distribution/storage/layerstore.go
Stephen J Day 68944ea9cf Clean up layer storage layout
Previously, discussions were still ongoing about different storage layouts that
could support various access models. This changeset removes a layer of
indirection that was in place due to earlier designs. Effectively, this both
associates a layer with a named repository and ensures that content cannot be
accessed across repositories. It also moves to rely on tarsum as a true
content-addressable identifier, removing a layer of indirection during blob
resolution.
2014-11-25 09:57:43 -08:00

129 lines
3.3 KiB
Go

package storage
import (
"time"
"github.com/docker/docker-registry/digest"
"github.com/docker/docker-registry/storagedriver"
)
type layerStore struct {
driver storagedriver.StorageDriver
pathMapper *pathMapper
uploadStore layerUploadStore
}
func (ls *layerStore) Exists(name string, digest digest.Digest) (bool, error) {
// Because this implementation just follows blob links, an existence check
// is pretty cheap by starting and closing a fetch.
_, err := ls.Fetch(name, digest)
if err != nil {
if err == ErrLayerUnknown {
return false, nil
}
return false, err
}
return true, nil
}
func (ls *layerStore) Fetch(name string, digest digest.Digest) (Layer, error) {
blobPath, err := ls.resolveBlobPath(name, digest)
if err != nil {
switch err := err.(type) {
case storagedriver.PathNotFoundError, *storagedriver.PathNotFoundError:
return nil, ErrLayerUnknown
default:
return nil, err
}
}
fr, err := newFileReader(ls.driver, blobPath)
if err != nil {
switch err := err.(type) {
case storagedriver.PathNotFoundError, *storagedriver.PathNotFoundError:
return nil, ErrLayerUnknown
default:
return nil, err
}
}
return &layerReader{
fileReader: *fr,
name: name,
digest: digest,
// TODO(stevvooe): Storage backend does not support modification time
// queries yet. Layers "never" change, so just return the zero value
// plus a nano-second.
createdAt: (time.Time{}).Add(time.Nanosecond),
}, nil
}
// Upload begins a layer upload, returning a handle. If the layer upload
// is already in progress or the layer has already been uploaded, this
// will return an error.
func (ls *layerStore) Upload(name string) (LayerUpload, error) {
// NOTE(stevvooe): Consider the issues with allowing concurrent upload of
// the same two layers. Should it be disallowed? For now, we allow both
// parties to proceed and the the first one uploads the layer.
lus, err := ls.uploadStore.New(name)
if err != nil {
return nil, err
}
return ls.newLayerUpload(lus), nil
}
// Resume continues an in progress layer upload, returning the current
// state of the upload.
func (ls *layerStore) Resume(uuid string) (LayerUpload, error) {
lus, err := ls.uploadStore.GetState(uuid)
if err != nil {
return nil, err
}
return ls.newLayerUpload(lus), nil
}
// newLayerUpload allocates a new upload controller with the given state.
func (ls *layerStore) newLayerUpload(lus LayerUploadState) LayerUpload {
return &layerUploadController{
LayerUploadState: lus,
layerStore: ls,
uploadStore: ls.uploadStore,
}
}
// resolveBlobId looks up the blob location in the repositories from a
// layer/blob link file, returning blob path or an error on failure.
func (ls *layerStore) resolveBlobPath(name string, dgst digest.Digest) (string, error) {
pathSpec := layerLinkPathSpec{name: name, digest: dgst}
layerLinkPath, err := ls.pathMapper.path(pathSpec)
if err != nil {
return "", err
}
layerLinkContent, err := ls.driver.GetContent(layerLinkPath)
if err != nil {
return "", err
}
// NOTE(stevvooe): The content of the layer link should match the digest.
// This layer of indirection is for name-based content protection.
linked, err := digest.ParseDigest(string(layerLinkContent))
if err != nil {
return "", err
}
bp := blobPathSpec{digest: linked}
return ls.pathMapper.path(bp)
}