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Controller Implementation Overrides

Config Connector allows you to explicitly choose which underlying controller implementation (Direct, Terraform, or DCL) to use for a specific resource kind. This is primarily used when transitioning resources from legacy implementations to newer "Direct" controllers.

Controller Types

Config Connector uses different underlying implementations (controller types) to manage Google Cloud resources:

  • Direct Controllers: Newer implementations that call Google Cloud APIs directly using controller-runtime. These are preferred for simplicity and performance.
  • Terraform-based Controllers (TF): Older implementations that wrap the Terraform Google provider.
  • DCL-based Controllers: Older implementations that wrap the Google Cloud Declarative Library (DCL).

Overriding the Controller Type

You can override the default implementation for a specific resource kind within a namespace using the experiments.controllerOverrides field in ConfigConnectorContext.

Note: You can only override to a controller type that is explicitly supported for that resource. See Finding Supported Controller Types.

Example

The following ConfigConnectorContext configures Config Connector to use the direct controller for BigQueryDataset resources in the my-namespace namespace:

apiVersion: core.cnrm.cloud.google.com/v1beta1
kind: ConfigConnectorContext
metadata:
  name: configconnectorcontext.core.cnrm.cloud.google.com
  namespace: my-namespace
spec:
  googleServiceAccount: "kcc-sa@my-project.iam.gserviceaccount.com"
  experiments:
    controllerOverrides:
      BigQueryDataset.bigquery.cnrm.cloud.google.com: direct

Precedence

Config Connector determines which controller type to use following this order of precedence:

  1. Legacy Resource Annotation (deprecated): The alpha.cnrm.cloud.google.com/reconciler or cnrm.cloud.google.com/reconciler annotation on the individual resource.
  2. ConfigConnectorContext Override: The experiments.controllerOverrides entry in the namespace's ConfigConnectorContext.
  3. Static Default: The default implementation defined in the Config Connector version.

For more information on legacy behaviors and annotations, see Legacy Behavior.

Verifying the Controller Type

To determine which controller type is being used for a resource:

  1. Check Overrides: Inspect the ConfigConnectorContext in the resource's namespace.
  2. Check Static Config: Consult the static_config.go file in the repository.
  3. Inspect Logs: View the logs of the cnrm-controller-manager pod.

Finding Supported Controller Types

Consult the static_config.go file in the repository. For each resource kind, the file defines:

  • DefaultController: The controller type used if no override is specified.
  • SupportedControllers: The list of types that can be used as an override.

Example entry:

{Group: "bigquery.cnrm.cloud.google.com", Kind: "BigQueryDataset"}: {
    DefaultController: k8s.ReconcilerTypeTerraform, 
    SupportedControllers: []k8s.ReconcilerType{k8s.ReconcilerTypeDirect, k8s.ReconcilerTypeTerraform}
},

Inspecting Logs

Look for the "routing to controller" message in the cnrm-controller-manager logs (requires V(1) verbosity).

kubectl -n cnrm-system logs pod/cnrm-controller-manager-0 | grep "routing to controller"

Example Log Output: Info routing to controller {"resource": {"namespace": "my-namespace", "name": "my-resource"}, "type": "direct"}

Further Reading