Pass application.conf file at deploy time in Docker setup built using jar

user_5662691 0
Viewed 395

My requirement is to pass the application.conf file for Play framework based Scala application at deploy time in a Docker setup on Kubernetes, in order to support values passed using secrets. However, the constraint I have is I use the application's fat-jar as entrypoint in the Dockerfile:

...
EXPOSE 9000
ENTRYPOINT java -jar myapp.jar

I want to build the fat-jar with reference to that application.conf which will be passed at deploy time (using secrets), with SBT command, something like:

sbt -Dconfig.file="/opt/myorg/myapp/application.conf" clean publish

But this would fail as the file would only be available at deploy time. How can I achieve this?

docker sbt scala
1 Answers

You should change your deploy so that container takes this file from somewhere or change the approach of getting the needed properties. For example:

  • you can execute ssh/scp command that will copy the file into the container and support this by k8s because by default it will shuffle/recreate containers in the cluster (this is an awful solution, but you can get the idea from it)
  • you can attach the external volume with this file to the container and then pass the path to the java process. Something like that should work ENTRYPOINT java -jar myapp.jar -Dconfig.file="/opt/myorg/myapp/application.conf".
  • add config as a file to the jar at build time (but as I understood build time is not the case)
  • change how your app gets the properties so that it can get them from the env variables, and define env during the deploy process

I'm not a k8s user, so I can't tell you the exact way of doing this. But I hope some of that can help you.

user_140443710
Related