Deploy Scala and Play Applications to Heroku from Jenkins CI

Last updated 21 January 2020

In addition to Git deployment, Heroku supports direct deployment of prepackaged standalone web applications using the Platform API.

Deploying a prepackaged Scala, Play or sbt application can be done from the command line, but most Scala developers will want to build and run tests from a stable and isolated environment – such as a CI server like Jenkins. In this article, you’ll learn how to configure Jenkins to automatically build an sbt project and deploy it to Heroku.

Creating a Scala application

To begin, we’ll need a simple Scala or Play web application built with sbt. You can use a project of your own, or start with a template by forking the heroku-jenkins-scala-example repository on GitHub. This project contains a simple build.sbt and a single service. Once the project is forked, clone it to your local machine with git.

Next, create a Heroku application for the project. Install the Heroku CLI and run the create command with the -n flag, which will prevent it from adding a Git remote.

$ heroku create
Creating obscure-sierra-7788... done, stack is heroku-18
http://obscure-sierra-7788.herokuapp.com/ | git@heroku.com:obscure-sierra-7788.git

Remember the name Heroku assigns to your application (in this case obscure-sierra-7788), we’ll need it in a moment.

Adding the Heroku sbt plugin

The Heroku sbt plugin adds a deployHeroku task to your application. This mechanism for deployment does not rely on pushing to a remote Git repository, but instead builds an archive of your application locally, and pushes it to the Heroku server using the Platform API.

To use the plugin, add the following code to your project/plugins.sbt file:

addSbtPlugin("com.heroku" % "sbt-heroku" % "2.1.4")

If you’re not using Play, then you’ll also need to add the sbt-native-packager plugin to this file. It provides a stage task, which is required for packaging your application.

Next, add something like this to your build.sbt, but replace “obscure-sierra-7788” with the name of the application you created a moment ago.

herokuAppName in Compile := "obscure-sierra-7788"

Now we’re ready to deploy! Run the following command:

$ sbt stage deployHeroku
...
[info] -----> Packaging application...
[info]        - app: obscure-sierra-7788
[info]        - including: target/universal/stage/
[info] -----> Creating build...
[info]        - file: target/heroku/slug.tgz
[info]        - size: 30MB
[info] -----> Uploading slug... (100%)
[info]        - success
[info] -----> Deploying...
[info] remote:
[info] remote: -----> Fetching custom tar buildpack... done
[info] remote: -----> JVM Common app detected
[info] remote: -----> Installing OpenJDK 1.8... done
[info] remote: -----> Discovering process types
[info] remote:        Procfile declares types -> console, web
[info] remote:
[info] remote: -----> Compressing... done, 78.9MB
[info] remote: -----> Launching... done, v6
[info] remote:        https://obscure-sierra-7788.herokuapp.com/ deployed to Heroku
[info] remote:
[info] -----> Done
[success] Total time: 90 s, completed Aug 29, 2014 3:36:43 PM

Your application will now be running on heroku. You can open it with this command:

$ heroku open -a obscure-sierra-7788

Before we move on, commit all of your changes and push them up to your GitHub repository like so:

$ git commit -am "added heroku plugin"
$ git push origin master

You can use the sbt plugin to deploy just as you might use git push with the repository based deployment strategy. But the plugin is an excellent fit with a CI server. For more information on configuring and using Jenkins, see the Jenkins documentation and wiki.

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