registry/manifests.go
Stephen J Day c9aaff00f8
manifest: references should cover all children
To allow generic manifest walking, we define an interface method of
`References` that returns the referenced items in the manifest. The
current implementation does not return the config target from schema2,
making this useless for most applications.

The garbage collector has been modified to show the utility of this
correctly formed `References` method. We may be able to make more
generic traversal methods with this, as well.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
2016-10-18 11:43:33 -07:00

125 lines
4.2 KiB
Go

package distribution
import (
"fmt"
"mime"
"github.com/docker/distribution/context"
"github.com/docker/distribution/digest"
)
// Manifest represents a registry object specifying a set of
// references and an optional target
type Manifest interface {
// References returns a list of objects which make up this manifest.
// A reference is anything which can be represented by a
// distribution.Descriptor. These can consist of layers, resources or other
// manifests.
//
// While no particular order is required, implementations should return
// them from highest to lowest priority. For example, one might want to
// return the base layer before the top layer.
References() []Descriptor
// Payload provides the serialized format of the manifest, in addition to
// the mediatype.
Payload() (mediatype string, payload []byte, err error)
}
// ManifestBuilder creates a manifest allowing one to include dependencies.
// Instances can be obtained from a version-specific manifest package. Manifest
// specific data is passed into the function which creates the builder.
type ManifestBuilder interface {
// Build creates the manifest from his builder.
Build(ctx context.Context) (Manifest, error)
// References returns a list of objects which have been added to this
// builder. The dependencies are returned in the order they were added,
// which should be from base to head.
References() []Descriptor
// AppendReference includes the given object in the manifest after any
// existing dependencies. If the add fails, such as when adding an
// unsupported dependency, an error may be returned.
//
// The destination of the reference is dependent on the manifest type and
// the dependency type.
AppendReference(dependency Describable) error
}
// ManifestService describes operations on image manifests.
type ManifestService interface {
// Exists returns true if the manifest exists.
Exists(ctx context.Context, dgst digest.Digest) (bool, error)
// Get retrieves the manifest specified by the given digest
Get(ctx context.Context, dgst digest.Digest, options ...ManifestServiceOption) (Manifest, error)
// Put creates or updates the given manifest returning the manifest digest
Put(ctx context.Context, manifest Manifest, options ...ManifestServiceOption) (digest.Digest, error)
// Delete removes the manifest specified by the given digest. Deleting
// a manifest that doesn't exist will return ErrManifestNotFound
Delete(ctx context.Context, dgst digest.Digest) error
}
// ManifestEnumerator enables iterating over manifests
type ManifestEnumerator interface {
// Enumerate calls ingester for each manifest.
Enumerate(ctx context.Context, ingester func(digest.Digest) error) error
}
// Describable is an interface for descriptors
type Describable interface {
Descriptor() Descriptor
}
// ManifestMediaTypes returns the supported media types for manifests.
func ManifestMediaTypes() (mediaTypes []string) {
for t := range mappings {
if t != "" {
mediaTypes = append(mediaTypes, t)
}
}
return
}
// UnmarshalFunc implements manifest unmarshalling a given MediaType
type UnmarshalFunc func([]byte) (Manifest, Descriptor, error)
var mappings = make(map[string]UnmarshalFunc, 0)
// UnmarshalManifest looks up manifest unmarshal functions based on
// MediaType
func UnmarshalManifest(ctHeader string, p []byte) (Manifest, Descriptor, error) {
// Need to look up by the actual media type, not the raw contents of
// the header. Strip semicolons and anything following them.
var mediatype string
if ctHeader != "" {
var err error
mediatype, _, err = mime.ParseMediaType(ctHeader)
if err != nil {
return nil, Descriptor{}, err
}
}
unmarshalFunc, ok := mappings[mediatype]
if !ok {
unmarshalFunc, ok = mappings[""]
if !ok {
return nil, Descriptor{}, fmt.Errorf("unsupported manifest mediatype and no default available: %s", mediatype)
}
}
return unmarshalFunc(p)
}
// RegisterManifestSchema registers an UnmarshalFunc for a given schema type. This
// should be called from specific
func RegisterManifestSchema(mediatype string, u UnmarshalFunc) error {
if _, ok := mappings[mediatype]; ok {
return fmt.Errorf("manifest mediatype registration would overwrite existing: %s", mediatype)
}
mappings[mediatype] = u
return nil
}