Docker Entrypoint does not consider mainClass option (and resulted script name)

Expected behaviour

I have a project with multiple main classes and as state here: https://www.scala-sbt.org/sbt-native-packager/archetypes/java_app/index.html#usage I use

mainClass in(Compile, run) := Option("com.<redacted>.Boot")

The scripts in bin result with boot name which I think is to be expected.

Building the docker image for the project I expect the image to start properly.

Actual behaviour

The Entrypoint in the image is wrong, using project name and not considering the given mainClass option.

From docker inspect

ENTRYPOINT [\"/opt/microservice/bin/<project-name>\"]

Information

Plugin version: 1.7.0 SBT: 1.3.10 Built on Linux

Related options:

val dockerSettings = Seq(
  defaultLinuxInstallLocation in Docker := "/opt/microservice",
  dockerRepository in Docker := Some("<docker-registry>"),
  dockerExposedPorts in Docker := Seq(8080),
  // Ignore this, we need to run as root for now
  daemonUser in Docker := "root",
  daemonUserUid in Docker := None,
  version in Docker := version.value
)

[lebenitza]

Thanks for your help!

[muuki88]

Thanks for your patience @MihaiAnei 😅 Of course that’s the issue 🤦

I found the root cause. It’s, as quite a few times, a scoping issue. So the fix ist

// too narrow scope
Comile / run / mainClass := Some("...")

// just about right scope
Compile / mainClass := Some("....") 

the mainClass in (Compile,run) (I used the new syntax in the example above) isn’t used for setting the executableScriptName . So it falls back to the default behaviour.

The default behaviour, generating a script per class, doesn’t work very well with the docker plugin. However I’m fine with that as a docker image ideally as one entry point. IMHO that’s the point of having containers 😜 If you have multiple main classes, then setting the “default” one should be fine.

Thanks again for your help 😗