web console

  1. Create a new app by clicking on the Add an Application button, in the sidebar.
  2. Select a brand new instance (or a repository from GitHub if your account is linked).
  3. Then select Rust in the platform list.
  4. Configure your scaling options.
  5. Enter your application’s name and description and click “Next”. You can also select the region you want (North America or Europe).

Refer to https://www.clever-cloud.com/doc/getting-started/ for more details on application creation via the console.

via the Clever Tools CLI

  1. Make sure you have clever-tools installed locally. Report to https://www.clever-cloud.com/doc/reference/clever-tools/getting_started/
  2. In your code folder, do clever create --type <type> <app-name> --region <zone> --org <org> where type is the type of technology you rely on, app-name the name you want for your application, zone deployment zone (par for Paris and mtl for Montreal), and org the organization ID the application will be created under.

Refer to https://www.clever-cloud.com/doc/reference/clever-tools/create/ for more details on application creation with Clever Tools.

Setting up environment variables on Clever Cloud

With the Clever Cloud console

  1. Go to the Clever Cloud console, and find the app you want to fine tune under it’s organization.
  2. Find the Environment variables menu and select it.
  3. In this menu, you will see a form with VARIABLE_NAME and variable value fields. Fill them with the desired values then select Create.

With the Clever Tools CLI

  1. Make sure you have clever-tools installed locally. Report to https://www.clever-cloud.com/doc/reference/clever-tools/getting_started/
  2. In your code folder, do clever env set <variable-name> <variable-value>

Refer to https://www.clever-cloud.com/doc/reference/reference-environment-variables/ for more details on available environment variables on Clever Cloud. You can of course create custom ones with the interface we just demonstrated, they will be available for your application.

Configure your Rust application

Mandatory configuration

Be sure that:

  • you have pushed in master branch
  • you listen on port 8080
  • you have committed Cargo.lock
  • you have at least one binary target in Cargo.toml

The result of cargo build --release --locked must be an executable which starts a web server listening on 0.0.0.0:8080.

For instance, a minimal iron application can look like this:

extern crate iron;

use iron::prelude::*;
use iron::status;

fn main() {
    fn hello_world(_: &mut Request) -> IronResult<Response> {
        Ok(Response::with((status::Ok, "Hello World!")))
    }

    let _server = Iron::new(hello_world).http("0.0.0.0:8080").unwrap();
    println!("On 8080");
}

Multiple binary targets

If your Cargo.toml defines multiple targets, you must specify the one you want to run, with the CC_RUST_BIN environment variable. If CC_RUST_BIN is specified, then the executable produced by this target is used to start the application.

Dependencies

Make sure to list all your dependencies in Cargo.toml. For the example above, you need:

[package]
name = "my-app"
version = "0.1.0"
authors = []

[dependencies] iron = "0.4.0"

Cached dependencies

Enabling dependencies caching

You can enable dependencies caching by adding the CC_CACHE_DEPENDENCIES=true environment variable in your application. It is enabled by default only for rust and haskell applications.

Disabling dependencies caching

You can disable dependencies caching completely by removing the CC_CACHE_DEPENDENCIES environment variable from the Clever Cloud console, in the Environment variables menu of your application. Or by setting it to CC_CACHE_DEPENDENCIES=false To fully remove cached dependencies, you have to rebuild your application from scratch. You can select “rebuild and restart” from the Clever Cloud console or launch clever restart --without-cache with the Clever Tools CLI.

Private dependencies

If you use dependencies on a private git repository inside your project, it needs a bit of configuration until this cargo issue has been resolved.

First, you need to use the HTTPS url as the git url for your dependency in your Cargo.toml:

private-dep = { git = "https://GitHub.com/user/my-private-dep.git" }

Then, you need to create a personal access token. It allows to not use your password:

Once you have the token, we need to tell Git to use a credential store. For that, we are going to create it.

Create a clevercloud/pre-build.sh file at the root of your application and paste:

#!/usr/bin/env bash

git config --global credential.helper store
echo "https://${GIT_USERNAME}:${GIT_PASSWORD}@gitlab.com" > ~/.git-credentials
chmod 600 ~/.git-credentials

If you have multiple private repositories, add them accordingly.

Now, go into the environment variables page of your application and create those environment variables:

  • GIT_USERNAME: your GitHub / gitlab / other username
  • GIT_PASSWORD: your GitHub / gitlab / other password
  • CC_PRE_BUILD_HOOK: clevercloud/pre-build.sh
  • CC_POST_BUILD_HOOK: rm /home/bas/.git-credentials

This adds the git configuration before the build start and it cleans it after the build has been done.

Rust channels

By default, your application is built with the latest stable rust version. If you require beta, nightly or a specific Rust version, you can set CC_RUSTUP_CHANNEL environment variable value to beta, nightly or a specific version (eg. 1.36.0). The build uses rustup to select the Rust version you need.

Cargo features

You can enable specific features for your crate by settings the CC_RUST_FEATURES environment variable to the list of features to enable.

To access environment variables from your code, just get them from the environment with std::env::var(<KEY_NAME>).

If some environment variables are critical to your application, here is an approach you can use:

use std::env;

fn main() {
    let my_config_value = env::var("MY_VAR").expect("Missing env var `MY_VAR`");

    something_that_runs_a_web_server(my_config_value);
}

This loads the environment variable in your main function and use .expect to fail early. This way, the application will refuse to start with an helpful error message if MY_VAR is not defined.

Git Deployment on Clever Cloud

You need git on your computer to deploy via this tool. Here is the official website of Git to get more information: git-scm.com

Setting up your remotes

  1. The “Information” page of your app gives you your git deployment URL. It looks like this: git+ssh://git@push.clever-cloud.com/<your_app_id>.git. Copy it in your clipboard.

  2. Locally, under your code folder, type in git init to set up a new git repository or skip this step if you already have one.

  3. Add the deploy URL with git remote add <name> <your-git-deployment-url>.

  4. Add your files via git add <files path> and commit them via git commit -m <your commit message>.

  5. Now push your application on Clever Cloud with git push <name> master

Refer to https://www.clever-cloud.com/doc/getting-started/quickstart/ for more details on git deployments.

Deployment Video

Linking a database or any other add-on to your application

By linking an application to an add-on, the application has the add-on environment variables in its own environment by default.

On add-on creation

Many add-ons do exist on Clever Cloud, please refer to the full list and check add-ons dedicated pages for full instructions.

During add-on creation, you will see Applications screen, with a list of your applications. You can toggle the button to Link and click next. If you finish the process of add-on creation, the application will automatically be linked to it.

Add-on already exists

In the Clever Cloud console, under the Service Dependencies menu of your application, you can use the Link addons dropdown menu to select the name of the add-on you want to link and use the add button to finish the process.

You can also link another application from the same page in the Clever Cloud console, using the Link applications dropdown menu.

More configuration

Need more configuration? To run a script at the end of your deployment? To add your private SSH key to access private dependencies? Go check the Common configuration page.

You may want to have an advanced usage of your application, in which case we recommend you to read the Administrate documentation section.

If you can’t find something or have a specific need like using a non supported version of a particular software, please reach out to the support.

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