Scala

Overview

Clever Cloud allows you to deploy Scala (and Java) applications built with SBT. This document will explain you how to set up your app to run it on our service.

If you’re looking to deploy a Play Framework application, you can have a look at our dedicated deployment guide for play framework 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 organization 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 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.
  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 Scala application

Mandatory configuration

Your application has to listen on port 8080 for worldwide connections (0.0.0.0). We set the system variable http.port to 8080 for you so in many cases (like for play applications) you don’t have anything to do. You need to use the sbt-native-packager in your project.

The sbt-native-packager

We rely on sbt-native-packager to run applications. This plugin provides a stage task which is run during deployment.

If your project doesn’t already use sbt-native-packager, you need to add it to project/plugins.sbt. Please make sure you use an up-to-date version.

In project/plugins.sbt:

addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % "1.7.0")

Then you need to configure the package type:

In build.sbt:

enablePlugins(JavaAppPackaging)

# Disable javadoc packaging
mappings in (Compile, packageDoc) := Seq()

For more information, please have a look at the documentation for sbt-native-packager

Custom sbt goal

By default, the deployment system execute sbt stage and runs the first binary found into /target/universal/stage/bin. If you want to run another goal, you can specify it with the SBT_DEPLOY_GOAL environment variable.

Multi-module build

If you have a single repository with multiple modules or want to build a specific module in a monorepo (and no top-level stage task), then you can specify the sbt task with SBT_DEPLOY_GOAL.

CC_SBT_TARGET_DIR must be set to the relative path of the module and CC_SBT_TARGET_BIN to the name of the binary to run.

For instance, if you want to deploy a module named service1 that produce a binary named “my-binary”, you have to define the following variables:

SBT_DEPLOY_GOAL=service1/stage
CC_SBT_TARGET_DIR=service1
CC_SBT_TARGET_BIN=my-binary

Check details on environment variables.

Our engine will execute the sbt service1/stage and will run service1/target/universal/stage/bin/my-binary

Note: even when CC_RUN_COMMAND is configured CC_SBT_TARGET_DIR and CC_SBT_TARGET_BIN should be set to the correct values.

HOCON users

If you’re using HOCON configuration files, then you can have direct acces to environment variables from the configuration file:

application.secret=${APPLICATION_SECRET}

Monitor your application with New Relic

You can use New Relic to monitor your application on Clever Cloud.

Please refer to our New Relic documentation to configure it for your application.

Environment injection

Clever Cloud injects environment variables from your application settings as mentioned in setting up environment variables and is also injecting in your application production environment, those from your linked add-ons.

Custom build configurations

On Clever Cloud you can define some build configuration: like the app folder to deploy or the path to validate your application deployment is ready To do that follow the documentation here and add the environement variable you need.

To access environment variables from your code, just get them from the environment with System.getenv("MY_VARIABLE"). Be aware that it can return null.

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 us with paths to check. If these paths return something other than 200, we will consider the deployment as failed.

All you need is 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 will check all given paths. All of them must reply with a 200 OK response code.

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 1st path is OK, but the 2nd one failed. This give you a hint on what failed in your application.

Best practice for healthcheck endpoints

To make the most of a healthcheck endpoint, you should 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
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