Consuming entries of a ConfigMap created from property files

Question

The example on the documentation (http://kubernetes.io/docs/user-guide/configmap/) for consuming values is based on a ConfigMap where each data entry is a single pair/value. Example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: charm

However when we create a ConfigMap from property files, every data entry value is itself a list of key/pair values. Example:

$ kubectl get configmaps game-config -o yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: game-config
  [...]
data:
  game.properties: |-
    enemies=aliens
    lives=3
    enemies.cheat=true
    enemies.cheat.level=noGoodRotten
    secret.code.passphrase=UUDDLRLRBABAS
    secret.code.allowed=true
    secret.code.lives=30
  [...]

In such a case:

1. How do we consume a single entry (example: enemies.cheat) as an environment variable?
2. How do we consume all the entries (example: all game.properties entries) as a set of environment variables, assuming we just use each key as the environment variable name?

Answer 1

You can't consume a single entry since it is just one big blob of text. You have two options that I see:

1. Don't create the config map from a file. Instead create each entry in the ConfigMap manually. You'll have to consume each key separately though, at least until this issue is resolved.

2. Don't use the ConfigMap as environment variables. Instead mount that key as a volume and have your application read the key/values.

It seems like the second option would work nicely for you. It would let you continue to generate your ConfigMap from a file, and also allow you to consume all declared key/values without having to constantly change your Kubernetes manifests.

Another advantage of mounting your ConfigMap as a volume is that it will allow you to perform in-place updates to your configs (assuming that your app tolerates that). If you mount ConfigMap keys as environment variables the only way to update them is to restart the app.