Merge pull request #536 from jacobweinstock/k8s-client

Update kubernetes client creation for single namespace:

## Description

<!--- Please describe what this PR is going to change -->
Single namespace look ups weren't functioning properly. They function properly now.

## Why is this needed

<!--- Link to issue you have raised -->

Fixes: #

## How Has This Been Tested?
<!--- Please describe in detail how you tested your changes. -->
<!--- Include details of your testing environment, and the tests you ran to -->
<!--- see how your change affects other areas of the code, etc. -->


## How are existing users impacted? What migration steps/scripts do we need?

<!--- Fixes a bug, unblocks installation, removes a component of the stack etc -->
<!--- Requires a DB migration script, etc. -->


## Checklist:

I have:

- [ ] updated the documentation and/or roadmap (if required)
- [ ] added unit or e2e tests
- [ ] provided instructions on how to upgrade

cmd/smee/backend.go

@@ -8,9 +8,14 @@ import (
 	"github.com/tinkerbell/smee/internal/backend/kube"
 	"github.com/tinkerbell/smee/internal/backend/noop"
 	"github.com/tinkerbell/smee/internal/dhcp/handler"
+	"github.com/tinkerbell/tink/api/v1alpha1"
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/client-go/rest"
+	"k8s.io/client-go/scale/scheme"
 	"k8s.io/client-go/tools/clientcmd"
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
+	"sigs.k8s.io/controller-runtime/pkg/cache"
+	"sigs.k8s.io/controller-runtime/pkg/cluster"
 )
 
 type Kube struct {
@@ -38,26 +43,20 @@ func (n *Noop) backend() handler.BackendReader {
 }
 
 func (k *Kube) getClient() (*rest.Config, error) {
-	ccfg := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
-		&clientcmd.ClientConfigLoadingRules{
-			ExplicitPath: k.ConfigFilePath,
+	loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
+	loadingRules.ExplicitPath = k.ConfigFilePath
+
+	overrides := &clientcmd.ConfigOverrides{
+		ClusterInfo: clientcmdapi.Cluster{
+			Server: k.APIURL,
 		},
-		&clientcmd.ConfigOverrides{
-			ClusterInfo: clientcmdapi.Cluster{
-				Server: k.APIURL,
-			},
-			Context: clientcmdapi.Context{
-				Namespace: k.Namespace,
-			},
+		Context: clientcmdapi.Context{
+			Namespace: k.Namespace,
 		},
-	)
-
-	config, err := ccfg.ClientConfig()
-	if err != nil {
-		return nil, err
 	}
+	loader := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(loadingRules, overrides)
 
-	return config, nil
+	return loader.ClientConfig()
 }
 
 func (k *Kube) backend(ctx context.Context) (handler.BackendReader, error) {
@@ -66,7 +65,24 @@ func (k *Kube) backend(ctx context.Context) (handler.BackendReader, error) {
 		return nil, err
 	}
 
-	kb, err := kube.NewBackend(config)
+	rs := runtime.NewScheme()
+
+	if err := scheme.AddToScheme(rs); err != nil {
+		return nil, err
+	}
+
+	if err := v1alpha1.AddToScheme(rs); err != nil {
+		return nil, err
+	}
+
+	conf := func(opts *cluster.Options) {
+		opts.Scheme = rs
+		if k.Namespace != "" {
+			opts.Cache.DefaultNamespaces = map[string]cache.Config{k.Namespace: {}}
+		}
+	}
+
+	kb, err := kube.NewBackend(config, conf)
 	if err != nil {
 		return nil, err
 	}

internal/backend/kube/kube.go

@@ -14,8 +14,6 @@ import (
 	"github.com/tinkerbell/tink/api/v1alpha1"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/codes"
-	"k8s.io/apimachinery/pkg/runtime"
-	"k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/client-go/rest"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/cluster"
@@ -35,20 +33,7 @@ type Backend struct {
 //
 // Callers must instantiate the client-side cache by calling Start() before use.
 func NewBackend(conf *rest.Config, opts ...cluster.Option) (*Backend, error) {
-	rs := runtime.NewScheme()
-
-	if err := scheme.AddToScheme(rs); err != nil {
-		return nil, err
-	}
-
-	if err := v1alpha1.AddToScheme(rs); err != nil {
-		return nil, err
-	}
-
-	opts = append([]cluster.Option{func(o *cluster.Options) { o.Scheme = rs }}, opts...)
-	o := []cluster.Option{func(o *cluster.Options) { o.Scheme = rs }}
-	o = append(o, opts...)
-	c, err := cluster.New(conf, o...)
+	c, err := cluster.New(conf, opts...)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create new cluster config: %w", err)
 	}