Helm dependencies - Reference to values inside the helm dependancy (dependency outputs) - kubernetes

Question

I'll give the context first then the problem: I am interested in centralising a set of values that would be in my values.yaml.
Initial plan was to create a config map with the centralised values that I could load using the lookup helm function. Sadly for me the CD tool I use (ArgoCD) doesn't support lookup.
Current chain of thought would be to create a dummy helm chart that would contain the centralised values. I would set this helm chart as a dependency. Can I get some outputs out of this dependancy that can be used elsewhere? If yes, how to refer to them in the values.yaml?

Answer 1

One approach could be like this:
Create a folder structure such as this
yourappfolder
- Chart.yaml
- value.yaml // the main value file
- value.dev.yaml //contains env-specific values and override value.yaml
and publish a completely new helm chart like my-generic-chart to a registry with default values already placed and update it in Chart.yaml as a dependency
# Chart.yaml
apiVersion: v2
name: myapplication
description: A Helm chart for Kubernetes
type: application
version: 0.1.0
appVersion: "1.16.0"
dependencies:
- name: my-generic-chart
version: 5.6.0
repository: "URL to your my-default-chart"
and don't forget to put all the values under my-default-chart
# values.yaml
my-default-chart:
image: nginx
imageTag: 1
envs:
log-format: "json"
log-level: "none"
..
..
# values.dev.yaml
my-default-chart:
imageTag: 1.1
envs:
log-level: "debug"
..
..
the values.dev.yaml file will override the values in values.yaml and both of them together will override the values in the generic chart default values.yaml file.
Now you have to create a generic chart that fits to all of your applications or create a generic chart for each type of application

Answer 2

Figured it is possible by 2 ways:
Exporting/Importing child values: https://helm.sh/docs/topics/charts/#importing-child-values-via-dependencies and I found a great related answer: How to use parameters of one subchart in another subchart in Helm
Using "Templates": https://helm.sh/docs/chart_template_guide/subcharts_and_globals/#sharing-templates-with-subcharts "Parent charts and subcharts can share templates. Any defined block in any chart is available to other charts."
I create one chart "data" that doesn't create anything but creates template function (for example "data.project") then I use another
├── Chart.lock
├── Chart.yaml
├── charts
│   ├── data
│   │   ├── Chart.yaml
│   │   ├── templates
│   │   │   └── _helpers.tpl
│   │   └── values.yaml
│   ├── sub0
│   │   ├── Chart.yaml
│   │   ├── templates
│   │   │   └── configmap.yaml
│   │   └── values.yaml
└── values.yaml
charts/data/templates/_helpers.tpl contains:
{{- define "data.project" -}}
project_name
{{- end }}
The top Chart.yaml contains:
---
apiVersion: v2
name: multi
type: application
version: 0.1.0
appVersion: "1.16.0"
dependencies:
- name: data
version: 0.1.0
repository: "file://charts/data" # This is while testing locally, once shared in a central repository this will achieve the centralised data information
import-values:
- data
- name: sub0
version: 0.1.0
repository: "file://charts/sub0"
Then from anywhere I can do:
"{{ include \"data.project\" . }}"
And obtain the value
Of course the "data" chart will need to live in a separate repository