Dockerizing a Scala application is pretty easy. The first concern is creating a fat jar. Now we all come from different backgrounds including maven/gradle and different plugins that handle this issue. If you use sbt the way to go is to use the sbt-assembly plugin.
To use it we should add it to our project/plugins.sbt file. If the file does not exist create it.
logLevel := Level.Warn addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.6")
So by executing
sbt clean assembly
We will end up with a fat jar located at the target/scala-**/**.jar path.
Now the easy part is putting our application inside docker, thus a Dockerfile is needed.
We will use the openjdk alpine as a base image.
FROM openjdk:8-jre-alpine ADD target/scala-**/your-fat-jar app.jar ENTRYPOINT ["java","-jar","/app.jar"]
The above approach works ok and gives the control needed to customize your build process. For a more bootstraping experience you can use the sbt native packager.
All you need to do is to add the plugin to project/plugins.sbt file.
logLevel := Level.Warn addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % "1.3.4")
Then we specify the main class of our application and enable the Java and Docker plugins from the native packager at the build.sbt file.
mainClass in Compile := Some("your.package.MainClass") enablePlugins(JavaAppPackaging) enablePlugins(DockerPlugin)
The next step is to issue the sbt command.
This command will build your application, include the binaries needed to the jar, containerize your application and publish it to your local maven repo.