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v2_metadata_service.go
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v2_metadata_service.go
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package metadata
import (
"encoding/json"
"github.com/docker/distribution/digest"
"github.com/docker/docker/layer"
)
// V2MetadataService maps layer IDs to a set of known metadata for
// the layer.
type V2MetadataService struct {
store Store
}
// V2Metadata contains the digest and source repository information for a layer.
type V2Metadata struct {
Digest digest.Digest
SourceRepository string
}
// maxMetadata is the number of metadata entries to keep per layer DiffID.
const maxMetadata = 50
// NewV2MetadataService creates a new diff ID to v2 metadata mapping service.
func NewV2MetadataService(store Store) *V2MetadataService {
return &V2MetadataService{
store: store,
}
}
func (serv *V2MetadataService) diffIDNamespace() string {
return "v2metadata-by-diffid"
}
func (serv *V2MetadataService) digestNamespace() string {
return "diffid-by-digest"
}
func (serv *V2MetadataService) diffIDKey(diffID layer.DiffID) string {
return string(digest.Digest(diffID).Algorithm()) + "/" + digest.Digest(diffID).Hex()
}
func (serv *V2MetadataService) digestKey(dgst digest.Digest) string {
return string(dgst.Algorithm()) + "/" + dgst.Hex()
}
// GetMetadata finds the metadata associated with a layer DiffID.
func (serv *V2MetadataService) GetMetadata(diffID layer.DiffID) ([]V2Metadata, error) {
jsonBytes, err := serv.store.Get(serv.diffIDNamespace(), serv.diffIDKey(diffID))
if err != nil {
return nil, err
}
var metadata []V2Metadata
if err := json.Unmarshal(jsonBytes, &metadata); err != nil {
return nil, err
}
return metadata, nil
}
// GetDiffID finds a layer DiffID from a digest.
func (serv *V2MetadataService) GetDiffID(dgst digest.Digest) (layer.DiffID, error) {
diffIDBytes, err := serv.store.Get(serv.digestNamespace(), serv.digestKey(dgst))
if err != nil {
return layer.DiffID(""), err
}
return layer.DiffID(diffIDBytes), nil
}
// Add associates metadata with a layer DiffID. If too many metadata entries are
// present, the oldest one is dropped.
func (serv *V2MetadataService) Add(diffID layer.DiffID, metadata V2Metadata) error {
oldMetadata, err := serv.GetMetadata(diffID)
if err != nil {
oldMetadata = nil
}
newMetadata := make([]V2Metadata, 0, len(oldMetadata)+1)
// Copy all other metadata to new slice
for _, oldMeta := range oldMetadata {
if oldMeta != metadata {
newMetadata = append(newMetadata, oldMeta)
}
}
newMetadata = append(newMetadata, metadata)
if len(newMetadata) > maxMetadata {
newMetadata = newMetadata[len(newMetadata)-maxMetadata:]
}
jsonBytes, err := json.Marshal(newMetadata)
if err != nil {
return err
}
err = serv.store.Set(serv.diffIDNamespace(), serv.diffIDKey(diffID), jsonBytes)
if err != nil {
return err
}
return serv.store.Set(serv.digestNamespace(), serv.digestKey(metadata.Digest), []byte(diffID))
}
// Remove unassociates a metadata entry from a layer DiffID.
func (serv *V2MetadataService) Remove(metadata V2Metadata) error {
diffID, err := serv.GetDiffID(metadata.Digest)
if err != nil {
return err
}
oldMetadata, err := serv.GetMetadata(diffID)
if err != nil {
oldMetadata = nil
}
newMetadata := make([]V2Metadata, 0, len(oldMetadata))
// Copy all other metadata to new slice
for _, oldMeta := range oldMetadata {
if oldMeta != metadata {
newMetadata = append(newMetadata, oldMeta)
}
}
if len(newMetadata) == 0 {
return serv.store.Delete(serv.diffIDNamespace(), serv.diffIDKey(diffID))
}
jsonBytes, err := json.Marshal(newMetadata)
if err != nil {
return err
}
return serv.store.Set(serv.diffIDNamespace(), serv.diffIDKey(diffID), jsonBytes)
}