Merge pull request #2135 from AkihiroSuda/oci-content-store

content: change Writer/ReaderAt to take OCI descriptor

client_test.go

@@ -214,7 +214,7 @@ func TestImagePullAllPlatforms(t *testing.T) {
 		}
 		// check if childless data type has blob in content store
 		for _, desc := range children {
-			ra, err := cs.ReaderAt(ctx, desc.Digest)
+			ra, err := cs.ReaderAt(ctx, desc)
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -275,7 +275,7 @@ func TestImagePullSomePlatforms(t *testing.T) {
 
 			// check if childless data type has blob in content store
 			for _, desc := range children {
-				ra, err := cs.ReaderAt(ctx, desc.Digest)
+				ra, err := cs.ReaderAt(ctx, desc)
 				if err != nil {
 					t.Fatal(err)
 				}

cmd/ctr/commands/content/content.go

@@ -72,7 +72,7 @@ var (
 			}
 			defer cancel()
 			cs := client.ContentStore()
-			ra, err := cs.ReaderAt(ctx, dgst)
+			ra, err := cs.ReaderAt(ctx, ocispec.Descriptor{Digest: dgst})
 			if err != nil {
 				return err
 			}
@@ -121,7 +121,7 @@ var (
 			// TODO(stevvooe): Allow ingest to be reentrant. Currently, we expect
 			// all data to be written in a single invocation. Allow multiple writes
 			// to the same transaction key followed by a commit.
-			return content.WriteBlob(ctx, cs, ref, os.Stdin, expectedSize, expectedDigest)
+			return content.WriteBlob(ctx, cs, ref, os.Stdin, ocispec.Descriptor{Size: expectedSize, Digest: expectedDigest})
 		},
 	}
 
@@ -314,7 +314,7 @@ var (
 			}
 			defer cancel()
 			cs := client.ContentStore()
-			ra, err := cs.ReaderAt(ctx, dgst)
+			ra, err := cs.ReaderAt(ctx, ocispec.Descriptor{Digest: dgst})
 			if err != nil {
 				return err
 			}
@@ -326,7 +326,7 @@ var (
 			}
 			defer nrc.Close()
 
-			wr, err := cs.Writer(ctx, "edit-"+object, 0, "") // TODO(stevvooe): Choose a better key?
+			wr, err := cs.Writer(ctx, content.WithRef("edit-"+object)) // TODO(stevvooe): Choose a better key?
 			if err != nil {
 				return err
 			}
@@ -482,7 +482,7 @@ var (
 				Size:      info.Size,
 			}
 
-			ra, err := cs.ReaderAt(ctx, dgst)
+			ra, err := cs.ReaderAt(ctx, desc)
 			if err != nil {
 				return err
 			}

cmd/ctr/commands/snapshots/snapshots.go

@@ -167,7 +167,7 @@ var diffCommand = cli.Command{
 			}
 		}
 
-		ra, err := client.ContentStore().ReaderAt(ctx, desc.Digest)
+		ra, err := client.ContentStore().ReaderAt(ctx, desc)
 		if err != nil {
 			return err
 		}

container_opts_unix.go

@@ -36,9 +36,9 @@ import (
 	"github.com/containerd/containerd/runtime/linux/runctypes"
 	"github.com/gogo/protobuf/proto"
 	protobuf "github.com/gogo/protobuf/types"
-	digest "github.com/opencontainers/go-digest"
 	"github.com/opencontainers/image-spec/identity"
 	"github.com/opencontainers/image-spec/specs-go/v1"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -50,10 +50,9 @@ func WithCheckpoint(im Image, snapshotKey string) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
 		var (
 			desc  = im.Target()
-			id    = desc.Digest
 			store = client.ContentStore()
 		)
-		index, err := decodeIndex(ctx, store, id)
+		index, err := decodeIndex(ctx, store, desc)
 		if err != nil {
 			return err
 		}
@@ -80,7 +79,7 @@ func WithCheckpoint(im Image, snapshotKey string) NewContainerOpts {
 				}
 				c.Image = index.Annotations["image.name"]
 			case images.MediaTypeContainerd1CheckpointConfig:
-				data, err := content.ReadBlob(ctx, store, m.Digest)
+				data, err := content.ReadBlob(ctx, store, m)
 				if err != nil {
 					return errors.Wrap(err, "unable to read checkpoint config")
 				}
@@ -113,7 +112,7 @@ func WithTaskCheckpoint(im Image) NewTaskOpts {
 	return func(ctx context.Context, c *Client, info *TaskInfo) error {
 		desc := im.Target()
 		id := desc.Digest
-		index, err := decodeIndex(ctx, c.ContentStore(), id)
+		index, err := decodeIndex(ctx, c.ContentStore(), desc)
 		if err != nil {
 			return err
 		}
@@ -131,9 +130,9 @@ func WithTaskCheckpoint(im Image) NewTaskOpts {
 	}
 }
 
-func decodeIndex(ctx context.Context, store content.Provider, id digest.Digest) (*v1.Index, error) {
+func decodeIndex(ctx context.Context, store content.Provider, desc ocispec.Descriptor) (*v1.Index, error) {
 	var index v1.Index
-	p, err := content.ReadBlob(ctx, store, id)
+	p, err := content.ReadBlob(ctx, store, desc)
 	if err != nil {
 		return nil, err
 	}

content/content.go

@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 // ReaderAt extends the standard io.ReaderAt interface with reporting of Size and io.Closer
@@ -33,12 +34,16 @@ type ReaderAt interface {
 
 // Provider provides a reader interface for specific content
 type Provider interface {
-	ReaderAt(ctx context.Context, dgst digest.Digest) (ReaderAt, error)
+	// ReaderAt only requires desc.Digest to be set.
+	// Other fields in the descriptor may be used internally for resolving
+	// the location of the actual data.
+	ReaderAt(ctx context.Context, dec ocispec.Descriptor) (ReaderAt, error)
 }
 
 // Ingester writes content
 type Ingester interface {
-	Writer(ctx context.Context, ref string, size int64, expected digest.Digest) (Writer, error)
+	// Some implementations require WithRef to be included in opts.
+	Writer(ctx context.Context, opts ...WriterOpt) (Writer, error)
 }
 
 // Info holds content specific information
@@ -142,3 +147,33 @@ func WithLabels(labels map[string]string) Opt {
 		return nil
 	}
 }
+
+// WriterOpts is internally used by WriterOpt.
+type WriterOpts struct {
+	Ref  string
+	Desc ocispec.Descriptor
+}
+
+// WriterOpt is used for passing options to Ingester.Writer.
+type WriterOpt func(*WriterOpts) error
+
+// WithDescriptor specifies an OCI descriptor.
+// Writer may optionally use the descriptor internally for resolving
+// the location of the actual data.
+// Write does not require any field of desc to be set.
+// If the data size is unknown, desc.Size should be set to 0.
+// Some implementations may also accept negative values as "unknown".
+func WithDescriptor(desc ocispec.Descriptor) WriterOpt {
+	return func(opts *WriterOpts) error {
+		opts.Desc = desc
+		return nil
+	}
+}
+
+// WithRef specifies a ref string.
+func WithRef(ref string) WriterOpt {
+	return func(opts *WriterOpts) error {
+		opts.Ref = ref
+		return nil
+	}
+}

