Kubernetes validation

Check values against the rules the API server applies to names and metadata: label keys and values, annotation keys, and DNS-1123 subdomains, so a bad value is caught with a clear message before the API server rejects it.

Reference

Functions

isDNS1123Subdomain

isDNS1123Subdomain reports whether a string is a syntactically valid DNS-1123 subdomain: lowercase alphanumeric segments (may contain -) separated by ., max 253 characters. This is the format Kubernetes requires for object names in most resource types, and for the prefix portion of a label/annotation key.

{{ isDNS1123Subdomain "api.example.com" }}  → true
{{ isDNS1123Subdomain "API_Example" }}      → false

isValidAnnotationKey

isValidAnnotationKey reports whether a string is a syntactically valid Kubernetes annotation key — the same [prefix/]name format as a label key. Annotation values have no Kubernetes format restriction of their own (that’s what distinguishes them from labels), so there is no isValidAnnotationValue function.

{{ isValidAnnotationKey "example.com/owner" }}  → true

isValidLabelKey

isValidLabelKey reports whether a string is a syntactically valid Kubernetes label key: [prefix/]name — name is alphanumeric (max 63 chars, may contain -, _, .), and prefix, if present, must be a valid DNS subdomain (max 253 chars).

{{ isValidLabelKey "app.kubernetes.io/name" }}  → true

isValidLabelValue

isValidLabelValue reports whether a string is a syntactically valid Kubernetes label value: max 63 characters, alphanumeric, may contain -, _, ., and must start and end with an alphanumeric character. An empty string is valid — Kubernetes treats an absent label value as permitted.

{{ isValidLabelValue "team-payments" }}  → true
{{ isValidLabelValue "team payments" }}  → false