pkg/specgen: cache image in generator

To prevent expensive redundant lookups and inspects on the same image,
cache the image in the generator.  Note that once a given image has been
inspected, subsequent calls will use the libimage-internal cache.

[NO TESTS NEEDED] since it is no functional change.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

2 files changed, 40 insertions, 21 deletions

diff --git a/pkg/specgen/generate/container.go b/pkg/specgen/generate/container.go
index 71b882510..f4b2eeb25 100644
--- a/pkg/specgen/generate/container.go
+++ b/pkg/specgen/generate/container.go
@@ -18,19 +18,43 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+func getImageFromSpec(ctx context.Context, r *libpod.Runtime, s *specgen.SpecGenerator) (*libimage.Image, string, *libimage.ImageData, error) {
+	if s.Image == "" || s.Rootfs != "" {
+		return nil, "", nil, nil
+	}
+
+	// Image may already have been set in the generator.
+	image, resolvedName := s.GetImage()
+	if image != nil {
+		inspectData, err := image.Inspect(ctx, false)
+		if err != nil {
+			return nil, "", nil, err
+		}
+		return image, resolvedName, inspectData, nil
+	}
+
+	// Need to look up image.
+	image, resolvedName, err := r.LibimageRuntime().LookupImage(s.Image, nil)
+	if err != nil {
+		return nil, "", nil, err
+	}
+	s.SetImage(image, resolvedName)
+	inspectData, err := image.Inspect(ctx, false)
+	if err != nil {
+		return nil, "", nil, err
+	}
+	return image, resolvedName, inspectData, err
+}
+
 // Fill any missing parts of the spec generator (e.g. from the image).
 // Returns a set of warnings or any fatal error that occurred.
 func CompleteSpec(ctx context.Context, r *libpod.Runtime, s *specgen.SpecGenerator) ([]string, error) {
 	// Only add image configuration if we have an image
-	var newImage *libimage.Image
-	var inspectData *libimage.ImageData
-	var err error
-	if s.Image != "" {
-		newImage, _, err = r.LibimageRuntime().LookupImage(s.Image, nil)
-		if err != nil {
-			return nil, err
-		}
-
+	newImage, _, inspectData, err := getImageFromSpec(ctx, r, s)
+	if err != nil {
+		return nil, err
+	}
+	if inspectData != nil {
 		inspectData, err = newImage.Inspect(ctx, false)
 		if err != nil {
 			return nil, err
diff --git a/pkg/specgen/generate/container_create.go b/pkg/specgen/generate/container_create.go
index 6100e7a5b..d0db9f35d 100644
--- a/pkg/specgen/generate/container_create.go
+++ b/pkg/specgen/generate/container_create.go
@@ -102,20 +102,15 @@ func MakeContainer(ctx context.Context, rt *libpod.Runtime, s *specgen.SpecGener
 		options = append(options, libpod.WithCreateCommand(s.ContainerCreateCommand))
 	}
 
-	var newImage *libimage.Image
-	var imageData *libimage.ImageData
 	if s.Rootfs != "" {
 		options = append(options, libpod.WithRootFS(s.Rootfs, s.RootfsOverlay))
-	} else {
-		var resolvedImageName string
-		newImage, resolvedImageName, err = rt.LibimageRuntime().LookupImage(s.Image, nil)
-		if err != nil {
-			return nil, nil, nil, err
-		}
-		imageData, err = newImage.Inspect(ctx, false)
-		if err != nil {
-			return nil, nil, nil, err
-		}
+	}
+
+	newImage, resolvedImageName, imageData, err := getImageFromSpec(ctx, rt, s)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	if newImage != nil {
 		// If the input name changed, we could properly resolve the
 		// image. Otherwise, it must have been an ID where we're
 		// defaulting to the first name or an empty one if no names are