This guide covers some of the tips and tricks Helm chart developers have learned while building production-quality charts.
When you are working with string data, you are always safer quoting the strings than leaving them as bare words:
name: {{.Values.MyName | quote }}
But when working with integers do not quote the values. That can, in many cases, cause parsing errors inside of Kubernetes.
port: {{ .Values.Port }}
Go provides a way of including one template in another using a built-in
template directive. However, the built-in function cannot be used in
Go template pipelines.
To make it possible to include a template, and then perform an operation
on that template's output, Helm has a special include function:
{{ include "toYaml" $value | indent 2 }}
The above includes a template called toYaml, passes it $value, and
then passes the output of that template to the indent function.
Because YAML ascribes significance to indentation levels and whitespace, this is one great way to include snippets of code, but handle indentation in a relevant context.
Sometimes you want to create some reusable parts in your chart, whether they're blocks or template partials. And often, it's cleaner to keep these in their own files.
In the templates/ directory, any file that begins with an
underscore(_) is not expected to ouput a Kubernetes manifest file. So
by convention, helper templates and partials are placed in a
_helpers.tpl file.
According to the YAML specification, YAML is a superset of JSON. That means that any valid JSON structure ought to be valid in YAML.
This has an advantage: Sometimes template developers may find it easier to express a datastructure with a JSON-like syntax rather than deal with YAML's whitespace sensitivity.
As a best practice, templates should follow a YAML-like syntax unless the JSON syntax substantially reduces the risk of a formatting issue.
There are functions in Helm that allow you to generate random data, cryptographic keys, and so on. These are fine to use. But be aware that during upgrades, templates are re-executed. When a template run generates data that differs from the last run, that will trigger an update of that resource.