content/helpers.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/containerd/containerd/errdefs"
 	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -45,8 +46,8 @@ func NewReader(ra ReaderAt) io.Reader {
 // ReadBlob retrieves the entire contents of the blob from the provider.
 //
 // Avoid using this for large blobs, such as layers.
-func ReadBlob(ctx context.Context, provider Provider, dgst digest.Digest) ([]byte, error) {
+func ReadBlob(ctx context.Context, provider Provider, desc ocispec.Descriptor) ([]byte, error) {
-	ra, err := provider.ReaderAt(ctx, dgst)
+	ra, err := provider.ReaderAt(ctx, desc)
 	if err != nil {
 		return nil, err
 	}
@@ -65,8 +66,8 @@ func ReadBlob(ctx context.Context, provider Provider, dgst digest.Digest) ([]byt
 // This is useful when the digest and size are known beforehand.
 //
 // Copy is buffered, so no need to wrap reader in buffered io.
-func WriteBlob(ctx context.Context, cs Ingester, ref string, r io.Reader, size int64, expected digest.Digest, opts ...Opt) error {
+func WriteBlob(ctx context.Context, cs Ingester, ref string, r io.Reader, desc ocispec.Descriptor, opts ...Opt) error {
-	cw, err := OpenWriter(ctx, cs, ref, size, expected)
+	cw, err := OpenWriter(ctx, cs, WithRef(ref), WithDescriptor(desc))
 	if err != nil {
 		if !errdefs.IsAlreadyExists(err) {
 			return err
@@ -76,19 +77,19 @@ func WriteBlob(ctx context.Context, cs Ingester, ref string, r io.Reader, size i
 	}
 	defer cw.Close()
 
-	return Copy(ctx, cw, r, size, expected, opts...)
+	return Copy(ctx, cw, r, desc.Size, desc.Digest, opts...)
 }
 
 // OpenWriter opens a new writer for the given reference, retrying if the writer
 // is locked until the reference is available or returns an error.
-func OpenWriter(ctx context.Context, cs Ingester, ref string, size int64, expected digest.Digest) (Writer, error) {
+func OpenWriter(ctx context.Context, cs Ingester, opts ...WriterOpt) (Writer, error) {
 	var (
 		cw    Writer
 		err   error
 		retry = 16
 	)
 	for {
-		cw, err = cs.Writer(ctx, ref, size, expected)
+		cw, err = cs.Writer(ctx, opts...)
 		if err != nil {
 			if !errdefs.IsUnavailable(err) {
 				return nil, err

content/local/store.go

@@ -34,6 +34,7 @@ import (
 	"github.com/containerd/containerd/filters"
 	"github.com/containerd/containerd/log"
 	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -119,15 +120,15 @@ func (s *store) info(dgst digest.Digest, fi os.FileInfo, labels map[string]strin
 }
 
 // ReaderAt returns an io.ReaderAt for the blob.
-func (s *store) ReaderAt(ctx context.Context, dgst digest.Digest) (content.ReaderAt, error) {
+func (s *store) ReaderAt(ctx context.Context, desc ocispec.Descriptor) (content.ReaderAt, error) {
-	p := s.blobPath(dgst)
+	p := s.blobPath(desc.Digest)
 	fi, err := os.Stat(p)
 	if err != nil {
 		if !os.IsNotExist(err) {
 			return nil, err
 		}
 
-		return nil, errors.Wrapf(errdefs.ErrNotFound, "blob %s expected at %s", dgst, p)
+		return nil, errors.Wrapf(errdefs.ErrNotFound, "blob %s expected at %s", desc.Digest, p)
 	}
 
 	fp, err := os.Open(p)
@@ -136,7 +137,7 @@ func (s *store) ReaderAt(ctx context.Context, dgst digest.Digest) (content.Reade
 			return nil, err
 		}
 
-		return nil, errors.Wrapf(errdefs.ErrNotFound, "blob %s expected at %s", dgst, p)
+		return nil, errors.Wrapf(errdefs.ErrNotFound, "blob %s expected at %s", desc.Digest, p)
 	}
 
 	return sizeReaderAt{size: fi.Size(), fp: fp}, nil
@@ -400,11 +401,22 @@ func (s *store) total(ingestPath string) int64 {
 // ref at a time.
 //
 // The argument `ref` is used to uniquely identify a long-lived writer transaction.
-func (s *store) Writer(ctx context.Context, ref string, total int64, expected digest.Digest) (content.Writer, error) {
+func (s *store) Writer(ctx context.Context, opts ...content.WriterOpt) (content.Writer, error) {
+	var wOpts content.WriterOpts
+	for _, opt := range opts {
+		if err := opt(&wOpts); err != nil {
+			return nil, err
+		}
+	}
+	// TODO(AkihiroSuda): we could create a random string or one calculated based on the context
+	// https://github.com/containerd/containerd/issues/2129#issuecomment-380255019
+	if wOpts.Ref == "" {
+		return nil, errors.Wrap(errdefs.ErrInvalidArgument, "ref must not be empty")
+	}
 	var lockErr error
 	for count := uint64(0); count < 10; count++ {
 		time.Sleep(time.Millisecond * time.Duration(rand.Intn(1<<count)))
-		if err := tryLock(ref); err != nil {
+		if err := tryLock(wOpts.Ref); err != nil {
 			if !errdefs.IsUnavailable(err) {
 				return nil, err
 			}
@@ -420,9 +432,9 @@ func (s *store) Writer(ctx context.Context, ref string, total int64, expected di
 		return nil, lockErr
 	}
 
-	w, err := s.writer(ctx, ref, total, expected)
+	w, err := s.writer(ctx, wOpts.Ref, wOpts.Desc.Size, wOpts.Desc.Digest)
 	if err != nil {
-		unlock(ref)
+		unlock(wOpts.Ref)
 		return nil, err
 	}
 

content/local/store_test.go

@@ -39,6 +39,7 @@ import (
 	"github.com/containerd/containerd/pkg/testutil"
 	"github.com/gotestyourself/gotestyourself/assert"
 	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 type memoryLabelStore struct {
@@ -108,7 +109,7 @@ func TestContentWriter(t *testing.T) {
 		t.Fatal("ingest dir should be created", err)
 	}
 
-	cw, err := cs.Writer(ctx, "myref", 0, "")
+	cw, err := cs.Writer(ctx, content.WithRef("myref"))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -117,13 +118,13 @@ func TestContentWriter(t *testing.T) {
 	}
 
 	// reopen, so we can test things
-	cw, err = cs.Writer(ctx, "myref", 0, "")
+	cw, err = cs.Writer(ctx, content.WithRef("myref"))
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	// make sure that second resume also fails
-	if _, err = cs.Writer(ctx, "myref", 0, ""); err == nil {
+	if _, err = cs.Writer(ctx, content.WithRef("myref")); err == nil {
 		// TODO(stevvooe): This also works across processes. Need to find a way
 		// to test that, as well.
 		t.Fatal("no error on second resume")
@@ -166,7 +167,7 @@ func TestContentWriter(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	cw, err = cs.Writer(ctx, "aref", 0, "")
+	cw, err = cs.Writer(ctx, content.WithRef("aref"))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -346,7 +347,8 @@ func checkBlobPath(t *testing.T, cs content.Store, dgst digest.Digest) string {
 }
 
 func checkWrite(ctx context.Context, t checker, cs content.Store, dgst digest.Digest, p []byte) digest.Digest {
-	if err := content.WriteBlob(ctx, cs, dgst.String(), bytes.NewReader(p), int64(len(p)), dgst); err != nil {
+	if err := content.WriteBlob(ctx, cs, dgst.String(), bytes.NewReader(p),
+		ocispec.Descriptor{Size: int64(len(p)), Digest: dgst}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -365,25 +367,25 @@ func TestWriterTruncateRecoversFromIncompleteWrite(t *testing.T) {
 	defer cancel()
 
 	ref := "ref"
-	content := []byte("this is the content")
+	contentB := []byte("this is the content")
-	total := int64(len(content))
+	total := int64(len(contentB))
 	setupIncompleteWrite(ctx, t, cs, ref, total)
 
