# Config

The domains defined here can be customized by the system administrator. By default, they’re loaded from `../../group_vars/all/04_applications.yml`, but you can override them per application in your repository:

```yaml
applications:
  {{ application_id }}:
    variable_a: "test string"  # Replaces the default value
    variable_b: {}             # Merges with the existing content
    variable_c: []             # Replaces the default value (use caution with domains)
```

## Placeholder Logic with `<< >>`

You can reference values from the generated `defaults_applications` dictionary at build time by embedding `<< ... >>` placeholders inside your template. For example:

```yaml
url: "{{ WEB_PROTOCOL }}://<< defaults_applications.web-svc-file.domains.canonical[0] >>/assets"
```

- The `<< ... >>` placeholders are resolved by the [`DictRenderer`](../../../utils/dict_renderer.py) helper class.
- The CLI uses the [`DefaultsGenerator`](../../../cli/build/defaults/applications.py) class to merge all role configurations into a single YAML and then calls the renderer to substitute each `<< ... >>` occurrence.
- Use the `--verbose` flag on the CLI script to log every replacement step, and rely on the built‑in timeout (default: 10 seconds) to prevent infinite loops.
