Scala config lookup secrets - scala

Question

I have application.conf file which contains secrets(password for DB etc..) And this secret will be mounted as a file(the file content will contain the actual secrets) in the running pod. How can scala config library be tweaked to handle this. i.e
instead of normal application.conf
db {
user = "username"
password = "xxx"
}
I would have something like this...
db {
user = "username"
password = "${file_location}"
}
As the file is parsed, it should identify that the value of key password, needs to be resolved by looking up the file and loading its contents.
A simple function can be written to load the content of this file, how can this is be integrated with seamlessly with scala config. ie. The rest of the code will continue to use
config.getString(db.password)

Answer 1

I assume you are using configuration of HOCON format and Typesafe configuration library for it.
I don't think it has such feature out of the box, but as an possible alternative you can take a look at include feature - you can include content of another file into your application.conf:
db {
user = "username"
}
include /path/to/pod.conf //include env specific configuration file
and put inside /path/to/pod.conf:
db {
password = "pod_db_pass"
}
So eventually contents of both files will be merged inside application during loading, and your final config will contain password at path db.password
UPDATE
Another possible option load password from file and merge into config file with withFallback method. Example:
import com.typesafe.config._
val passord = "password_from_file"
val passwordConfig = ConfigFactory.parseString(s"db.password=$passord")
val applicationConfig = ConfigFactory.parseString(s"db.user=db_user")// Replace this with `ConfigFactory.load()`
val config = applicationConfig.withFallback(passwordConfig)
println(config)
Printout result:
Config(SimpleConfigObject({"db":{"password":"password_from_file","user":"db_user"}}))
Scatie: https://scastie.scala-lang.org/WW3weuqiT9WRUKfdrZgwcw