-	writer, err := cs.Writer(ctx, ref, total, "")
+	writer, err := cs.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: total}))
 	assert.NilError(t, err)
 
 	assert.NilError(t, writer.Truncate(0))
 
-	_, err = writer.Write(content)
+	_, err = writer.Write(contentB)
 	assert.NilError(t, err)
 
-	dgst := digest.FromBytes(content)
+	dgst := digest.FromBytes(contentB)
 	err = writer.Commit(ctx, total, dgst)
 	assert.NilError(t, err)
 }
 
 func setupIncompleteWrite(ctx context.Context, t *testing.T, cs content.Store, ref string, total int64) {
-	writer, err := cs.Writer(ctx, ref, total, "")
+	writer, err := cs.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: total}))
 	assert.NilError(t, err)
 
 	_, err = writer.Write([]byte("bad data"))

content/proxy/content_store.go

@@ -25,6 +25,7 @@ import (
 	"github.com/containerd/containerd/errdefs"
 	protobuftypes "github.com/gogo/protobuf/types"
 	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 type proxyContentStore struct {
@@ -88,15 +89,16 @@ func (pcs *proxyContentStore) Delete(ctx context.Context, dgst digest.Digest) er
 	return nil
 }
 
-func (pcs *proxyContentStore) ReaderAt(ctx context.Context, dgst digest.Digest) (content.ReaderAt, error) {
+// ReaderAt ignores MediaType.
-	i, err := pcs.Info(ctx, dgst)
+func (pcs *proxyContentStore) ReaderAt(ctx context.Context, desc ocispec.Descriptor) (content.ReaderAt, error) {
+	i, err := pcs.Info(ctx, desc.Digest)
 	if err != nil {
 		return nil, err
 	}
 
 	return &remoteReaderAt{
 		ctx:    ctx,
-		digest: dgst,
+		digest: desc.Digest,
 		size:   i.Size,
 		client: pcs.client,
 	}, nil
@@ -157,14 +159,21 @@ func (pcs *proxyContentStore) ListStatuses(ctx context.Context, filters ...strin
 	return statuses, nil
 }
 
-func (pcs *proxyContentStore) Writer(ctx context.Context, ref string, size int64, expected digest.Digest) (content.Writer, error) {
+// Writer ignores MediaType.
-	wrclient, offset, err := pcs.negotiate(ctx, ref, size, expected)
+func (pcs *proxyContentStore) Writer(ctx context.Context, opts ...content.WriterOpt) (content.Writer, error) {
+	var wOpts content.WriterOpts
+	for _, opt := range opts {
+		if err := opt(&wOpts); err != nil {
+			return nil, err
+		}
+	}
+	wrclient, offset, err := pcs.negotiate(ctx, wOpts.Ref, wOpts.Desc.Size, wOpts.Desc.Digest)
 	if err != nil {
 		return nil, errdefs.FromGRPC(err)
 	}
 
 	return &remoteWriter{
-		ref:    ref,
+		ref:    wOpts.Ref,
 		client: wrclient,
 		offset: offset,
 	}, nil

content/testsuite/testsuite.go

@@ -33,6 +33,7 @@ import (
 	"github.com/containerd/containerd/pkg/testutil"
 	"github.com/gotestyourself/gotestyourself/assert"
 	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -122,28 +123,28 @@ var labels = map[string]string{
 
 func checkContentStoreWriter(ctx context.Context, t *testing.T, cs content.Store) {
 	c1, d1 := createContent(256)
-	w1, err := cs.Writer(ctx, "c1", 0, "")
+	w1, err := cs.Writer(ctx, content.WithRef("c1"))
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer w1.Close()
 
 	c2, d2 := createContent(256)
-	w2, err := cs.Writer(ctx, "c2", int64(len(c2)), "")
+	w2, err := cs.Writer(ctx, content.WithRef("c2"), content.WithDescriptor(ocispec.Descriptor{Size: int64(len(c2))}))
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer w2.Close()
 
 	c3, d3 := createContent(256)
-	w3, err := cs.Writer(ctx, "c3", 0, d3)
+	w3, err := cs.Writer(ctx, content.WithRef("c3"), content.WithDescriptor(ocispec.Descriptor{Digest: d3}))
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer w3.Close()
 
 	c4, d4 := createContent(256)
-	w4, err := cs.Writer(ctx, "c4", int64(len(c4)), d4)
+	w4, err := cs.Writer(ctx, content.WithRef("c4"), content.WithDescriptor(ocispec.Descriptor{Size: int64(len(c4)), Digest: d4}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -226,7 +227,7 @@ func checkResumeWriter(ctx context.Context, t *testing.T, cs content.Store) {
 	)
 
 	preStart := time.Now()
-	w1, err := cs.Writer(ctx, ref, 256, dgst)
+	w1, err := cs.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: 256, Digest: dgst}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -247,7 +248,7 @@ func checkResumeWriter(ctx context.Context, t *testing.T, cs content.Store) {
 	checkStatus(t, w1, expected, dgstFirst, preStart, postStart, preUpdate, postUpdate)
 	assert.NilError(t, w1.Close(), "close first writer")
 
-	w2, err := cs.Writer(ctx, ref, 256, dgst)
+	w2, err := cs.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: 256, Digest: dgst}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -284,7 +285,7 @@ func checkUpdateStatus(ctx context.Context, t *testing.T, cs content.Store) {
 	c1, d1 := createContent(256)
 
 	preStart := time.Now()
-	w1, err := cs.Writer(ctx, "c1", 256, d1)
+	w1, err := cs.Writer(ctx, content.WithRef("c1"), content.WithDescriptor(ocispec.Descriptor{Size: 256, Digest: d1}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -352,7 +353,7 @@ func checkUpdateStatus(ctx context.Context, t *testing.T, cs content.Store) {
 func checkLabels(ctx context.Context, t *testing.T, cs content.Store) {
 	c1, d1 := createContent(256)
 
-	w1, err := cs.Writer(ctx, "c1", 256, d1)
+	w1, err := cs.Writer(ctx, content.WithRef("c1"), content.WithDescriptor(ocispec.Descriptor{Size: 256, Digest: d1}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -427,7 +428,7 @@ func checkResume(rf func(context.Context, content.Writer, []byte, int64, int64,
 				limit := int64(float64(size) * tp)
 				ref := fmt.Sprintf("ref-%d-%d", i, j)
 
-				w, err := cs.Writer(ctx, ref, size, d)
+				w, err := cs.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: size, Digest: d}))
 				if err != nil {
 					t.Fatal(err)
 				}
@@ -441,7 +442,7 @@ func checkResume(rf func(context.Context, content.Writer, []byte, int64, int64,
 					t.Fatal(err)
 				}
 
