Variable Interpolation

The orchestrator supports dynamic variable interpolation across all configuration files handled during the Templates and Config Injection phases.

This allows you to keep sensitive credentials or dynamic values (like hostnames, ports, or API keys) out of your template files and manage them entirely via Docker environment variables.

Usage

During the preparation phase, the orchestrator automatically scans for environment variable placeholders formatted as $[VARIABLE_NAME] in your payload files. These placeholders are directly interpolated and replaced with their actual runtime environment variable values.

Basic Example

If you have an environment variable DB_PASSWORD=secret123 and a template file config.yml:

database:
  password: $[DB_PASSWORD]

The resulting file in the runtime directory will be:

database:
  password: secret123

How it works

1. Detection: Before any merging or sigil processing occurs, the orchestrator reads the content of the payload file.
2. Replacement: Every instance of the $[...] pattern is replaced with the corresponding environment variable value.
3. Pipeline: The "interpolated" content is then passed down to the Deep Merging and Sigil processing engines.