externalref

External Reference Example

Reads existing cluster resources with externalRef: one ConfigMap by name for platform configuration, and a set of ConfigMaps by label selector whose data is aggregated into status with CEL list functions. See the External Reference Example in the top-level README for the full walkthrough on a live cluster.

Render it locally

External references resolve from real cluster resources, which crossplane render mocks with --required-resources. The example includes the same ConfigMaps (configmap.yaml, subscribers.yaml) it applies on a cluster.

Start function-kro from the repository root:

go run . --insecure --debug

Render the example, passing the external ConfigMaps:

cd example/externalref
crossplane render -r -x xr.yaml composition.yaml functions.yaml \
  --required-schemas=schemas/ \
  --required-resources=configmap.yaml \
  --required-resources=subscribers.yaml

Because the ConfigMaps are supplied, the status aggregates fully: platformConfig carries the region, environment, and CIDR from the single ConfigMap, and notifications reports subscriberCount, the sorted teams, and hasOncall computed across all subscriber ConfigMaps. The VPC renders with configuration sourced from the ConfigMap; the subnet and security group depend on the VPC's ID and reconcile on a cluster.

To reference cluster-scoped resources, use label-selector. If metadata.name is set, kro will default to the instance namespace.