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