How to reference a value defined in a template in a sub-chart in helm for kubernetes?

Question

I\'m starting to write helm charts for our services.

There are two things I\'m not sure how they are supposed to work or what to do with them.

First: the rel

Answer 1

Are you pulling in postgresql as a subchart of your chart (via your chart's requirements.yaml)? If so, both the postgresql (sub) chart and your chart will have the same .Release.Name - thus, you could specify your container's environment as

  env:
    - name: DB_HOST
      value: {{ printf "%s-postgresql" .Release.Name }}

if you override postgresql's name by adding the following to your chart's values.yaml:

postgresql:
  nameOverride: your-postgresql

then your container's env would be:

  env:
    - name: DB_HOST
      value: {{ printf "%s-%s" .Release.Name .Values.postgresql.nameOverride }}

Answer 2

You can overwrite the values of the subchart with the values of the parent chart as described here: https://github.com/kubernetes/helm/blob/master/docs/chart_template_guide/subcharts_and_globals.md

I don't think it's possible (and it also doesn't make sense) to override the template name of the subchart.

What I would do is define the database service name in the .Values files both in the parent and sub charts and let helm override the one in the subchart - that way you will always have the database name in the parent chart. This would however mean that the service name of the database should not be {{ template "name" . }}, but something like {{ .Values.database.service.name }}

mychart/.Values

mysubchart:
   service:
      name: my-database

mychart/templates/deployment.yaml

env:
   - name: DB_HOST
     value: {{ .Values.mysubchart.service.name }}

mychart/charts/mysubchart/.Values

service:
   name: my-database

mychart/charts/mysubchart/templates/service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: {{ .Values.service.name }}

Another way is to use global chart values, also described in https://github.com/kubernetes/helm/blob/master/docs/chart_template_guide/subcharts_and_globals.md