Helm Named Templates

External

• https://helm.sh/docs/chart_template_guide/named_templates/

Internal

• Helm Templates

Overview

A named template, also known as a partial, sub-template or embedded template, is a fragment of text that is declared in one file and then rendered in-line into another template, usually defined in a different file, every time it is invoked with the template action or the include function. A sub-template is declared with the define action. A sub-template name has a name, declared when the sub-template is defined. The sub-template body may contain action and function declaration, which will be rendered when the enclosing template is rendered.

Sub-Template Elements

Sub-Template Name

Sub-template names, including those declared in subcharts, are global. This means that if two sub-templates have the same name, whichever is loaded last will be the one to be used. For this reason, is a good practice to name the sub-templates with chart-specific names, and prefix the name of the sub-template with the name of the chart:

{{ define "mychart.mysubtemplate" }}

Using the chart name as a prefix, chart-specific sub-templates get their own namespace and that decreases the probability of conflict that may arise due to two different charts that implement templates with the same name.

Sub-Template Files

Sub-templates can be declared inside other template files, in helper files, for example _helpers.tpl, inside the chart's templates/ directory. _helpers.tpl is the default location for small sub-templates. If a sub-template is large enough, it can be stored in its own '_'-prefixed file. For more details on templates/ directory and template file conventions, see:

templates/

Actions

define

https://helm.sh/docs/chart_template_guide/named_templates/#declaring-and-using-templates-with-define-and-template

The 'define' action is used to declare the name and the content of the sub-template:

{{- define "mychart.mysubtemplate" }}
labels:
  color: blue
  date: {{ now | htmlDate }}
{{- end }}

Note that the indentation of the sub-template body is important. The template action will render as it, while the include function's output can be filtered and re-indented.

template

The 'template' action renders the specified sub-template, with the given scope, in the enclosing template.

...
kind: ConfigMap
metadata:
  name: test-cm
  {{- template "mychart.mysubtemplate" . }}
...

Note that "template" renders the sub-template body as is, reflecting the original indentation. The action output cannot be changed, and that is why the input function is almost always a better option to embed a sub-template.

TODEPLETE

tmp