daemon/cluster: Cluster.imageWithDigestString: include mirrors to resolve digest

If the daemon is configured to use a mirror for the default (Docker Hub)
registry, the endpoint did not fall back to querying the upstream if the mirror
did not contain the given reference.

For pull-through registry-mirrors, this was not a problem, as in that case the
registry would forward the request, but for other mirrors, no fallback would
happen. This was inconsistent with how "pulling" images handled this situation;
when pulling images, both the mirror and upstream would be tried.

This patch brings the daemon-side lookup of image-manifests on-par with the
client-side lookup (the GET /distribution endpoint) as used in API 1.30 and
higher.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/cluster/executor/backend.go

@@ -77,7 +77,6 @@ type VolumeBackend interface {
 // ImageBackend is used by an executor to perform image operations
 type ImageBackend interface {
 	PullImage(ctx context.Context, ref reference.Named, platform *ocispec.Platform, metaHeaders map[string][]string, authConfig *registry.AuthConfig, outStream io.Writer) error
-	GetRepository(context.Context, reference.Named, *registry.AuthConfig) (distribution.Repository, error)
 	GetRepositories(context.Context, reference.Named, *registry.AuthConfig) ([]distribution.Repository, error)
 	GetImage(ctx context.Context, refOrID string, options opts.GetImageOpts) (*image.Image, error)
 }

daemon/cluster/services.go

@@ -25,6 +25,7 @@ import (
 	runconfigopts "github.com/docker/docker/runconfig/opts"
 	gogotypes "github.com/gogo/protobuf/types"
 	swarmapi "github.com/moby/swarmkit/v2/api"
+	"github.com/opencontainers/go-digest"
 	"github.com/pkg/errors"
 	"google.golang.org/grpc"
 )
@@ -635,16 +636,30 @@ func (c *Cluster) imageWithDigestString(ctx context.Context, image string, authC
 			return "", errors.Errorf("image reference not tagged: %s", image)
 		}
 
-		repo, err := c.config.ImageBackend.GetRepository(ctx, taggedRef, authConfig)
-		if err != nil {
-			return "", err
-		}
-		dscrptr, err := repo.Tags(ctx).Get(ctx, taggedRef.Tag())
+		// Fetch the image manifest's digest; if a mirror is configured, try the
+		// mirror first, but continue with upstream on failure.
+		repos, err := c.config.ImageBackend.GetRepositories(ctx, taggedRef, authConfig)
 		if err != nil {
 			return "", err
 		}
 
-		namedDigestedRef, err := reference.WithDigest(taggedRef, dscrptr.Digest)
+		var (
+			imgDigest digest.Digest
+			lastErr   error
+		)
+		for _, repo := range repos {
+			dscrptr, err := repo.Tags(ctx).Get(ctx, taggedRef.Tag())
+			if err != nil {
+				lastErr = err
+				continue
+			}
+			imgDigest = dscrptr.Digest
+		}
+		if lastErr != nil {
+			return "", lastErr
+		}
+
+		namedDigestedRef, err := reference.WithDigest(taggedRef, imgDigest)
 		if err != nil {
 			return "", err
 		}

daemon/daemon.go

@@ -1586,16 +1586,6 @@ type imageBackend struct {
 	registryService *registry.Service
 }
 
-// GetRepository returns a repository from the registry.
-func (i *imageBackend) GetRepository(ctx context.Context, ref reference.Named, authConfig *registrytypes.AuthConfig) (dist.Repository, error) {
-	return distribution.GetRepository(ctx, ref, &distribution.ImagePullConfig{
-		Config: distribution.Config{
-			AuthConfig:      authConfig,
-			RegistryService: i.registryService,
-		},
-	})
-}
-
 // GetRepositories returns a list of repositories configured for the given
 // reference. Multiple repositories can be returned if the reference is for
 // the default (Docker Hub) registry and a mirror is configured, but it omits

distribution/repository.go

@@ -9,15 +9,6 @@ import (
 	"github.com/docker/docker/errdefs"
 )
 
-// GetRepository returns a repository from the registry.
-func GetRepository(ctx context.Context, ref reference.Named, config *ImagePullConfig) (repository distribution.Repository, lastError error) {
-	repos, err := getRepositories(ctx, ref, config, true)
-	if len(repos) == 0 {
-		return nil, err
-	}
-	return repos[0], nil
-}
-
 // GetRepositories returns a list of repositories configured for the given
 // reference. Multiple repositories can be returned if the reference is for
 // the default (Docker Hub) registry and a mirror is configured, but it omits
@@ -26,10 +17,6 @@ func GetRepository(ctx context.Context, ref reference.Named, config *ImagePullCo
 // It returns an error if it was unable to reach any of the registries for
 // the given reference, or if the provided reference is invalid.
 func GetRepositories(ctx context.Context, ref reference.Named, config *ImagePullConfig) ([]distribution.Repository, error) {
-	return getRepositories(ctx, ref, config, false)
-}
-
-func getRepositories(ctx context.Context, ref reference.Named, config *ImagePullConfig, firstOnly bool) ([]distribution.Repository, error) {
 	repoInfo, err := config.RegistryService.ResolveRepository(ref)
 	if err != nil {
 		return nil, errdefs.InvalidParameter(err)
@@ -56,9 +43,6 @@ func getRepositories(ctx context.Context, ref reference.Named, config *ImagePull
 			continue
 		}
 		repositories = append(repositories, repo)
-		if firstOnly {
-			return repositories, nil
-		}
 	}
 	if len(repositories) == 0 {
 		return nil, lastError