helm chart - value file variables

Question

I am using a helm chart (with sub-charts) to deploy my application. I am using a value file for setting values.

I am looking a way to set variables in my value file (or any other place) that will be valid for my value file.

I have some sections (services) in my value files that I need to use the same value in it so I am looking for a variable in my value file. Is there any way that I can use variables for my value file? Thx

Answer 1

Helm on its own can't do this.

If you control all of the charts and subcharts, you can allow specific values to have embedded Go templating. Helm includes a tpl extension function that will let you render an arbitrary string as a template. So if you have values

global:
  commonKey: some value
otherKey: '{{ .Values.global.commonKey }}'

then you can render

- name: OTHER_KEY
  value: '{{ tpl .Values.otherKey . }}'

But, you have to use tpl every place you access the key value(s); if you don't control the subcharts you may not be able to do this.

Higher-level tools may also let you do this. I'm familiar in particular with Helmfile which lets you declare multiple Helm charts and their settings, but also lets you use almost-Helm templating in many places. So your helmfile.yaml could specify:

environments:
  default:
    # These values are available when rendering templates in this file
    values:
      - commonKey: some value
releases:
  - name: my-service
    namespace: my-service
    chart: ./charts/my-service
    values:
      # List items can be file names or YAML dictionaries.
      # If it's a dictionary, arbitrary nested values.yaml content.
      # If it's a *.yaml.gotmpl file name, templating is applied to the file.
      - otherKey: '{{ .Values.commonKey }}'
        yetAnotherKey: '{{ .Values.commonKey }}'
      - ./my-service.yaml.gotmpl

Helmsman is simpler, but can only set chart values from environment variables; but I believe you can reference the same environment variable in different setString: options. You could also do something similar with the Terraform Helm provider, using Terraform's native expression syntax, particularly if you're already familiar with Terraform.