-				w, err = cs.Writer(ctx, ref, size, d)
+				w, err = cs.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: size, Digest: d}))
 				if err != nil {
 					t.Fatal(err)
 				}
@@ -530,7 +531,7 @@ func checkSmallBlob(ctx context.Context, t *testing.T, store content.Store) {
 	blobSize := int64(len(blob))
 	blobDigest := digest.FromBytes(blob)
 	// test write
-	w, err := store.Writer(ctx, t.Name(), blobSize, blobDigest)
+	w, err := store.Writer(ctx, content.WithRef(t.Name()), content.WithDescriptor(ocispec.Descriptor{Size: blobSize, Digest: blobDigest}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -545,7 +546,7 @@ func checkSmallBlob(ctx context.Context, t *testing.T, store content.Store) {
 	}
 	// test read.
 	readSize := blobSize + 1
-	ra, err := store.ReaderAt(ctx, blobDigest)
+	ra, err := store.ReaderAt(ctx, ocispec.Descriptor{Digest: blobDigest})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -575,7 +576,7 @@ func checkCrossNSShare(ctx context.Context, t *testing.T, cs content.Store) {
 	ref := fmt.Sprintf("ref-%d", size)
 	t1 := time.Now()
 
-	if err := content.WriteBlob(ctx, cs, ref, bytes.NewReader(b), size, d); err != nil {
+	if err := content.WriteBlob(ctx, cs, ref, bytes.NewReader(b), ocispec.Descriptor{Size: size, Digest: d}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -585,7 +586,7 @@ func checkCrossNSShare(ctx context.Context, t *testing.T, cs content.Store) {
 	}
 	defer done(ctx2)
 
-	w, err := cs.Writer(ctx2, ref, size, d)
+	w, err := cs.Writer(ctx2, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: size, Digest: d}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -626,7 +627,7 @@ func checkCrossNSAppend(ctx context.Context, t *testing.T, cs content.Store) {
 	ref := fmt.Sprintf("ref-%d", size)
 	t1 := time.Now()
 
-	if err := content.WriteBlob(ctx, cs, ref, bytes.NewReader(b), size, d); err != nil {
+	if err := content.WriteBlob(ctx, cs, ref, bytes.NewReader(b), ocispec.Descriptor{Size: size, Digest: d}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -643,7 +644,7 @@ func checkCrossNSAppend(ctx context.Context, t *testing.T, cs content.Store) {
 	copy(b2[size:], extra)
 	d2 := digest.FromBytes(b2)
 
-	w, err := cs.Writer(ctx2, ref, size, d)
+	w, err := cs.Writer(ctx2, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{Size: size, Digest: d}))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -768,7 +769,7 @@ func checkContent(ctx context.Context, cs content.Store, d digest.Digest, expect
 		return err
 	}
 
-	b, err := content.ReadBlob(ctx, cs, d)
+	b, err := content.ReadBlob(ctx, cs, ocispec.Descriptor{Digest: d})
 	if err != nil {
 		return errors.Wrap(err, "failed to read blob")
 	}

diff/apply/apply.go

@@ -73,7 +73,7 @@ func (s *fsApplier) Apply(ctx context.Context, desc ocispec.Descriptor, mounts [
 
 	var ocidesc ocispec.Descriptor
 	if err := mount.WithTempMount(ctx, mounts, func(root string) error {
-		ra, err := s.store.ReaderAt(ctx, desc.Digest)
+		ra, err := s.store.ReaderAt(ctx, desc)
 		if err != nil {
 			return errors.Wrap(err, "failed to get reader from content store")
 		}

diff/walking/differ.go

@@ -86,7 +86,11 @@ func (s *walkingDiff) Compare(ctx context.Context, lower, upper []mount.Mount, o
 				config.Reference = uniqueRef()
 			}
 
-			cw, err := s.store.Writer(ctx, config.Reference, 0, "")
+			cw, err := s.store.Writer(ctx,
+				content.WithRef(config.Reference),
+				content.WithDescriptor(ocispec.Descriptor{
+					MediaType: config.MediaType, // most contentstore implementations just ignore this
+				}))
 			if err != nil {
 				return errors.Wrap(err, "failed to open writer")
 			}

diff/windows/windows.go

@@ -105,7 +105,7 @@ func (s windowsDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts
 		return emptyDesc, errors.Wrapf(errdefs.ErrNotImplemented, "unsupported diff media type: %v", desc.MediaType)
 	}
 
-	ra, err := s.store.ReaderAt(ctx, desc.Digest)
+	ra, err := s.store.ReaderAt(ctx, desc)
 	if err != nil {
 		return emptyDesc, errors.Wrap(err, "failed to get reader from content store")
 	}

images/image.go

@@ -143,7 +143,7 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 	if err := Walk(ctx, HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
 		switch desc.MediaType {
 		case MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
-			p, err := content.ReadBlob(ctx, provider, desc.Digest)
+			p, err := content.ReadBlob(ctx, provider, desc)
 			if err != nil {
 				return nil, err
 			}
@@ -159,7 +159,7 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 				}
 
 				if desc.Platform == nil {
-					p, err := content.ReadBlob(ctx, provider, manifest.Config.Digest)
+					p, err := content.ReadBlob(ctx, provider, manifest.Config)
 					if err != nil {
 						return nil, err
 					}
@@ -180,7 +180,7 @@ func Manifest(ctx context.Context, provider content.Provider, image ocispec.Desc
 
 			return nil, nil
 		case MediaTypeDockerSchema2ManifestList, ocispec.MediaTypeImageIndex:
-			p, err := content.ReadBlob(ctx, provider, desc.Digest)
+			p, err := content.ReadBlob(ctx, provider, desc)
 			if err != nil {
 				return nil, err
 			}
@@ -240,7 +240,7 @@ func Platforms(ctx context.Context, provider content.Provider, image ocispec.Des
 
 		switch desc.MediaType {
 		case MediaTypeDockerSchema2Config, ocispec.MediaTypeImageConfig:
-			p, err := content.ReadBlob(ctx, provider, desc.Digest)
+			p, err := content.ReadBlob(ctx, provider, desc)
 			if err != nil {
 				return nil, err
 			}
@@ -283,7 +283,7 @@ func Check(ctx context.Context, provider content.Provider, image ocispec.Descrip
 	required = append([]ocispec.Descriptor{mfst.Config}, mfst.Layers...)
 
 	for _, desc := range required {
-		ra, err := provider.ReaderAt(ctx, desc.Digest)
+		ra, err := provider.ReaderAt(ctx, desc)
 		if err != nil {
 			if errdefs.IsNotFound(err) {
 				missing = append(missing, desc)
@@ -305,7 +305,7 @@ func Children(ctx context.Context, provider content.Provider, desc ocispec.Descr
 	var descs []ocispec.Descriptor
 	switch desc.MediaType {
 	case MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
-		p, err := content.ReadBlob(ctx, provider, desc.Digest)
+		p, err := content.ReadBlob(ctx, provider, desc)
 		if err != nil {
 			return nil, err
 		}
@@ -320,7 +320,7 @@ func Children(ctx context.Context, provider content.Provider, desc ocispec.Descr
 		descs = append(descs, manifest.Config)
 		descs = append(descs, manifest.Layers...)
 	case MediaTypeDockerSchema2ManifestList, ocispec.MediaTypeImageIndex:
-		p, err := content.ReadBlob(ctx, provider, desc.Digest)
+		p, err := content.ReadBlob(ctx, provider, desc)
 		if err != nil {
 			return nil, err
 		}
@@ -351,7 +351,7 @@ func Children(ctx context.Context, provider content.Provider, desc ocispec.Descr
 // These are used to verify that a set of layers unpacked to the expected
 // values.
 func RootFS(ctx context.Context, provider content.Provider, configDesc ocispec.Descriptor) ([]digest.Digest, error) {
-	p, err := content.ReadBlob(ctx, provider, configDesc.Digest)
+	p, err := content.ReadBlob(ctx, provider, configDesc)
 	if err != nil {
 		return nil, err
 	}

