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blobstore.go
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blobstore.go
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package storage
import (
"github.com/docker/distribution"
"github.com/docker/distribution/context"
"github.com/docker/distribution/digest"
"github.com/docker/distribution/registry/storage/driver"
)
// blobStore implements the read side of the blob store interface over a
// driver without enforcing per-repository membership. This object is
// intentionally a leaky abstraction, providing utility methods that support
// creating and traversing backend links.
type blobStore struct {
driver driver.StorageDriver
pm *pathMapper
statter distribution.BlobStatter
}
var _ distribution.BlobProvider = &blobStore{}
// Get implements the BlobReadService.Get call.
func (bs *blobStore) Get(ctx context.Context, dgst digest.Digest) ([]byte, error) {
bp, err := bs.path(dgst)
if err != nil {
return nil, err
}
p, err := bs.driver.GetContent(ctx, bp)
if err != nil {
switch err.(type) {
case driver.PathNotFoundError:
return nil, distribution.ErrBlobUnknown
}
return nil, err
}
return p, err
}
func (bs *blobStore) Open(ctx context.Context, dgst digest.Digest) (distribution.ReadSeekCloser, error) {
desc, err := bs.statter.Stat(ctx, dgst)
if err != nil {
return nil, err
}
path, err := bs.path(desc.Digest)
if err != nil {
return nil, err
}
return newFileReader(ctx, bs.driver, path, desc.Size)
}
// Put stores the content p in the blob store, calculating the digest. If the
// content is already present, only the digest will be returned. This should
// only be used for small objects, such as manifests. This implemented as a convenience for other Put implementations
func (bs *blobStore) Put(ctx context.Context, mediaType string, p []byte) (distribution.Descriptor, error) {
dgst, err := digest.FromBytes(p)
if err != nil {
context.GetLogger(ctx).Errorf("blobStore: error digesting content: %v, %s", err, string(p))
return distribution.Descriptor{}, err
}
desc, err := bs.statter.Stat(ctx, dgst)
if err == nil {
// content already present
return desc, nil
} else if err != distribution.ErrBlobUnknown {
context.GetLogger(ctx).Errorf("blobStore: error stating content (%v): %#v", dgst, err)
// real error, return it
return distribution.Descriptor{}, err
}
bp, err := bs.path(dgst)
if err != nil {
return distribution.Descriptor{}, err
}
// TODO(stevvooe): Write out mediatype here, as well.
return distribution.Descriptor{
Size: int64(len(p)),
// NOTE(stevvooe): The central blob store firewalls media types from
// other users. The caller should look this up and override the value
// for the specific repository.
MediaType: "application/octet-stream",
Digest: dgst,
}, bs.driver.PutContent(ctx, bp, p)
}
// path returns the canonical path for the blob identified by digest. The blob
// may or may not exist.
func (bs *blobStore) path(dgst digest.Digest) (string, error) {
bp, err := bs.pm.path(blobDataPathSpec{
digest: dgst,
})
if err != nil {
return "", err
}
return bp, nil
}
// link links the path to the provided digest by writing the digest into the
// target file. Caller must ensure that the blob actually exists.
func (bs *blobStore) link(ctx context.Context, path string, dgst digest.Digest) error {
// The contents of the "link" file are the exact string contents of the
// digest, which is specified in that package.
return bs.driver.PutContent(ctx, path, []byte(dgst))
}
// readlink returns the linked digest at path.
func (bs *blobStore) readlink(ctx context.Context, path string) (digest.Digest, error) {
content, err := bs.driver.GetContent(ctx, path)
if err != nil {
return "", err
}
linked, err := digest.ParseDigest(string(content))
if err != nil {
return "", err
}
return linked, nil
}
// resolve reads the digest link at path and returns the blob store path.
func (bs *blobStore) resolve(ctx context.Context, path string) (string, error) {
dgst, err := bs.readlink(ctx, path)
if err != nil {
return "", err
}
return bs.path(dgst)
}
type blobStatter struct {
driver driver.StorageDriver
pm *pathMapper
}
var _ distribution.BlobDescriptorService = &blobStatter{}
// Stat implements BlobStatter.Stat by returning the descriptor for the blob
// in the main blob store. If this method returns successfully, there is
// strong guarantee that the blob exists and is available.
func (bs *blobStatter) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
path, err := bs.pm.path(blobDataPathSpec{
digest: dgst,
})
if err != nil {
return distribution.Descriptor{}, err
}
fi, err := bs.driver.Stat(ctx, path)
if err != nil {
switch err := err.(type) {
case driver.PathNotFoundError:
return distribution.Descriptor{}, distribution.ErrBlobUnknown
default:
return distribution.Descriptor{}, err
}
}
if fi.IsDir() {
// NOTE(stevvooe): This represents a corruption situation. Somehow, we
// calculated a blob path and then detected a directory. We log the
// error and then error on the side of not knowing about the blob.
context.GetLogger(ctx).Warnf("blob path should not be a directory: %q", path)
return distribution.Descriptor{}, distribution.ErrBlobUnknown
}
// TODO(stevvooe): Add method to resolve the mediatype. We can store and
// cache a "global" media type for the blob, even if a specific repo has a
// mediatype that overrides the main one.
return distribution.Descriptor{
Size: fi.Size(),
// NOTE(stevvooe): The central blob store firewalls media types from
// other users. The caller should look this up and override the value
// for the specific repository.
MediaType: "application/octet-stream",
Digest: dgst,
}, nil
}
func (bs *blobStatter) Clear(ctx context.Context, dgst digest.Digest) error {
return distribution.ErrUnsupported
}
func (bs *blobStatter) SetDescriptor(ctx context.Context, dgst digest.Digest, desc distribution.Descriptor) error {
return distribution.ErrUnsupported
}