Elixir

Overview

Clever Cloud supports Elixir based applications.

Create an application on Clever Cloud

With the web console

Refer to Quickstart for more details on application creation via the console.

With the Clever Tools CLI

1. Make sure you have clever-tools installed locally or follow our CLI getting started guide.
2. In your code folder, do clever create --type <type> <app-name> --region <zone> --org <org> where :
   1. type is the type of technology you rely on
   2. app-name the name you want for your application,
   3. zone deployment zone (par for Paris and mtl for Montreal)
   4. org the organisation ID the application will be created under.

Refer to clever 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 organisation.
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.
4. Fill them with the desired values then select Add.
5. Don’t forget to “Update Changes” at the end of the menu.

With the Clever Tools CLI

1. Make sure you have clever-tools installed locally. Refer to our CLI getting started.
2. In your code folder, do clever env set <variable-name> <variable-value>

Refer to environment variables reference 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 Elixir application

Mandatory configuration

Get your Elixir version in your console with $ elixir -v and set the environment variable CC_ELIXIR_VERSION to its value. Available versions as of today are the following:

The end-of-life (EOL) versions are marked as such.

Compatibility between Elixir and Erlang/OTP

• Each version of Elixir uses the most recent compatible version of Erlang, based on the compatibility table provided in the official Elixir documentation.

If you deploy a Phoenix application

• Edit the file config/prod.secret.exs to replace System.get_env("DATABASE_URL") with System.get_env("POSTGRESQL_ADDON_URI").
• Generate a secret token with $ mix phx.gen.secret.
• set environment variable SECRET_KEY_BASE to the value obtained with $ mix phx.gen.secret previously
• set environment variable CC_PHOENIX_RUN_ECTO_MIGRATE to true if you need to trigger the command $ mix ecto.migrate

Build, deployment phases and custom configuration

Once you push your code to Clever Cloud, the following commands are run:

mix deps.get
mix deps.compile
npm install

These commands will compile your dependencies at the root of your project folder. If you want to use another folder for npm install, specify it via the environment variable CC_PHOENIX_ASSETS_DIR. To change the folder for the entire build / run process, you should use APP_FOLDER environment variable.

Then mix compile is run. If you want to override this behavior, you can set the environment variable CC_MIX_BUILD_GOAL to the value you desire.

At this point, there is the command npm run deploy.

Then mix phx.digest is run. You can override this one with the variable CC_PHOENIX_DIGEST_GOAL.

Finally, mix phx.server is invoked, and as always, you can override this behavior, either with CC_RUN_COMMAND where you have to specify the full command, or CC_PHOENIX_SERVER_GOAL where it will be a mix task by default.

Note: If you need to specify the timezone of your application, you can do it with the variable TZ set to the usual timezone format, for instance Europe/Paris.

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:

   1. git+ssh://git@push.clever-cloud.com/<your_app_id>.git
   2. 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 git deployments for more details.

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: refer to the full list and check add-ons dedicated pages for full instructions.

During add-on creation, an Applications screen appears, 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 is automatically 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 add-ons 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.

Enable health check during deployment

The healthcheck allows you to limit downtimes. Indeed, you can provide Clever Cloud with paths to check. If these paths return something other than 200, the deployment will fail.

Add one (or several) environment variable as such:

CC_HEALTH_CHECK_PATH=/my/awesome/path

Or

CC_HEALTH_CHECK_PATH_0=/my/awesome/path
CC_HEALTH_CHECK_PATH_1=/my/other/path

The deployment process checks all paths. All of them must reply with a 200 OK response code.

By default, when no environment variable (for ex: APP_HOME) is defined, the monitoring checks your repository root path /.

Example

Using the path listed above, below are the expected logs:

Response from GET /my/awesome/path is 200
Response from GET /my/other/path is 500
Health check failed:
- GET /my/other/path returned 500.
If the deployment fails after this message, please update your configuration and redeploy.

In this example, the first path is OK, but the second one failed. This gives you a hint on what failed in your application.

Best practice for healthcheck endpoints

To make the most of a healthcheck endpoint, have it check your critical dependencies. For example:

• execute SELECT 1 + 1; on your database
• retrieve a specific Cellar file
• ping a specific IP through a VPN

Request Flow: Varnish, Redirection.io, custom proxy

Request Flow automatically chains reverse proxies between port 8080 (public) and your application, managing port allocation with no manual configuration. Supported services are activated by their presence in your project:

• Otoroshi Challenge: set OTOROSHI_CHALLENGE_SECRET
• Varnish: add a clevercloud/varnish.vcl file or set CC_VARNISH_FILE
• Redirection.io: set CC_REDIRECTIONIO_PROJECT_KEY

All three can be active simultaneously. To control the order, set CC_REQUEST_FLOW (e.g. redirectionio,varnish). To add a custom middleware, include custom in the chain and define CC_REQUEST_FLOW_CUSTOM with @@LISTEN_PORT@@ and @@FORWARD_PORT@@ placeholders. To block public access, set CC_REQUEST_FLOW=block.

When at least one middleware is active, your application must listen on port 9000 instead of 8080.

• Learn more about Request Flow
• Learn more about Varnish on Clever Cloud
• Learn more about Redirection.io