Merge pull request moby#47023 from thaJeztah/fix_distribution_mirrors

api: fix "GET /distribution" endpoint ignoring mirrors

api/server/router/distribution/backend.go

@@ -11,5 +11,5 @@ import (
 // Backend is all the methods that need to be implemented
 // to provide image specific functionality.
 type Backend interface {
-	GetRepository(context.Context, reference.Named, *registry.AuthConfig) (distribution.Repository, error)
+	GetRepositories(context.Context, reference.Named, *registry.AuthConfig) ([]distribution.Repository, error)
 }

api/server/router/distribution/distribution_routes.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 
 	"github.com/distribution/reference"
+	"github.com/docker/distribution"
 	"github.com/docker/distribution/manifest/manifestlist"
 	"github.com/docker/distribution/manifest/schema1"
 	"github.com/docker/distribution/manifest/schema2"
@@ -42,24 +43,50 @@ func (s *distributionRouter) getDistributionInfo(ctx context.Context, w http.Res
 	// For a search it is not an error if no auth was given. Ignore invalid
 	// AuthConfig to increase compatibility with the existing API.
 	authConfig, _ := registry.DecodeAuthConfig(r.Header.Get(registry.AuthHeader))
-	distrepo, err := s.backend.GetRepository(ctx, namedRef, authConfig)
+	repos, err := s.backend.GetRepositories(ctx, namedRef, authConfig)
 	if err != nil {
 		return err
 	}
-	blobsrvc := distrepo.Blobs(ctx)
 
+	// Fetch the manifest; if a mirror is configured, try the mirror first,
+	// but continue with upstream on failure.
+	//
+	// FIXME(thaJeztah): construct "repositories" on-demand;
+	// GetRepositories() will attempt to connect to all endpoints (registries),
+	// but we may only need the first one if it contains the manifest we're
+	// looking for, or if the configured mirror is a pull-through mirror.
+	//
+	// Logic for this could be implemented similar to "distribution.Pull()",
+	// which uses the "pullEndpoints" utility to iterate over the list
+	// of endpoints;
+	//
+	// - https://github.com/moby/moby/blob/12c7411b6b7314bef130cd59f1c7384a7db06d0b/distribution/pull.go#L17-L31
+	// - https://github.com/moby/moby/blob/12c7411b6b7314bef130cd59f1c7384a7db06d0b/distribution/pull.go#L76-L152
+	var lastErr error
+	for _, repo := range repos {
+		distributionInspect, err := s.fetchManifest(ctx, repo, namedRef)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		return httputils.WriteJSON(w, http.StatusOK, distributionInspect)
+	}
+	return lastErr
+}
+
+func (s *distributionRouter) fetchManifest(ctx context.Context, distrepo distribution.Repository, namedRef reference.Named) (registry.DistributionInspect, error) {
 	var distributionInspect registry.DistributionInspect
 	if canonicalRef, ok := namedRef.(reference.Canonical); !ok {
 		namedRef = reference.TagNameOnly(namedRef)
 
 		taggedRef, ok := namedRef.(reference.NamedTagged)
 		if !ok {
-			return errdefs.InvalidParameter(errors.Errorf("image reference not tagged: %s", image))
+			return registry.DistributionInspect{}, errdefs.InvalidParameter(errors.Errorf("image reference not tagged: %s", namedRef))
 		}
 