images/oci/exporter.go

@@ -93,7 +93,7 @@ func blobRecord(cs content.Provider, desc ocispec.Descriptor) tarRecord {
 			Typeflag: tar.TypeReg,
 		},
 		CopyTo: func(ctx context.Context, w io.Writer) (int64, error) {
-			r, err := cs.ReaderAt(ctx, desc.Digest)
+			r, err := cs.ReaderAt(ctx, desc)
 			if err != nil {
 				return 0, err
 			}

images/oci/importer.go

@@ -140,7 +140,7 @@ func onUntarBlob(ctx context.Context, r io.Reader, store content.Ingester, name
 		return errors.Errorf("unsupported algorithm: %s", algo)
 	}
 	dgst := digest.NewDigestFromHex(algo.String(), split[2])
-	return content.WriteBlob(ctx, store, "unknown-"+dgst.String(), r, size, dgst)
+	return content.WriteBlob(ctx, store, "unknown-"+dgst.String(), r, ocispec.Descriptor{Size: size, Digest: dgst})
 }
 
 // GetChildrenDescriptors returns children blob descriptors for the following supported types:
@@ -175,7 +175,7 @@ func setGCRefContentLabels(ctx context.Context, store content.Store, desc ocispe
 		}
 		return err
 	}
-	ra, err := store.ReaderAt(ctx, desc.Digest)
+	ra, err := store.ReaderAt(ctx, desc)
 	if err != nil {
 		return err
 	}

metadata/content.go

@@ -32,6 +32,7 @@ import (
 	"github.com/containerd/containerd/metadata/boltutil"
 	"github.com/containerd/containerd/namespaces"
 	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -337,7 +338,18 @@ func (cs *contentStore) Abort(ctx context.Context, ref string) error {
 
 }
 
-func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expected digest.Digest) (content.Writer, error) {
+func (cs *contentStore) Writer(ctx context.Context, opts ...content.WriterOpt) (content.Writer, error) {
+	var wOpts content.WriterOpts
+	for _, opt := range opts {
+		if err := opt(&wOpts); err != nil {
+			return nil, err
+		}
+	}
+	// TODO(AkihiroSuda): we could create a random string or one calculated based on the context
+	// https://github.com/containerd/containerd/issues/2129#issuecomment-380255019
+	if wOpts.Ref == "" {
+		return nil, errors.Wrap(errdefs.ErrInvalidArgument, "ref must not be empty")
+	}
 	ns, err := namespaces.NamespaceRequired(ctx)
 	if err != nil {
 		return nil, err
@@ -353,12 +365,12 @@ func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expe
 	)
 	if err := update(ctx, cs.db, func(tx *bolt.Tx) error {
 		var shared bool
-		if expected != "" {
+		if wOpts.Desc.Digest != "" {
-			cbkt := getBlobBucket(tx, ns, expected)
+			cbkt := getBlobBucket(tx, ns, wOpts.Desc.Digest)
 			if cbkt != nil {
 				// Add content to lease to prevent other reference removals
 				// from effecting this object during a provided lease
-				if err := addContentLease(ctx, tx, expected); err != nil {
+				if err := addContentLease(ctx, tx, wOpts.Desc.Digest); err != nil {
 					return errors.Wrap(err, "unable to lease content")
 				}
 				// Return error outside of transaction to ensure
@@ -367,18 +379,18 @@ func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expe
 				return nil
 			}
 
-			if st, err := cs.Store.Info(ctx, expected); err == nil {
+			if st, err := cs.Store.Info(ctx, wOpts.Desc.Digest); err == nil {
 				// Ensure the expected size is the same, it is likely
 				// an error if the size is mismatched but the caller
 				// must resolve this on commit
-				if size == 0 || size == st.Size {
+				if wOpts.Desc.Size == 0 || wOpts.Desc.Size == st.Size {
 					shared = true
-					size = st.Size
+					wOpts.Desc.Size = st.Size
 				}
 			}
 		}
 
-		bkt, err := createIngestBucket(tx, ns, ref)
+		bkt, err := createIngestBucket(tx, ns, wOpts.Ref)
 		if err != nil {
 			return err
 		}
@@ -390,7 +402,7 @@ func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expe
 				return err
 			}
 
-			bref = createKey(sid, ns, ref)
+			bref = createKey(sid, ns, wOpts.Ref)
 			if err := bkt.Put(bucketKeyRef, []byte(bref)); err != nil {
 				return err
 			}
@@ -399,7 +411,7 @@ func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expe
 		}
 
 		if shared {
-			if err := bkt.Put(bucketKeyExpected, []byte(expected)); err != nil {
+			if err := bkt.Put(bucketKeyExpected, []byte(wOpts.Desc.Digest)); err != nil {
 				return err
 			}
 		} else {
@@ -407,19 +419,21 @@ func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expe
 			// already checked against the user metadata. The content must
 			// be committed in the namespace before it will be seen as
 			// available in the current namespace.
-			w, err = cs.Store.Writer(ctx, bref, size, "")
+			desc := wOpts.Desc
+			desc.Digest = ""
+			w, err = cs.Store.Writer(ctx, content.WithRef(bref), content.WithDescriptor(desc))
 		}
 		return err
 	}); err != nil {
 		return nil, err
 	}
 	if exists {
-		return nil, errors.Wrapf(errdefs.ErrAlreadyExists, "content %v", expected)
+		return nil, errors.Wrapf(errdefs.ErrAlreadyExists, "content %v", wOpts.Desc.Digest)
 	}
 
 	return &namespacedWriter{
 		ctx:       ctx,
-		ref:       ref,
+		ref:       wOpts.Ref,
 		namespace: ns,
 		db:        cs.db,
 		provider:  cs.Store,
@@ -427,8 +441,7 @@ func (cs *contentStore) Writer(ctx context.Context, ref string, size int64, expe
 		w:         w,
 		bref:      bref,
 		started:   time.Now(),
-		expected:  expected,
+		desc:      wOpts.Desc,
-		size:      size,
 	}, nil
 }
 
@@ -445,10 +458,9 @@ type namespacedWriter struct {
 
 	w content.Writer
 
-	bref     string
+	bref    string
-	started  time.Time
+	started time.Time
-	expected digest.Digest
+	desc    ocispec.Descriptor
-	size     int64
 }
 
 func (nw *namespacedWriter) Close() error {
@@ -465,7 +477,7 @@ func (nw *namespacedWriter) Write(p []byte) (int, error) {
 			return 0, nil
 		}
 
-		if err := nw.createAndCopy(nw.ctx, nw.size); err != nil {
+		if err := nw.createAndCopy(nw.ctx, nw.desc); err != nil {
 			return 0, err
 		}
 	}
@@ -477,31 +489,35 @@ func (nw *namespacedWriter) Digest() digest.Digest {
 	if nw.w != nil {
 		return nw.w.Digest()
 	}
-	return nw.expected
+	return nw.desc.Digest
 }
 
 func (nw *namespacedWriter) Truncate(size int64) error {
 	if nw.w != nil {
 		return nw.w.Truncate(size)
 	}
-
+	desc := nw.desc
-	return nw.createAndCopy(nw.ctx, size)
+	desc.Size = size
+	desc.Digest = ""
+	return nw.createAndCopy(nw.ctx, desc)
 }
 
