Client and Scheme

The Object Reconciler talks to the target cluster through a cluster.Client. This page describes what that client must provide, and what its scheme must recognize.

The cluster.Client interface

package cluster

// The Client interface extends the controller-runtime client by discovery and
// event recording capabilities.
type Client interface {
	client.Client
	// Return a discovery client.
	DiscoveryClient() discovery.DiscoveryInterface
	// Return an event recorder.
	EventRecorder() record.EventRecorder
	// Return a rest config for this client.
	Config() *rest.Config
	// Return a http client for this client.
	HttpClient() *http.Client
}

In other words, a cluster.Client is a controller-runtime client.Client augmented with a few extras the reconciler relies on:

• the embedded client.Client for the usual CRUD operations, and — through it — a RESTMapper() and a Scheme();
• a discovery client, used to resolve served resources;
• an event recorder, used to emit events on dependent objects (created / updated / deleted), unless events are disabled via ReconcilerOptions.EnableEvents or per object annotation mycomponent-operator.mydomain.io/disable-events;
• a REST config and HTTP client for lower-level access.

Scheme requirements

The scheme of the passed client must recognize at least:

• the core group (v1),
• apiextensions.k8s.io/v1 (for CustomResourceDefinition), and
• apiregistration.k8s.io/v1 (for APIService).

These are required because the reconciler inspects and specially handles namespaces, secrets, CRDs and APIServices. Beyond that, the scheme should recognize the concrete types of the objects you apply if you pass typed (non-Unstructured) manifests; unstructured objects with valid type information are also accepted and are converted to their concrete type when known to the scheme.

See also

• Overview — where the client is passed to NewReconciler.