`engine_provided_environment`

Some configurations are only known by the pipeline engine when instantiating a pipeline, which presents a problem when configuring a Transformer generically. Any transformer can optionally specify one of several environment variables that will be dynamically set by the pipeline engine. These are as follows:

KEYCLOAK_REALM_URL: URL to the Keycloak realm, of the form http(s)://<keycloak base url>/realms/<realm>. Read from the backend container’s environment.
KEYCLOAK_URL: The base URL of Keycloak, of the form http(s)://<keycloak base url>. Read from the backend container’s environment.
KEYCLOAK_REALM: The realm used by SDL services. Read from the backend container’s environment.
KEYCLOAK_CERTS_URI: URL to the platform’s Keycloak openid-connect/certs route.
HOSTNAME: The hostname of the Transformer as it is instantiated by the pipeline engine.

Example

"engine_provided_environment": [
    "HOSTNAME",
    "KEYCLOAK_REALM"
]

In the example above, when this Transformer is instantiated as part of a Pipeline, the Pipeline Engine will dynamically set the HOSTNAME and KEYCLOAK_REALM environment variables, which only it knows.