 		descriptor, err := distrepo.Tags(ctx).Get(ctx, taggedRef.Tag())
 		if err != nil {
-			return err
+			return registry.DistributionInspect{}, err
 		}
 		distributionInspect.Descriptor = ocispec.Descriptor{
 			MediaType: descriptor.MediaType,
@@ -76,7 +103,7 @@ func (s *distributionRouter) getDistributionInfo(ctx context.Context, w http.Res
 	// we have a digest, so we can retrieve the manifest
 	mnfstsrvc, err := distrepo.Manifests(ctx)
 	if err != nil {
-		return err
+		return registry.DistributionInspect{}, err
 	}
 	mnfst, err := mnfstsrvc.Get(ctx, distributionInspect.Descriptor.Digest)
 	if err != nil {
@@ -88,14 +115,14 @@ func (s *distributionRouter) getDistributionInfo(ctx context.Context, w http.Res
 			reference.ErrNameEmpty,
 			reference.ErrNameTooLong,
 			reference.ErrNameNotCanonical:
-			return errdefs.InvalidParameter(err)
+			return registry.DistributionInspect{}, errdefs.InvalidParameter(err)
 		}
-		return err
+		return registry.DistributionInspect{}, err
 	}
 
 	mediaType, payload, err := mnfst.Payload()
 	if err != nil {
-		return err
+		return registry.DistributionInspect{}, err
 	}
 	// update MediaType because registry might return something incorrect
 	distributionInspect.Descriptor.MediaType = mediaType
@@ -116,7 +143,8 @@ func (s *distributionRouter) getDistributionInfo(ctx context.Context, w http.Res
 			})
 		}
 	case *schema2.DeserializedManifest:
-		configJSON, err := blobsrvc.Get(ctx, mnfstObj.Config.Digest)
+		blobStore := distrepo.Blobs(ctx)
+		configJSON, err := blobStore.Get(ctx, mnfstObj.Config.Digest)
 		var platform ocispec.Platform
 		if err == nil {
 			err := json.Unmarshal(configJSON, &platform)
@@ -131,6 +159,5 @@ func (s *distributionRouter) getDistributionInfo(ctx context.Context, w http.Res
 		}
 		distributionInspect.Platforms = append(distributionInspect.Platforms, platform)
 	}
-
-	return httputils.WriteJSON(w, http.StatusOK, distributionInspect)
+	return distributionInspect, nil
 }

daemon/cluster/executor/backend.go

@@ -78,5 +78,6 @@ type VolumeBackend interface {
 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/daemon.go

@@ -1595,3 +1595,19 @@ func (i *imageBackend) GetRepository(ctx context.Context, ref reference.Named, a
 		},
 	})
 }
+
+// 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
+// registries that were not reachable (pinging the /v2/ endpoint failed).
+//
+// 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 (i *imageBackend) GetRepositories(ctx context.Context, ref reference.Named, authConfig *registrytypes.AuthConfig) ([]dist.Repository, error) {
+	return distribution.GetRepositories(ctx, ref, &distribution.ImagePullConfig{
+		Config: distribution.Config{
+			AuthConfig:      authConfig,
+			RegistryService: i.registryService,
+		},
+	})
+}

distribution/repository.go

@@ -3,13 +3,33 @@ package distribution
 import (
 	"context"
 
+	"github.com/containerd/log"
 	"github.com/distribution/reference"
 	"github.com/docker/distribution"
 	"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
+// registries that were not reachable (pinging the /v2/ endpoint failed).
+//
+// 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)
@@ -24,11 +44,24 @@ func GetRepository(ctx context.Context, ref reference.Named, config *ImagePullCo
 		return nil, err
 	}
 
+	var (
+		repositories []distribution.Repository
+		lastError    error
+	)
 	for _, endpoint := range endpoints {
-		repository, lastError = newRepository(ctx, repoInfo, endpoint, nil, config.AuthConfig, "pull")
-		if lastError == nil {
-			break
+		repo, err := newRepository(ctx, repoInfo, endpoint, nil, config.AuthConfig, "pull")
+		if err != nil {
+			log.G(ctx).WithFields(log.Fields{"endpoint": endpoint.URL.String(), "error": err}).Info("endpoint")
+			lastError = err
+			continue
 		}
+		repositories = append(repositories, repo)
+		if firstOnly {
+			return repositories, nil
+		}
+	}
+	if len(repositories) == 0 {
+		return nil, lastError
 	}
-	return repository, lastError
+	return repositories, nil
 }