Kubernetes - ConfigMap for nested variables - kubernetes

Question

We have an image deployed in an AKS cluster for which we need to update a config entry during deployment using configmaps.
The configuration file has the following key and we are trying to replace the value of the "ChildKey" without replacing the entire file -
{
"ParentKey": {
"ChildKey": "123"
}
}
The configmap looks like -
apiVersion: v1
data:
ParentKey: |
ChildKey: 456
kind: ConfigMap
name: cf
And in the deployment, the configmap is used like this -
apiVersion: extensions/v1beta1
kind: Deployment
spec:
template:
metadata:
creationTimestamp: null
labels:
app: abc
spec:
containers:
- env:
- name: ParentKey
valueFrom:
configMapKeyRef:
key: ParentKey
name: cf
The replacement is not working with the setup above. Is there a different way to declare the key names for nested structures?

Answer 1

We have addressed this in the following manner -
The configmap carries a simpler structure - only the child element -
apiVersion: v1
data:
ChildKey: 456
kind: ConfigMap
name: cf
In the deployment, the environment variable key refers to the child key like this -
apiVersion: extensions/v1beta1
kind: Deployment
spec:
template:
metadata:
creationTimestamp: null
labels:
app: abc
spec:
containers:
- env:
- name: ParentKey__ChildKey
valueFrom:
configMapKeyRef:
key: ChildKey
name: cf
Posting this for reference.

Answer 2

use the double underscore for nested environment variables and arrays as explained here
To avoid explicit environment variables and typing names twice, you can use envFrom
configMap.yaml
apiVersion: v1
data:
ParentKey__ChildKey: 456
kind: ConfigMap
name: cf
deployment.yml
containers:
- name: $(name)
image: $(image)
envFrom:
- configMapRef:
name: common-config
- configMapRef:
name: specific-config