Extend configMapGenerator to work with application.yml files

[mcdolding]

The configMapGenerator will manage a configmap using properties of the form myproperty=myvalue.
However I have springboot and quarkus applications which are configured using application.yml files (in place of application.properties files). At runtime we provide configmaps of the form:

  - kind: ConfigMap
    apiVersion: v1
    data:
      application.yml: |-
        my:
	  nested:
	    property1: myvalue1
	    property2: myvalue2

Would it be possible to extend configMapGenerator to handle yml properties?

[stormqueen1990]

Hello there, @mcdolding! 👋🏻

Currently, it's possible to add YAML file contents to a Kustomization using the configMapGenerator through the files field, or the --from-file CLI option if you're using kustomize edit add. For example, in a directory structure such as:

.
|____kustomization.yaml
|____application.yaml

where your application.yaml has a content such as:

server:
  port: 8080

you could use kustomize edit add configmap test-cm --namespace test-ns --from-file=application.yaml to generate the following kustomization.yaml:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
configMapGenerator:
- files:
  - application.yaml
  name: test-cm
  namespace: test-ns

which would then generate the following structure on kustomize build:

apiVersion: v1
data:
  application.yaml: |
    server:
      port: 8080
kind: ConfigMap
metadata:
  name: test-cm-bd9fg9hb5h
  namespace: test-ns

It's also possible to override the YAML key when using --from-file by specifying it before the file name. For instance, running kustomize edit add configmap test-cm --namespace test-ns --from-file=test.yaml=application.yaml would yield:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
configMapGenerator:
- files:
  - test.yaml=application.yaml
  name: test-cm
  namespace: test-ns

which then results in:

apiVersion: v1
data:
  test.yaml: |
    server:
      port: 8080
kind: ConfigMap
metadata:
  name: test-cm-d76c2hh757
  namespace: test-ns

Does that address your use case?

[mcdolding]

Thanks for your detailed response. This is exactly what I need.

[jonenst]

Hi @stormqueen1990 , do you know if there is an easy way to write application.yaml files like this

a:
  b:
    c: val1
    d: val2

and from them generate configmaps like this:

data:
  a.b.c: val1
  a.b.d: val2

My use case is to be able to compose/override values in these application.yaml files. If you have everything in one big file, you can't selectively add/override values. Instead, if you have everything as one key in the configmap, you can mount this as a configtree and spring knows how to read them in the same way as one big file. And so you can use behavior: merge or behavior: replace to compose configmaps.

One alternative is to mount many big application.yaml files and rely on spring's order of precedence (usually with a wildcard like /config/* you get alphabetical order precedence) but I always find this not practical because each application.yaml needs to be in its own folder.
Another possibility is to have one big folder with many application-XXX.yaml files where XXX is the profile, but then you have to separately activate these profiles and I don't think there's a composable way to do this.
A third alternative is to define the values manually like for properties, but it's pretty verbose espacially if you have deeply nested configuration (you need to repeat the prefix at each line). And it doesn't look like the usual spring yaml format (it looks more lire the usual spring properties format). Or you could define environment variables in the same way

Spring documentation on its configuration: https://docs.spring.io/spring-boot/reference/features/external-config.html

Maybe you have more insight on this topic ?

TIA,
Jon