When I started working at Clever Cloud, I spent some time messing around with the platform and its tooling. This blog post will present you how I managed to:

• create a simple Scala/Akka HTTP template application with PostgreSQL persistence
• link the application to a managed PostgreSQL
• deploy it
• try it!

Create a Scala/Akka HTTP template 🔨

Get the sources

Clone the project generated from Akka Github quick start template.

This service provides the ability to manage a simple in-memory user registry exposing 4 routes:

• List all users
• Get a specific user
• Create a user
• Delete a user

A thorough description of available the cURL commands may be found here.

Add extra features

A few functionalities have been added on top of the original example:

• store the registry into a PostgreSQL database (instead of in memory)
• read database parameters from environment variables
• add a hardcoded basic authentication

All parameters may be specified in the application.conf file:

• basic auth
• database parameters

Parameters are fetched from environment variables, or the specified default value if none is found

app {
  basic-auth {
    user = "foo"
    user = ${?BASIC_AUTH_USER}
    password = "bar"
    password = ${?BASIC_AUTH_PASSWORD}
  }
  routes {
    # If ask takes more time than this to complete the request is failed
    ask-timeout = 5s
  }

  db {
    host = "localhost"
    host = ${?POSTGRESQL_ADDON_HOST}
    port = "5432"
    port = ${?POSTGRESQL_ADDON_PORT}
    database = "postgres"
    database = ${?POSTGRESQL_ADDON_DB}
    user = "login"
    user = ${?POSTGRESQL_ADDON_USER}
    pass = "pass"
    pass = ${?POSTGRESQL_ADDON_PASSWORD}
  }
}

Run the application using Clever Cloud CLI 🚀

Create a Clever Cloud application

clever create --type sbt myakka --region par --org testorg

This command creates a new application

• of type sbt for Scala
• named myakka
• in Paris region
• inside my test organisation testorg

Enable a dedicated build instance for faster build (optional pro tip)

By default a newly created application will run an XS instance which are quite small for building Scala applications fast. One way to build faster is to use a dedicated build Instance: In the Clever Cloud console, got to your application -> options, and check the box [] Enable dedicated build instance This way you can keep your XS instance for running the application, but you can choose an XL for the build time. Or with the command line tool:

clever scale -a myakka --build-flavor XL

Create a PostgreSQL database

clever addon -l myakka create postgresql-addon myakkadb

This command orders a PostgreSQL add-on instance and link it to myakka, injecting the right environment variables into the application instance to contact the database.

Database creation and migration is performed using flywaydb tool. Those script may be found in the migration/db directory of the application resources.

Migration will be automatically called once you specify the proper build hook in the environment variables

CC_POST_BUILD_HOOK with value sbt flywayMigrate

clever env -a myakka set CC_POST_BUILD_HOOK "sbt flywayMigrate"

Configure basic auth environment variables

Basic authentication login and password can be specified as environment variables using the clever env command. If none is found, basic authentication will default to application.conf file values

clever env -a myakka set BASIC_AUTH_USER <YOUR_AUTH_USER>
clever env -a myakka set BASIC_AUTH_PASSWORD <YOUR_AUTH_PASSWORD>

Link your local repo with your Clever Cloud application instance

Retrieve your application id with

clever applications

Then link the local repository to the application (creating a .clever.json file)

clever link app_<UUID>

Deploy

You are now ready to deploy and run your code, just run

clever deploy

You are now able to follow the deployment process until it completes successfully

Your application is running now!

Try it

It's time to experiment with it using curl or your favorite GUI

Add a user

Adapt this command in order to insert a new user into the registry:

curl --request POST \
  --url https://app-<UUID>.cleverapps.io/users \
  --header 'Content-type: application/json' \
  -u '<YOUR_AUTH_USER>:<YOUR_AUTH_PASSWORD>' \
  --data '{
  "name": "Serge",
  "age": 42,
  "countryOfResidence": "Greenland"
}'

{
	"description": "User Serge created."
}

Get all users

Check that the user has been properly created, by getting the list of users:

curl --request GET \
  --url https://app-<UUID>.cleverapps.io/users \
  -u '<YOUR_AUTH_USER>:<YOUR_AUTH_PASSWORD>'

{"users":[{"age":42,"countryOfResidence":"Greenland","name":"Serge"}]}

It works, Success! 🎉

Clever Cloud applications to run your jobs

Enhance your Clever Cloud deployments workflow

pipeline {
  environment {
    CLEVER_TOKEN = credentials('CLEVER_TOKEN')
    CLEVER_SECRET = credentials('CLEVER_SECRET')
  }

  stage('clever-tools') {
      steps {
        script {
          sh 'npm install -g clever-tools'
       }
     }
  }

  stage('tests') {
    // Your tests steps
  }

  stage('deployment') {
    steps {
      script {
        // Deploy the application
        // A .clever.json file must exists in the repository
        sh 'clever deploy'
      }
    }
  }
}

Built with the classic features you love

Pricing

What's next?

We've been quietly rolling out support for hooks during deployments. This may come as a surprise if you listen to our ramblings about deployment processes, as we've always pushed for self-contained, zero-adherence builds. Don't worry, we haven't changed our minds. Let's see why and how doing things outside of the build system can make sense.

Our stance is unchanged

At Clever Cloud, we're uncompromizing on automation. The first step to automate production is to have robust, reproducible builds. The best way to be robust and reproducible is to get rid of implicit dependencies: if you have more than two operations to run in sequence to build and run your project, then you have a problem. Not just for deployment, mind you, but for your day-to-day productivity: working on your application becomes complicated, and onboarding new developers takes hours (or worse).

How are Node.JS apps deployed on Clever Cloud? Simple: npm install && npm start. What about scala applications? sbt stage. No problem, no vendor lock-in. That's nice and clean. Unfortunately it's not the whole story.

The case of frontend build

It's got to be the most common question we have about our deployment system: "how can I integrate my frontend build in the deployment phase"?

For Node.JS, easy, just add your build phase to scripts.install. For scala applications, you can configure sbt-web. For PHP applications, you can hook in composer. Hooking the frontend build in the main build can range from super easy to dwarf-fortress-fun. Some build tools allow to run arbitrary code, some are more restrictive (but more predictable). For instance, building Haskell applications with stack makes it quite hard to shell out and run npm install.

Monolithic builds are not the only option

In a full-stack setup (eg Ruby on Rails or Play! framework), integrating the front-end build in the build system is a good idea, as it gives you better integration (eg. play run also refreshes compiled assets). If you're going with a minimalist tech stack however, integrating everything makes less sense, as your needs for the development environment are not aligned with your needs for the production environment. Let's say you work on a scotty web app, with some assets compilation. For development, no need to bake everything in the web lib, you can use Devloop and have automatic recompiling on reload, both for frontend and backend.

In that case, instead of shoehorning the frontend build in a stack setup, using a hook as an escape hatch is the most time-effective way to do it; it also gives you more control on when build tasks happen. This allows you to leverage our build system more efficiently.

Available hooks and when to use them

A complete rundown of hooks is available in the documentation, but I'll give you a concrete example to give you a better understanding of what you can do.

Please give us feedback

I've created the new hooks system to scratch an itch, so it may change a bit in the following months. Please reach out to the support team if you have questions or suggestions.