-func (nw *namespacedWriter) createAndCopy(ctx context.Context, size int64) error {
+func (nw *namespacedWriter) createAndCopy(ctx context.Context, desc ocispec.Descriptor) error {
-	w, err := nw.provider.Writer(ctx, nw.bref, nw.size, "")
+	nwDescWithoutDigest := desc
+	nwDescWithoutDigest.Digest = ""
+	w, err := nw.provider.Writer(ctx, content.WithRef(nw.bref), content.WithDescriptor(nwDescWithoutDigest))
 	if err != nil {
 		return err
 	}
 
-	if size > 0 {
+	if desc.Size > 0 {
-		ra, err := nw.provider.ReaderAt(ctx, nw.expected)
+		ra, err := nw.provider.ReaderAt(ctx, nw.desc)
 		if err != nil {
 			return err
 		}
 		defer ra.Close()
 
-		if err := content.CopyReaderAt(w, ra, size); err != nil {
+		if err := content.CopyReaderAt(w, ra, desc.Size); err != nil {
 			nw.w.Close()
 			nw.w = nil
 			return err
@@ -544,14 +560,14 @@ func (nw *namespacedWriter) commit(ctx context.Context, tx *bolt.Tx, size int64,
 
 	var actual digest.Digest
 	if nw.w == nil {
-		if size != 0 && size != nw.size {
+		if size != 0 && size != nw.desc.Size {
-			return "", errors.Errorf("%q failed size validation: %v != %v", nw.ref, nw.size, size)
+			return "", errors.Errorf("%q failed size validation: %v != %v", nw.ref, nw.desc.Size, size)
 		}
-		if expected != "" && expected != nw.expected {
+		if expected != "" && expected != nw.desc.Digest {
 			return "", errors.Errorf("%q unexpected digest", nw.ref)
 		}
-		size = nw.size
+		size = nw.desc.Size
-		actual = nw.expected
+		actual = nw.desc.Digest
 		if getBlobBucket(tx, nw.namespace, actual) != nil {
 			return "", errors.Wrapf(errdefs.ErrAlreadyExists, "content %v", actual)
 		}
@@ -601,11 +617,11 @@ func (nw *namespacedWriter) Status() (st content.Status, err error) {
 	if nw.w != nil {
 		st, err = nw.w.Status()
 	} else {
-		st.Offset = nw.size
+		st.Offset = nw.desc.Size
-		st.Total = nw.size
+		st.Total = nw.desc.Size
 		st.StartedAt = nw.started
 		st.UpdatedAt = nw.started
-		st.Expected = nw.expected
+		st.Expected = nw.desc.Digest
 	}
 	if err == nil {
 		st.Ref = nw.ref
@@ -613,11 +629,11 @@ func (nw *namespacedWriter) Status() (st content.Status, err error) {
 	return
 }
 
-func (cs *contentStore) ReaderAt(ctx context.Context, dgst digest.Digest) (content.ReaderAt, error) {
+func (cs *contentStore) ReaderAt(ctx context.Context, desc ocispec.Descriptor) (content.ReaderAt, error) {
-	if err := cs.checkAccess(ctx, dgst); err != nil {
+	if err := cs.checkAccess(ctx, desc.Digest); err != nil {
 		return nil, err
 	}
-	return cs.Store.ReaderAt(ctx, dgst)
+	return cs.Store.ReaderAt(ctx, desc)
 }
 
 func (cs *contentStore) checkAccess(ctx context.Context, dgst digest.Digest) error {

metadata/content_test.go

@@ -32,6 +32,7 @@ import (
 	"github.com/containerd/containerd/leases"
 	"github.com/containerd/containerd/namespaces"
 	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 )
 
@@ -81,7 +82,8 @@ func TestContentLeased(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if err := content.WriteBlob(lctx, cs, "test-1", bytes.NewReader(blob), int64(len(blob)), expected); err != nil {
+	if err := content.WriteBlob(lctx, cs, "test-1", bytes.NewReader(blob),
+		ocispec.Descriptor{Size: int64(len(blob)), Digest: expected}); err != nil {
 		t.Fatal(err)
 	}
 	if err := checkContentLeased(lctx, db, expected); err != nil {
@@ -93,7 +95,9 @@ func TestContentLeased(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if _, err := cs.Writer(lctx, "test-2", int64(len(blob)), expected); err == nil {
+	if _, err := cs.Writer(lctx,
+		content.WithRef("test-2"),
+		content.WithDescriptor(ocispec.Descriptor{Size: int64(len(blob)), Digest: expected})); err == nil {
 		t.Fatal("expected already exist error")
 	} else if !errdefs.IsAlreadyExists(err) {
 		t.Fatal(err)

metadata/db_test.go

@@ -506,7 +506,9 @@ func create(obj object, tx *bolt.Tx, is images.Store, cs content.Store, sn snaps
 	case testContent:
 		ctx := WithTransactionContext(ctx, tx)
 		expected := digest.FromBytes(v.data)
-		w, err := cs.Writer(ctx, "test-ref", int64(len(v.data)), expected)
+		w, err := cs.Writer(ctx,
+			content.WithRef("test-ref"),
+			content.WithDescriptor(ocispec.Descriptor{Size: int64(len(v.data)), Digest: expected}))
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to create writer")
 		}

oci/spec_opts_unix.go

@@ -117,7 +117,7 @@ func WithImageConfig(image Image) SpecOpts {
 		)
 		switch ic.MediaType {
 		case v1.MediaTypeImageConfig, images.MediaTypeDockerSchema2Config:
-			p, err := content.ReadBlob(ctx, image.ContentStore(), ic.Digest)
+			p, err := content.ReadBlob(ctx, image.ContentStore(), ic)
 			if err != nil {
 				return err
 			}

oci/spec_opts_windows.go

@@ -44,7 +44,7 @@ func WithImageConfig(image Image) SpecOpts {
 		)
 		switch ic.MediaType {
 		case v1.MediaTypeImageConfig, images.MediaTypeDockerSchema2Config:
-			p, err := content.ReadBlob(ctx, image.ContentStore(), ic.Digest)
+			p, err := content.ReadBlob(ctx, image.ContentStore(), ic)
 			if err != nil {
 				return err
 			}

remotes/docker/schema1/converter.go

@@ -211,12 +211,12 @@ func (c *Converter) Convert(ctx context.Context, opts ...ConvertOpt) (ocispec.De
 	}
 
 	ref := remotes.MakeRefKey(ctx, desc)
-	if err := content.WriteBlob(ctx, c.contentStore, ref, bytes.NewReader(mb), desc.Size, desc.Digest, content.WithLabels(labels)); err != nil {
+	if err := content.WriteBlob(ctx, c.contentStore, ref, bytes.NewReader(mb), desc, content.WithLabels(labels)); err != nil {
 		return ocispec.Descriptor{}, errors.Wrap(err, "failed to write config")
 	}
 
 	ref = remotes.MakeRefKey(ctx, config)
-	if err := content.WriteBlob(ctx, c.contentStore, ref, bytes.NewReader(b), config.Size, config.Digest); err != nil {
+	if err := content.WriteBlob(ctx, c.contentStore, ref, bytes.NewReader(b), config); err != nil {
 		return ocispec.Descriptor{}, errors.Wrap(err, "failed to write config")
 	}
 
@@ -265,7 +265,7 @@ func (c *Converter) fetchBlob(ctx context.Context, desc ocispec.Descriptor) erro
 		size = 0
 	}
 
