Adding delegating reader for get and list requests for unstructured objs

* By default the client should not create informers for get and list
requsts of unstructured types.

Author: Shawn Hurley

pkg/client/split.go

@@ -16,6 +16,13 @@ limitations under the License.
 
 package client
 
+import (
+	"context"
+
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
 // DelegatingClient forms an interface Client by composing separate
 // reader, writer and statusclient interfaces.  This way, you can have an Client that
 // reads from a cache and writes to the API server.
@@ -24,3 +31,29 @@ type DelegatingClient struct {
 	Writer
 	StatusClient
 }
+
+// DelegatingReader forms a interface Reader that will cause Get and List
+// requests for unstructured types to use the ClientReader while
+// requests for any other type of object with use the CacheReader.
+type DelegatingReader struct {
+	CacheReader  Reader
+	ClientReader Reader
+}
+
+// Get retrieves an obj for a given object key from the Kubernetes Cluster.
+func (d *DelegatingReader) Get(ctx context.Context, key ObjectKey, obj runtime.Object) error {
+	_, isUnstructured := obj.(*unstructured.Unstructured)
+	if isUnstructured {
+		return d.ClientReader.Get(ctx, key, obj)
+	}
+	return d.CacheReader.Get(ctx, key, obj)
+}
+
+// List retrieves list of objects for a given namespace and list options.
+func (d *DelegatingReader) List(ctx context.Context, opts *ListOptions, list runtime.Object) error {
+	_, isUnstructured := list.(*unstructured.UnstructuredList)
+	if isUnstructured {
+		return d.ClientReader.List(ctx, opts, list)
+	}
+	return d.CacheReader.List(ctx, opts, list)
+}

pkg/manager/manager.go

@@ -138,12 +138,19 @@ func New(config *rest.Config, options Options) (Manager, error) {
 	}
 
 	return &controllerManager{
-		config:           config,
-		scheme:           options.Scheme,
-		errChan:          make(chan error),
-		cache:            cache,
-		fieldIndexes:     cache,
-		client:           client.DelegatingClient{Reader: cache, Writer: writeObj, StatusClient: writeObj},
+		config:       config,
+		scheme:       options.Scheme,
+		errChan:      make(chan error),
+		cache:        cache,
+		fieldIndexes: cache,
+		client: client.DelegatingClient{
+			Reader: &client.DelegatingReader{
+				CacheReader:  cache,
+				ClientReader: writeObj,
+			},
+			Writer:       writeObj,
+			StatusClient: writeObj,
+		},
 		recorderProvider: recorderProvider,
 	}, nil
 }