Alpine based image for sbt-scala

[Carbrex]

Comparison:
docker images

The image eclipse-temurin-jammy-21.0.2_13 with base image eclipse-temurin:21.0.2_13-jdk is 977MB
The new image is 792MB
But moving

# Prepare sbt (warm cache)
RUN \
  sbt sbtVersion && \
  mkdir -p project && \
  echo "scalaVersion := \"${SCALA_VERSION}\"" > build.sbt && \
  echo "sbt.version=${SBT_VERSION}" > project/build.properties && \
  echo "// force sbt compiler-bridge download" > project/Dependencies.scala && \
  echo "case object Temp" > Temp.scala && \
  sbt compile && \
  rm -r project && rm build.sbt && rm Temp.scala && rm -r target

this code to build stage reduces the image size to 552MB (That still works good though I am not sure what will be the downside of moving this to build stage).
Currently this pr has it outside of build stage I will move it to build stage to reduce size if you say so. The link to that branch is https://github.com/Carbrex/docker-sbt/blob/warm-stage-in-build/eclipse-temurin/alpine.Dockerfile

I have also not been able to check for the build.yml changes as I dont know how to run them. Your help would be appreciated.
Thanks for your time!
Closes #276

[francisdb]

The purpose of that step is to make sure sbt preloads the scala version. Should improve sbt project load time. On the other hand if you have a proper ci build cache in place it does not matter so much as it only happens on the first build.
To create a minimal image we could also remove the scala install unless ppl want to use the scalac command.

[Carbrex]

So, what are the changes you want?
Also, I have tried fixing build.yml, though I am still not sure if it will work.

[francisdb]

Looks like the build is still failing

So, what are the changes you want? Also, I have tried fixing build.yml, though I am still not sure if it will work.

What will you be using the image for? Do you want it to be as small as possible and will you only be using sbt?

[Carbrex]

In my specific use case, I am running https://github.com/lichess-org/lila-docker which has atleast 4 images that rely on your sbt-scala images ( namely lila, lila-ws, lila-search and lila-engine). This is the dockerfile for lila-ws. We would still need scala. Since we use four different images, this reduction in size becomes significant.

[Carbrex]

The tests have passed I am now removing carbrex from repository name.

[francisdb]

In my specific use case, I am running https://github.com/lichess-org/lila-docker which has atleast 4 images that rely on your sbt-scala images ( namely lila, lila-ws, lila-search and lila-engine). This is the dockerfile for lila-ws. We would still need scala. Since we use four different images, this reduction in size becomes significant.

Since that docker file only interacts with sbt you don't need the separate scala install.

Looking at lila-ws, this seems to be a runtime container so it would even be better to not use sbt at all and make sure your app can run on a plain jdk docker image. That will avoid sbt loading and code compilation on startup.

Have you considered https://www.scala-sbt.org/sbt-native-packager/formats/docker.html ?

Ok never mind, this seems to be a dev container.

[francisdb]

So you care more about size than startup time?

[Carbrex]

So you care more about size than startup time?

No, I guess the startup time is essential too. I just didn't know by then what the warming stage do.
You don't have to merge it if you dont like the idea of this alpine image.

[francisdb]

I you consider this done I'm OK to merge.

[Carbrex]

Its done on my end.👍

[francisdb]

One more thing, can you remove the JDK 11 build? I plan to remove all those builds as jdk 11 primary support period has ended.

By the way, Lichess is amazing.

[Carbrex]

Ok, I will remove it we don't use it anyway. (Just the alpine one or the other ones too?)

By the way, Lichess is amazing.

I agree, but I am not a maintainer just a contributor.

[francisdb]

Ok, I will remove it we don't use it anyway. (Just the alpine one or the other ones too?)

Just the alpine one

[Carbrex]

Done👍