Helm – Templating variables in values.yaml

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I’ll refer to the question’s title regarding templating variables in helm and suggest another option to use on values.yaml which is YAML Anchors.

Docs reference

As written in here:

The YAML spec provides a way to store a reference to a value, and
later refer to that value by reference. YAML refers to this as
“anchoring”:

coffee: "yes, please"
favorite: &favoriteCoffee "Cappucino"
coffees:
  - Latte
  - *favoriteCoffee
  - Espresso

In the above, &favoriteCoffee sets a reference to Cappuccino.

Later, that reference is used as *favoriteCoffee.
So coffees becomes Latte, Cappuccino, Espresso.

A more practical example

Referring to a common image setup (Registry and PullPolicy) in all values.yaml.

Notice how the default values are being set at Global.Image next to the reference definition which starts with &:

Global:
  Image:
    Registry: &global-docker-registry "12345678910.dkr.ecr.us-west-2.amazonaws.com" # <--- Default value
    PullPolicy: &global-pull-policy "IfNotPresent" # <--- Default value

Nginx:
  Image:
    Registry: *global-docker-registry
    PullPolicy: *global-pull-policy
    Version: 1.21.4
    Port: 80

MySql:
  Image:
    Registry: *global-docker-registry
    PullPolicy: *global-pull-policy
    Name: mysql
    Version: 8.0.27
    Port: 3306

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