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https://github.com/heroku/heroku-buildpack-scala
Heroku's buildpack for Scala applications.
https://github.com/heroku/heroku-buildpack-scala
buildpack heroku heroku-languages scala
Last synced: 3 months ago
JSON representation
Heroku's buildpack for Scala applications.
- Host: GitHub
- URL: https://github.com/heroku/heroku-buildpack-scala
- Owner: heroku
- License: mit
- Created: 2011-05-16T21:41:09.000Z (over 13 years ago)
- Default Branch: main
- Last Pushed: 2024-06-21T15:11:13.000Z (7 months ago)
- Last Synced: 2024-06-22T07:46:31.358Z (7 months ago)
- Topics: buildpack, heroku, heroku-languages, scala
- Language: Shell
- Homepage: https://devcenter.heroku.com/articles/scala-support
- Size: 1.53 MB
- Stars: 189
- Watchers: 100
- Forks: 322
- Open Issues: 7
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
- Codeowners: .github/CODEOWNERS
Awesome Lists containing this project
- awesome-cnb - Scala
README
Heroku Buildpack for Scala [](https://github.com/heroku/heroku-buildpack-scala/actions/workflows/ci.yml)
=========================
This is the official [Heroku buildpack](http://devcenter.heroku.com/articles/buildpacks) for Scala apps.
How it works
-----
The buildpack will detect your app as Scala if it has a `project/build.properties` file and either a `.sbt` or `.scala` based build config (for example, a `build.sbt` file). It vendors a version of sbt into your slug (if you are not using sbt-native-packager, it also includes your popluated `.ivy/cache` in the slug). The `.ivy2` directory will be cached between builds to allow for faster build times.
It is strongly recommended that you use sbt-native-packager with this buildpack instead of sbt-start-script. The latter is deprecated, and will result in exessively large slug sizes.
Documentation
------------
For more information about using Scala and buildpacks on Heroku, see these articles:
* [Heroku's Scala Support](https://devcenter.heroku.com/articles/scala-support)
* [Play Documentation: Deploying to Heroku](https://playframework.com/documentation/2.3.x/ProductionHeroku)
* [Customizing the JDK](https://devcenter.heroku.com/articles/customizing-the-jdk)
* [Running a Remote sbt Console for a Scala or Play Application ](https://devcenter.heroku.com/articles/running-a-remote-sbt-console-for-a-scala-or-play-application)
* [Using Node.js to perform JavaScript optimization for Play and Scala applications](https://devcenter.heroku.com/articles/using-node-js-to-perform-javascript-optimization-for-play-and-scala-applications)
* [Reducing the Slug Size of Play 2.x Applications](https://devcenter.heroku.com/articles/reducing-the-slug-size-of-play-2-x-applications)
Examples
------------
There are a number of example applications that demonstrate various ways of configuring a project for use on Heroku. Here are a few:
* [Play Database seed](https://github.com/mkbehbehani/play-heroku-seed)
* [Play Silhouette Angular seed](https://github.com/mohiva/play-silhouette-angular-seed)
* [Minimal sbt example](https://github.com/kissaten/sbt-minimal-scala-sample)
* [Lift example](https://github.com/kissaten/lift-2.5-sample)
Customizing
-----------
This buildpack uses [sbt-extras](https://github.com/paulp/sbt-extras) to run sbt.
In this way, the execution of sbt can be customized either by setting
the SBT_OPTS config variable, or by creating a `.sbtopts` file in the
root directory of your project. When passing options to the underlying
sbt JVM, you must prefix them with `-J`. Thus, setting stack size for
the compile process would look like this:
```
$ heroku config:set SBT_OPTS="-J-Xss4m"
```
Running additional tasks before the build
----------------
Sometimes, it might be necessary to run additional sbt tasks before a build and deployment (for example, database migrations). Ideally, the tasks should be interdependent such that these tasks run automatically as pre-requisities to `compile stage`, but sometimes this might not be the case. To add any additional tasks, set the environment variable `SBT_PRE_TASKS` to a list of tasks that should be executed. If the following is set:
SBT_PRE_TASKS=flyway:migrate info
Then, the following command will be run for build:
sbt flyway:migrate info compile stage
Clean builds
------------
In some cases, builds need to clean artifacts before compiling. If a clean build is necessary, configure builds to perform clean by setting `SBT_CLEAN=true`:
```sh-session
$ heroku config:set SBT_CLEAN=true
Setting config vars and restarting example-app... done, v17
SBT_CLEAN: true
```
All subsequent deploys will use the clean task. To remove the clean task, unset `SBT_CLEAN`:
```sh-session
$ heroku config:unset SBT_CLEAN
Unsetting SBT_CLEAN and restarting example-app... done, v18
```
Development
-------
To make changes to this buildpack, fork it on Github. Push up changes to your fork, then create a new Heroku app to test it, or configure an existing app to use your buildpack:
```
# Create a new Heroku app that uses your buildpack
heroku create --buildpack
# Configure an existing Heroku app to use your buildpack
heroku buildpacks:set
# You can also use a git branch!
heroku buildpacks:set #your-branch
```
License
-------
Licensed under the MIT License. See LICENSE file.