Here is an example of helm helper intended for getting values from custom file

How it works

• In the repo we have merge_values helm chart with the following file structure

tree merge_values

↳ output:

merge_values
├── Chart.yaml
├── charts
├── templates
│   ├── _helpers.tpl
│   └── configmap.yaml
├── values-develop.yaml
└── values.yaml

3 directories, 5 files

• In the chart we have
  • templates/_helpers.tpl - file with helm helpers, it particulary defines the named template read_values_from_file
  • templates/configmap.yaml - exemplary helm template file for ConfigMap kubernetes object, which uses the above named template
  • values.yaml - file with default values
  • values-develop.yaml - file with values for custom develop environment
• When we install the helm chart we can pass to helm install command (e.g. with --set flag) the value for env variable corresponding to the custom environment (develop in our case)
• Then we can use named template read_values_from_file (defined within templates/_helpers.tpl file) in any of our helm templates to have access to values defined in the custom environment file (custom environment is set with the passed env variable to the helm install command)
• The values from values-develop.yaml and values.yaml files will be merged and available to use throughout the helm template
• Named template read_values_from_file is defined within templates/_helpers.tpl file

{{- define "read_values_from_file" }}
{{- $filename := cat "values-" .Values.env ".yaml" | nospace }}
{{- $dict := . }}
{{- $_ := set $dict "envValues" (dict) }}
{{- range $path, $_ := .Files.Glob $filename }}
{{- $envValues := $.Files.Get $path | fromYaml }}
{{- $_ := set $dict "envValues" $envValues }}
{{- end }}
{{- end }}

• To use it the following structures is necessary

{{- $d := dict "Values" .Values "Files" .Files }}
{{- include "read_values_from_file" $d }}
{{- $v := merge $d.envValues $d.Values }}

• $d dictionary is passed to the named template as current context (to have access to .Values.env and .Files.Glob) and used to return values read from file corresponding to the custom environment
• $v will contain all the default Values merged with values defined for custom environment (if corresonding file for the custom environment exists), with custom environment values having precedence

How to use

• Clone the repo and change to the repo directory

git clone https://github.com/cloud-simple/helm-values-from-file.git && cd helm-values-from-file

• Run the following command setting the environment variable env (with flag --set env=develop) and see how default values (from merge_values/values.yaml file) are merged with values from the file corresponding to the environment (merge_values/values-develop.yaml)

helm install --set env=develop --debug --dry-run test-merge ./merge_values

↳ output:

install.go:200: [debug] Original chart version: ""
install.go:217: [debug] CHART PATH: /Users/.../helm-values-from-file/merge_values

NAME: test-merge
LAST DEPLOYED: Tue Jun 27 14:55:34 2023
NAMESPACE: default
STATUS: pending-install
REVISION: 1
TEST SUITE: None
USER-SUPPLIED VALUES:
env: develop

COMPUTED VALUES:
env: develop
meta:
  env: This is default value for Metadata Environment variable
replicas: 1
some: not_to_override

HOOKS:
MANIFEST:
---
# Source: merge_values/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-merge
data:
  env: develop
  filename: values-develop.yaml
  merged-values: |
    map[env:dev-NOT-develop meta:map[description:When we have a special vaiable, let's say 'env', which define the deployment environment, we would like to look for a file with values corresponding to that environment and read values from it env:This is a value for Metadata Environment variable from custom file idea:To be able to read values from custom file (e.g. indentified with help of 'env' variable passed with --set flag) and merge them with other values] replicas:2 some:not_to_override]

• Run the following command without setting the environment variable env and see how default values are used

Note

The default value for env variable is main (as defined in merge_values/values.yaml file), and custom values file corresponding to the main environment is values-main.yaml, which doesn't exist, but this situation is processed correctly

helm install --debug --dry-run test-merge ./merge_values

↳ output:

install.go:200: [debug] Original chart version: ""
install.go:217: [debug] CHART PATH: /Users/.../Helm/helm-values-from-file/merge_values

NAME: test-merge
LAST DEPLOYED: Tue Jun 27 15:21:17 2023
NAMESPACE: default
STATUS: pending-install
REVISION: 1
TEST SUITE: None
USER-SUPPLIED VALUES:
{}

COMPUTED VALUES:
env: main
meta:
  env: This is default value for Metadata Environment variable
replicas: 1
some: not_to_override

HOOKS:
MANIFEST:
---
# Source: merge_values/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-merge
data:
  env: main
  filename: values-main.yaml
  merged-values: |
    map[env:main meta:map[env:This is default value for Metadata Environment variable] replicas:1 some:not_to_override]