Scala component configuration

Our Scala components are in the process of switching from our own WhiskConfig to the TypesafeConfig based pureconfig. That will give us a more sane way of parsing environment values, overriding them and defining sensible defaults for them.

TypesafeConfig is able to override its values via JVM system properties. Unfortunately, docker only supports passing environment variables in a comfortable way.

To solve that mismatch, we use a script to transform environment variables into JVM system properties to spare the developer of manually overriding all the values via explicit environment -> TypesafeConfig value mapping. That script applies the following transformations to all environment variables starting with a defined prefix (“CONFIG_” in our case):

  • _ becomes . (TypesafeConfig hierarchies are built using .)
  • camelCased becomes camel-cased (Kebabcase is usually used for TypesafeConfig keys)
  • PascalCased stays PascalCased (Defining classnames for overriding SPIs is crucial)


  • CONFIG_whisk_loadbalancer_invokerBusyThreshold becomes -Dwhisk.loadbalancer.invoker-busy-threshold
  • CONFIG_akka_remote_netty_tcp_bindPort becomes -Dakka.remote.netty.tcp.bind-port
  • CONFIG_whisk_spi_LogStoreProvider becomes -Dwhisk.spi.LogStoreProvider