-	cw, err := content.OpenWriter(ctx, c.contentStore, ref, size, desc.Digest)
+	cw, err := content.OpenWriter(ctx, c.contentStore, content.WithRef(ref), content.WithDescriptor(desc))
 	if err != nil {
 		if !errdefs.IsAlreadyExists(err) {
 			return err
@@ -274,7 +274,7 @@ func (c *Converter) fetchBlob(ctx context.Context, desc ocispec.Descriptor) erro
 		// TODO: Check if blob -> diff id mapping already exists
 		// TODO: Check if blob empty label exists
 
-		ra, err := c.contentStore.ReaderAt(ctx, desc.Digest)
+		ra, err := c.contentStore.ReaderAt(ctx, desc)
 		if err != nil {
 			return err
 		}

remotes/handlers.go

@@ -81,7 +81,7 @@ func FetchHandler(ingester content.Ingester, fetcher Fetcher) images.HandlerFunc
 func fetch(ctx context.Context, ingester content.Ingester, fetcher Fetcher, desc ocispec.Descriptor) error {
 	log.G(ctx).Debug("fetch")
 
-	cw, err := content.OpenWriter(ctx, ingester, MakeRefKey(ctx, desc), desc.Size, desc.Digest)
+	cw, err := content.OpenWriter(ctx, ingester, content.WithRef(MakeRefKey(ctx, desc)), content.WithDescriptor(desc))
 	if err != nil {
 		if errdefs.IsAlreadyExists(err) {
 			return nil
@@ -141,7 +141,7 @@ func push(ctx context.Context, provider content.Provider, pusher Pusher, desc oc
 	}
 	defer cw.Close()
 
-	ra, err := provider.ReaderAt(ctx, desc.Digest)
+	ra, err := provider.ReaderAt(ctx, desc)
 	if err != nil {
 		return err
 	}

services/content/service.go

@@ -29,6 +29,7 @@ import (
 	"github.com/containerd/containerd/services"
 	ptypes "github.com/gogo/protobuf/types"
 	digest "github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"google.golang.org/grpc"
@@ -179,7 +180,7 @@ func (s *service) Read(req *api.ReadContentRequest, session api.Content_ReadServ
 		return errdefs.ToGRPC(err)
 	}
 
-	ra, err := s.store.ReaderAt(session.Context(), req.Digest)
+	ra, err := s.store.ReaderAt(session.Context(), ocispec.Descriptor{Digest: req.Digest})
 	if err != nil {
 		return errdefs.ToGRPC(err)
 	}
@@ -334,7 +335,9 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 
 	log.G(ctx).Debug("(*service).Write started")
 	// this action locks the writer for the session.
-	wr, err := s.store.Writer(ctx, ref, total, expected)
+	wr, err := s.store.Writer(ctx,
+		content.WithRef(ref),
+		content.WithDescriptor(ocispec.Descriptor{Size: total, Digest: expected}))
 	if err != nil {
 		return errdefs.ToGRPC(err)
 	}

services/tasks/local.go

@@ -45,6 +45,7 @@ import (
 	"github.com/containerd/containerd/services"
 	"github.com/containerd/typeurl"
 	ptypes "github.com/gogo/protobuf/types"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
@@ -121,7 +122,11 @@ func (l *local) Create(ctx context.Context, r *api.CreateTaskRequest, _ ...grpc.
 		if r.Checkpoint.MediaType != images.MediaTypeContainerd1Checkpoint {
 			return nil, fmt.Errorf("unsupported checkpoint type %q", r.Checkpoint.MediaType)
 		}
-		reader, err := l.store.ReaderAt(ctx, r.Checkpoint.Digest)
+		reader, err := l.store.ReaderAt(ctx, ocispec.Descriptor{
+			MediaType: r.Checkpoint.MediaType,
+			Digest:    r.Checkpoint.Digest,
+			Size:      r.Checkpoint.Size_,
+		})
 		if err != nil {
 			return nil, err
 		}
@@ -573,7 +578,7 @@ func getTasksMetrics(ctx context.Context, filter filters.Filter, tasks []runtime
 }
 
 func (l *local) writeContent(ctx context.Context, mediaType, ref string, r io.Reader) (*types.Descriptor, error) {
-	writer, err := l.store.Writer(ctx, ref, 0, "")
+	writer, err := l.store.Writer(ctx, content.WithRef(ref), content.WithDescriptor(ocispec.Descriptor{MediaType: mediaType}))
 	if err != nil {
 		return nil, err
 	}

task.go

@@ -597,7 +597,7 @@ func (t *task) writeIndex(ctx context.Context, index *v1.Index) (d v1.Descriptor
 }
 
 func writeContent(ctx context.Context, store content.Ingester, mediaType, ref string, r io.Reader, opts ...content.Opt) (d v1.Descriptor, err error) {
-	writer, err := store.Writer(ctx, ref, 0, "")
+	writer, err := store.Writer(ctx, content.WithRef(ref))
 	if err != nil {
 		return d, err
 	}

vendor.conf

@@ -43,8 +43,8 @@ github.com/syndtr/gocapability db04d3cc01c8b54962a58ec7e491717d06cfcc16
 github.com/gotestyourself/gotestyourself 44dbf532bbf5767611f6f2a61bded572e337010a
 github.com/google/go-cmp v0.1.0
 
-# cri dependencies
+# #2135: cri is temporarily forked because of circular dependency. will be fixed immediately in a follow-up PR.
-github.com/containerd/cri b68fb075d49aa1c2885f45f2467142666c244f4a
+github.com/containerd/cri 6e975823be192ad19f2ce7afcf6c57b88a991c30 https://github.com/AkihiroSuda/cri-containerd.git
 github.com/containerd/go-cni f2d7272f12d045b16ed924f50e91f9f9cecc55a7
 github.com/blang/semver v3.1.0
 github.com/containernetworking/cni v0.6.0

vendor/github.com/containerd/cri/pkg/containerd/importer/importer.go

@@ -254,23 +254,24 @@ func writeDockerSchema2Manifest(ctx context.Context, cs content.Ingester, manife
 	for i, ch := range manifest.Layers {
 		labels[fmt.Sprintf("containerd.io/gc.ref.content.%d", i+1)] = ch.Digest.String()
 	}
-	if err := content.WriteBlob(ctx, cs, "manifest-"+manifestDigest.String(), manifestBytesR,
-		int64(len(manifestBytes)), manifestDigest, content.WithLabels(labels)); err != nil {
-		return nil, err
-	}
 
-	desc := &ocispec.Descriptor{
+	desc := ocispec.Descriptor{
 		MediaType: images.MediaTypeDockerSchema2Manifest,
 		Digest:    manifestDigest,
 		Size:      int64(len(manifestBytes)),
 	}
+	if err := content.WriteBlob(ctx, cs, "manifest-"+manifestDigest.String(), manifestBytesR,
+		desc, content.WithLabels(labels)); err != nil {
+		return nil, err
+	}
+
 	if arch != "" || os != "" {
 		desc.Platform = &ocispec.Platform{
 			Architecture: arch,
 			OS:           os,
 		}
 	}
-	return desc, nil
+	return &desc, nil
 }
 
 func onUntarManifestJSON(r io.Reader) ([]manifestDotJSON, error) {
@@ -290,7 +291,7 @@ func onUntarLayerTar(ctx context.Context, r io.Reader, cs content.Ingester, name
 	// name is like "foobar/layer.tar" ( guaranteed by isLayerTar() )
 	split := strings.Split(name, "/")
 	// note: split[0] is not expected digest here
-	cw, err := cs.Writer(ctx, "layer-"+split[0], size, "")
+	cw, err := cs.Writer(ctx, content.WithRef("layer-"+split[0]), content.WithDescriptor(ocispec.Descriptor{Size: size}))
 	if err != nil {
 		return nil, err
 	}
@@ -311,7 +312,7 @@ func onUntarDotJSON(ctx context.Context, r io.Reader, cs content.Ingester, name
 	config.desc.Size = size
 	// name is like "foobar.json" ( guaranteed by is DotJSON() )
 	split := strings.Split(name, ".")
-	cw, err := cs.Writer(ctx, "config-"+split[0], size, "")
+	cw, err := cs.Writer(ctx, content.WithRef("config-"+split[0]), content.WithDescriptor(ocispec.Descriptor{Size: size}))
 	if err != nil {
 		return nil, err
 	}

vendor/github.com/containerd/cri/pkg/server/events.go

@@ -116,15 +116,16 @@ func convertEvent(e *gogotypes.Any) (string, interface{}, error) {
 }
 
