optimize memory usage in image load with Docker client integration

Signed-off-by: Kay Yan <kay.yan@daocloud.io>

Author: yankay

pkg/minikube/image/cache.go

@@ -17,10 +17,13 @@ limitations under the License.
 package image
 
 import (
+	"context"
+	"io"
 	"os"
 	"path/filepath"
 	"time"
 
+	"github.com/docker/docker/client"
 	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
@@ -84,7 +87,6 @@ func SaveToDir(images []string, cacheDir string, overwrite bool) error {
 	if err := g.Wait(); err != nil {
 		return errors.Wrap(err, "caching images")
 	}
-	klog.Infoln("Successfully saved all images to host disk.")
 	return nil
 }
 
@@ -158,6 +160,31 @@ func saveToTarFile(iname, rawDest string, overwrite bool) error {
 	return nil
 }
 
+func saveImageWithDockerClient(f *os.File, ref name.Reference) error {
+	cli, err := client.NewClientWithOpts(client.FromEnv)
+	if err != nil {
+		return errors.Wrap(err, "creating docker client")
+	}
+	defer cli.Close()
+
+	ctx := context.Background()
+
+	imageResponse, err := cli.ImageSave(ctx, []string{ref.String()})
+	if err != nil {
+		return errors.Wrap(err, "saving image via docker client")
+	}
+	defer imageResponse.Close()
+
+	// Copy image data stream to file
+	_, err = io.Copy(f, imageResponse)
+	if err != nil {
+		return errors.Wrap(err, "copying image data to file")
+	}
+
+	klog.Infof("Successfully saved image %s using Docker client", ref.String())
+	return nil
+}
+
 func writeImage(img v1.Image, dst string, ref name.Reference) error {
 	klog.Infoln("opening: ", dst)
 	f, err := os.CreateTemp(filepath.Dir(dst), filepath.Base(dst)+".*.tmp")
@@ -175,7 +202,12 @@ func writeImage(img v1.Image, dst string, ref name.Reference) error {
 		}
 	}()
 
-	err = tarball.Write(ref, img, f)
+	if useDaemon {
+		// Use Docker client to save image to file
+		err = saveImageWithDockerClient(f, ref)
+	} else {
+		err = tarball.Write(ref, img, f)
+	}
 	if err != nil {
 		return errors.Wrap(err, "write")
 	}

pkg/minikube/image/image.go

@@ -169,7 +169,7 @@ func retrieveImage(ref name.Reference, imgName string) (v1.Image, string, error)
 }
 
 func retrieveDaemon(ref name.Reference) (v1.Image, error) {
-	img, err := daemon.Image(ref, daemon.WithUnbufferedOpener())
+	img, err := daemon.Image(ref) // uses bufferedOpener, which may consume a significant amount of memory
 	if err == nil {
 		klog.Infof("found %s locally: %+v", ref.Name(), img)
 		return img, nil