error-pages/templates/readme.md

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# Templates
Creating templates is a very simple operation, even for those who know nothing at all about [Go Template](https://pkg.go.dev/text/template). All you should know is:
- The template should be one page. Without additional `css` or `js` files (but you can load them from the CDN or another GitHub repositories using [jsdelivr.com](https://www.jsdelivr.com/), for example)
- Don't forget to include `<meta name="robots" content="noindex, nofollow" />` tag in the header
- You can use a special "placeholders" (wrapped in `{{` and `}}`) for the rendering error code, message and others (see details below)
## Supported signatures
### Error page & request data
| Signature | Description | Example |
|--------------------------------------|---------------------------------------------------------------|----------------------------------------------|
| `{{ code }}` | Error page code | `404` |
| `{{ message }}` | Error code message | `Not found` |
| `{{ description }}` | Error code description | `The server can not find the requested page` |
| `{{ original_uri }}` | `X-Original-URI` header value | `/foo1/bar2` |
| `{{ namespace }}` | `X-Namespace` header value | `foo` |
| `{{ ingress_name }}` | `X-Ingress-Name` header value | `bar` |
| `{{ service_name }}` | `X-Service-Name` header value | `baz` |
| `{{ service_port }}` | `X-Service-Port` header value | `8080` |
| `{{ request_id }}` | `X-Request-ID` header value | `12AB34CD56EF78` |
| `{{ forwarded_for }}` | `X-Forwarded-For` header value | `203.0.113.195, 70.41.3.18` |
| `{{ host }}` | `Host` header value | `example.com` |
| `{{ now.Unix }}` | Current timestamp (e.g. in Unix format) | `1643621927` |
| `{{ hostname }}` | OS hostname | `ab12cd34ef56` |
| `{{ version }}` | Application version | `2.5.0` |
| `{{ if show_details }}...{{ end }}` | Logical operator (server started with "show details" option?) | |
| `{{ if hide_details }}...{{ end }}` | Same as above, but inverted | |
| `{{ if l10n_enabled }}...{{ end }}` | Logical operator (l10n is enabled?) | |
| `{{ if l10n_disabled }}...{{ end }}` | Same as above, but inverted | |
### Modifiers
| Signature | Description | Example |
|------------------------------------|--------------------------------|-------------------------------------|
| <code>{{ ... &#124; json }}</code> | Convert value into json-string | <code>{{ code &#124; json }}</code> |
| <code>{{ ... &#124; int }}</code> | Convert value into integer | <code>{{ code &#124; int }}</code> |