 // start starts the event monitor which monitors and handles all container events. It returns
-// a channel for the caller to wait for the event monitor to stop. start must be called after
+// an error channel for the caller to wait for stop errors from the event monitor.
-// subscribe.
+// start must be called after subscribe.
-func (em *eventMonitor) start() (<-chan struct{}, error) {
+func (em *eventMonitor) start() <-chan error {
+	errCh := make(chan error)
 	if em.ch == nil || em.errCh == nil {
-		return nil, errors.New("event channel is nil")
+		panic("event channel is nil")
 	}
-	closeCh := make(chan struct{})
 	backOffCheckCh := em.backOff.start()
 	go func() {
+		defer close(errCh)
 		for {
 			select {
 			case e := <-em.ch:
@@ -144,8 +145,11 @@ func (em *eventMonitor) start() (<-chan struct{}, error) {
 					em.backOff.enBackOff(cID, evt)
 				}
 			case err := <-em.errCh:
-				logrus.WithError(err).Error("Failed to handle event stream")
+				// Close errCh in defer directly if there is no error.
-				close(closeCh)
+				if err != nil {
+					logrus.WithError(err).Errorf("Failed to handle event stream")
+					errCh <- err
+				}
 				return
 			case <-backOffCheckCh:
 				cIDs := em.backOff.getExpiredContainers()
@@ -162,7 +166,7 @@ func (em *eventMonitor) start() (<-chan struct{}, error) {
 			}
 		}
 	}()
-	return closeCh, nil
+	return errCh
 }
 
 // stop stops the event monitor. It will close the event channel.

vendor/github.com/containerd/cri/pkg/server/helpers.go

@@ -345,7 +345,7 @@ func getImageInfo(ctx context.Context, image containerd.Image) (*imageInfo, erro
 	}
 	id := desc.Digest.String()
 
-	rb, err := content.ReadBlob(ctx, image.ContentStore(), desc.Digest)
+	rb, err := content.ReadBlob(ctx, image.ContentStore(), desc)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to read image config from content store")
 	}

vendor/github.com/containerd/cri/pkg/server/service.go

@@ -19,6 +19,7 @@ package server
 import (
 	"fmt"
 	"io"
+	"net/http"
 	"path/filepath"
 	"time"
 
@@ -179,10 +180,7 @@ func (c *criService) Run() error {
 
 	// Start event handler.
 	logrus.Info("Start event monitor")
-	eventMonitorCloseCh, err := c.eventMonitor.start()
+	eventMonitorErrCh := c.eventMonitor.start()
-	if err != nil {
-		return errors.Wrap(err, "failed to start event monitor")
-	}
 
 	// Start snapshot stats syncer, it doesn't need to be stopped.
 	logrus.Info("Start snapshots syncer")
@@ -195,27 +193,32 @@ func (c *criService) Run() error {
 
 	// Start streaming server.
 	logrus.Info("Start streaming server")
-	streamServerCloseCh := make(chan struct{})
+	streamServerErrCh := make(chan error)
 	go func() {
-		if err := c.streamServer.Start(true); err != nil {
+		defer close(streamServerErrCh)
+		if err := c.streamServer.Start(true); err != nil && err != http.ErrServerClosed {
 			logrus.WithError(err).Error("Failed to start streaming server")
+			streamServerErrCh <- err
 		}
-		close(streamServerCloseCh)
 	}()
 
 	// Set the server as initialized. GRPC services could start serving traffic.
 	c.initialized.Set()
 
+	var eventMonitorErr, streamServerErr error
 	// Stop the whole CRI service if any of the critical service exits.
 	select {
-	case <-eventMonitorCloseCh:
+	case eventMonitorErr = <-eventMonitorErrCh:
-	case <-streamServerCloseCh:
+	case streamServerErr = <-streamServerErrCh:
 	}
 	if err := c.Close(); err != nil {
 		return errors.Wrap(err, "failed to stop cri service")
 	}
-
+	// If the error is set above, err from channel must be nil here, because
-	<-eventMonitorCloseCh
+	// the channel is supposed to be closed. Or else, we wait and set it.
+	if err := <-eventMonitorErrCh; err != nil {
+		eventMonitorErr = err
+	}
 	logrus.Info("Event monitor stopped")
 	// There is a race condition with http.Server.Serve.
 	// When `Close` is called at the same time with `Serve`, `Close`
@@ -227,18 +230,27 @@ func (c *criService) Run() error {
 	// is fixed.
 	const streamServerStopTimeout = 2 * time.Second
 	select {
-	case <-streamServerCloseCh:
+	case err := <-streamServerErrCh:
+		if err != nil {
+			streamServerErr = err
+		}
 		logrus.Info("Stream server stopped")
 	case <-time.After(streamServerStopTimeout):
 		logrus.Errorf("Stream server is not stopped in %q", streamServerStopTimeout)
 	}
+	if eventMonitorErr != nil {
+		return errors.Wrap(eventMonitorErr, "event monitor error")
+	}
+	if streamServerErr != nil {
+		return errors.Wrap(streamServerErr, "stream server error")
+	}
 	return nil
 }
 
-// Stop stops the CRI service.
+// Close stops the CRI service.
+// TODO(random-liu): Make close synchronous.
 func (c *criService) Close() error {
 	logrus.Info("Stop CRI service")
-	// TODO(random-liu): Make event monitor stop synchronous.
 	c.eventMonitor.stop()
 	if err := c.streamServer.Stop(); err != nil {
 		return errors.Wrap(err, "failed to stop stream server")

vendor/github.com/containerd/cri/vendor.conf

@@ -4,7 +4,7 @@ github.com/boltdb/bolt e9cf4fae01b5a8ff89d0ec6b32f0d9c9f79aefdd
 github.com/BurntSushi/toml a368813c5e648fee92e5f6c30e3944ff9d5e8895
 github.com/containerd/cgroups fe281dd265766145e943a034aa41086474ea6130
 github.com/containerd/console cb7008ab3d8359b78c5f464cb7cf160107ad5925
-github.com/containerd/containerd 1e8b09cfc6825f7e6349884b5f76e86c1f04a5d4
+github.com/containerd/containerd 1f8c612a6c7ef2fc8328c953fb660adce2bf0a80 https://github.com/AkihiroSuda/containerd.git
 github.com/containerd/continuity 2d3749b4da569ac97ca63dccba5eee4f5ee2beab
 github.com/containerd/fifo 3d5202aec260678c48179c56f40e6f38a095738c
 github.com/containerd/go-cni f2d7272f12d045b16ed924f50e91f9f9cecc55a7