b8722ce83b
This is actually several refactors in one: * rename "fileContent" function to "insertFile" * pass the resource set path to the "insetFile" function * update docs and example with a pipeline including indentation adjustments for the inserted file
147 lines
3.7 KiB
Markdown
147 lines
3.7 KiB
Markdown
Kontemplate templates
|
|
=====================
|
|
|
|
The template file format is based on Go's [templating engine][] in combination
|
|
with a small extension library called [sprig][] that adds additional template
|
|
functions.
|
|
|
|
Go templates can either simply display variables or build more complicated
|
|
*pipelines* in which variables are passed to functions for further processing,
|
|
or in which conditionals are evaluated for more complex template logic.
|
|
|
|
It is recommended that you check out the Golang [documentation][] for the templating
|
|
engine in addition to the cherry-picked features listed here.
|
|
|
|
<!-- markdown-toc start - Don't edit this section. Run M-x markdown-toc-refresh-toc -->
|
|
**Table of Contents**
|
|
|
|
- [Kontemplate templates](#kontemplate-templates)
|
|
- [Basic variable interpolation](#basic-variable-interpolation)
|
|
- [Example:](#example)
|
|
- [Template functions](#template-functions)
|
|
- [Examples:](#examples)
|
|
- [Conditionals & ranges](#conditionals--ranges)
|
|
- [Caveats](#caveats)
|
|
|
|
<!-- markdown-toc end -->
|
|
|
|
## Basic variable interpolation
|
|
|
|
The basic template format uses `{{ .variableName }}` as the interpolation format.
|
|
|
|
### Example:
|
|
|
|
Assuming that you include a resource set as such:
|
|
|
|
```
|
|
- name: api-gateway
|
|
values:
|
|
internalHost: http://my-internal-host/
|
|
```
|
|
|
|
And the api-gateway resource set includes a ConfigMap (some fields left out for
|
|
the example):
|
|
|
|
```
|
|
# api-gateway/configmap.yaml:
|
|
---
|
|
kind: ConfigMap
|
|
metadata:
|
|
name: api-gateway-config
|
|
data:
|
|
internalHost: {{ .internalHost }}
|
|
```
|
|
|
|
The resulting output will be:
|
|
|
|
```
|
|
|
|
---
|
|
kind: ConfigMap
|
|
metadata:
|
|
name: api-gateway-config
|
|
data:
|
|
internalHost: http://my-internal-host/
|
|
```
|
|
|
|
## Template functions
|
|
|
|
Go templates support template functions which you can think of as a sort of
|
|
shell-like pipeline where text flows through transformations from left to
|
|
right.
|
|
|
|
Some template functions come from Go's standard library and are listed in the
|
|
[Go documentation][]. In addition the functions declared by [sprig][] are
|
|
available in kontemplate, as well as three custom functions:
|
|
|
|
* `json`: Encodes any supplied data structure as JSON.
|
|
* `passLookup`: Looks up the supplied key in [pass][].
|
|
* `insertFile`: Insert the contents of the given file in the resource
|
|
set folder as a string.
|
|
|
|
## Examples:
|
|
|
|
```
|
|
# With the following values:
|
|
name: Donald
|
|
certKeyPath: my-website/cert-key
|
|
|
|
# The following interpolations are possible:
|
|
|
|
{{ .name | upper }}
|
|
-> DONALD
|
|
|
|
{{ .name | upper | repeat 2 }}
|
|
-> DONALD DONALD
|
|
|
|
{{ .certKeyPath | passLookup }}
|
|
-> Returns content of 'my-website/cert-key' from pass
|
|
```
|
|
|
|
## Conditionals & ranges
|
|
|
|
Some logic is supported in Golang templates and can be used in Kontemplate, too.
|
|
|
|
With the following values:
|
|
|
|
```
|
|
useKube2IAM: true
|
|
servicePorts:
|
|
- 8080
|
|
- 9090
|
|
```
|
|
|
|
The following interpolations are possible:
|
|
|
|
```
|
|
# Conditionally insert something in the template:
|
|
metadata:
|
|
annotations:
|
|
foo: bar
|
|
{{ if .useKube2IAM -}} iam.amazonaws.com/role: my-api {{- end }}
|
|
```
|
|
|
|
```
|
|
# Iterate over a list of values
|
|
ports:
|
|
{{ range .servicePorts }}
|
|
- port: {{ . }}
|
|
{{ end }}
|
|
```
|
|
|
|
Check out the Golang documentation (linked above) for more information about template logic.
|
|
|
|
## Caveats
|
|
|
|
Kontemplate does not by itself parse any of the content of the templates, which
|
|
means that it does not validate whether the resources you supply are valid YAML
|
|
or JSON.
|
|
|
|
You can perform some validation by using `kontemplate apply --dry-run` which
|
|
will make use of the Dry-Run functionality in `kubectl`.
|
|
|
|
[templating engine]: https://golang.org/pkg/text/template/
|
|
[documentation]: https://golang.org/pkg/text/template/
|
|
[sprig]: http://masterminds.github.io/sprig/
|
|
[Go documentation]: https://golang.org/pkg/text/template/#hdr-Functions
|
|
[pass]: https://www.passwordstore.org/
|