helm check for required variables in a single file

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I'd like to have a file that checks for all "required" variables. So far I came up with this, but it doesn't look like this is "best" practices

values.yaml

# this is required name of the hosted zone
domainZone: "" 
someOtherRequireVar: ""

/templates/required.yaml

# the block below makes sure that our required variables are 
# declared in the values file and if not that will throw the error
# so even the block below is commeted, it's still evaluated by the HELM and error
# will be generated if the variable's value is not set
# {{ .Values.domainZone | required "Domain Zone is required and should be non-empty string" }}
# {{ .Values.someOtherRequireVar | required "The someOtherRequireVar is also required and should be non-empty string" }}

Are there better ways to achieve this?

helm3 kubernetes-helm
1 Answers

I'd recommend using named templates for validation, which you can execute in your installation notes instead of regular template files. Furthermore, by using failsafe validation functions (unlike require) for individual values, you can validate multiple values before failing execution of your helm command.

Bitnami charts use this strategy.

Setup

In a partials file, e.g. templates/_helpers.tpl, define named templates for validating the supplied values:

{{/* Compile all validation warnings into a single message and call fail. */}}
{{- define "mychart.validateValues" -}}
{{- $messages := list -}}
{{- $messages = append $messages (include "mychart.validateValues.foo" .) -}}
{{- $messages = append $messages (include "mychart.validateValues.bar" .) -}}
{{- $messages = without $messages "" -}}
{{- $message := join "\n" $messages -}}

{{- if $message -}}
{{- printf "\nVALUES VALIDATION:\n%s" $message | fail -}}
{{- end -}}
{{- end -}}

{{/* Validate value of foo */}}
{{- define "mychart.validateValues.foo" -}}
{{- if not (and .Values.foo (kindIs "string" .Values.foo)) -}}
mychart: foo
    `foo` is required and should be a non-empty string
{{- end -}}
{{- end -}}

{{/* Validate the value of bar */}}
{{- define "mychart.validateValues.bar" -}}
{{- if not (and .Values.bar (kindIs "string" .Values.bar)) -}}
mychart: bar
    `bar` is required and should be a non-empty string
{{- end -}}
{{- end -}}

In this case, the named template mychart.validateValues will run multiple validations (i.e. mychart.validateValues.foo, mychart.validateValues.bar). If one or more validations produce a validation warning, it will call fail with a summary of the warnings.

In templates/NOTES.txt, evaluate the named template for validation:

{{- include "mychart.validateValues" . }}

Test

With the following values.yaml file:

bar: 24

Templating, installing, or upgrading the chart will fail with the following message:

Error: execution error at (test/templates/NOTES.txt:1:4): 
VALUES VALIDATION:
mychart: foo
    `foo` is required and should be a non-empty string
mychart: bar
    `bar` is required and should be a non-empty string
user_50999710
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