CODEWITHSUNDEEP
kuberneteskubernetes-helmgo-templates
QuirkyBit
QuirkyBit

Reputation: 772

Replaces command for label in helm charts

I often see the following snippet in the helm charts:

  labels:
    app: {{ template "app.name" . }}
    chart: {{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}

Why is the replacement necessary? Are + signs bad?

Upvotes: 3

Views: 4724

Answers (2)

Malgorzata
Malgorzata

Reputation: 7023

Replace - script and chart function Replace() returns a string after replacing all occurrences of a given substring within the input string with another substring. The function is non-recursive and works from left to right.

Syntax:

Replace(text, from_str, to_str) Return data type: string

Valid label values in pod configuration file must be 63 characters or less and must be empty or begin and end with an alphanumeric character ([a-z0-9A-Z]) with dashes (-), underscores (_), dots (.), and alphanumerics between.

replace "+" "_" replaces plus characters with underscores. And that is how we avoid failures.

More information you can find here: replace-chart, syntax-pod-label.

Upvotes: 2

Anmol Agrawal
Anmol Agrawal

Reputation: 904

As per this (https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#syntax-and-character-set) documentation, labels cannot have plus(+) character in its value. 

The name segment is required and must be 63 characters or less, beginning and ending with an alphanumeric character ([a-z0-9A-Z]) with dashes (-), underscores (_), dots (.), and alphanumerics between.

Upvotes: 4

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