Use defaults package for listing namespace labels

Labels that are used for configuring defaults are moved to defaults package

Signed-off-by: Nikhil Soni <krsoninikhil@gmail.com>

client.go

@@ -144,7 +144,7 @@ func New(address string, opts ...ClientOpt) (*Client, error) {
 		namespaces := c.NamespaceService()
 		ctx := context.Background()
 		if labels, err := namespaces.Labels(ctx, copts.defaultns); err == nil {
-			if defaultRuntime, ok := labels["containerd.io/defaults/runtime"]; ok {
+			if defaultRuntime, ok := labels[defaults.DefaultRuntimeNSLabel]; ok {
 				c.runtime = defaultRuntime
 			}
 		} else {
@@ -174,7 +174,7 @@ func NewWithConn(conn *grpc.ClientConn, opts ...ClientOpt) (*Client, error) {
 		namespaces := c.NamespaceService()
 		ctx := context.Background()
 		if labels, err := namespaces.Labels(ctx, copts.defaultns); err == nil {
-			if defaultRuntime, ok := labels["containerd.io/defaults/runtime"]; ok {
+			if defaultRuntime, ok := labels[defaults.DefaultRuntimeNSLabel]; ok {
 				c.runtime = defaultRuntime
 			}
 		} else {

client_test.go

@@ -28,6 +28,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/containerd/containerd/defaults"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/namespaces"
@@ -405,7 +406,7 @@ func TestDefaultRuntimeWithNamespaceLabels(t *testing.T) {
 	defer cancel()
 	namespaces := client.NamespaceService()
 	testRuntime := "testRuntime"
-	runtimeLabel := "containerd.io/defaults/runtime"
+	runtimeLabel := defaults.DefaultRuntimeNSLabel
 	if err := namespaces.SetLabel(ctx, testNamespace, runtimeLabel, testRuntime); err != nil {
 		t.Fatal(err)
 	}

container_opts.go

@@ -20,6 +20,7 @@ import (
 	"context"
 
 	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/defaults"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/oci"
@@ -172,7 +173,7 @@ func setSnapshotterIfEmpty(ctx context.Context, client *Client, c *containers.Co
 		namespaceService := client.NamespaceService()
 		if ns, err := namespaces.NamespaceRequired(ctx); err == nil {
 			if labels, err := namespaceService.Labels(ctx, ns); err == nil {
-				if snapshotLabel, ok := labels["containerd.io/defaults/snapshotter"]; ok {
+				if snapshotLabel, ok := labels[defaults.DefaultSnapshotterNSLabel]; ok {
 					defaultSnapshotter = snapshotLabel
 				}
 			}

defaults/defaults.go

@@ -23,4 +23,10 @@ const (
 	// DefaultMaxSendMsgSize defines the default maximum message size for
 	// sending protobufs passed over the GRPC API.
 	DefaultMaxSendMsgSize = 16 << 20
+	// DefaultRuntimeNSLabel defines the namespace label to check for
+	// default runtime
+	DefaultRuntimeNSLabel = "containerd.io/defaults/runtime"
+	// DefaultSnapshotterNSLabel defines the namespances label to check for
+	// default snapshotter
+	DefaultSnapshotterNSLabel = "containerd.io/defaults/snapshotter"
 )