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content: remove Provider.Reader

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After some analysis, it was found that Content.Reader was generally
redudant to an io.ReaderAt. This change removes `Content.Reader` in
favor of a `Content.ReaderAt`. In general, `ReaderAt` can perform better
over interfaces with indeterminant latency because it avoids remote
state for reads. Where a reader is required, a helper is provided to
convert it into an `io.SectionReader`.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2017-07-27 19:07:58 -07:00
parent 1f04eddad1
commit 8be340e37b
No known key found for this signature in database
GPG Key ID: 67B3DED84EDC823F
19 changed files with 105 additions and 152 deletions
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16
cmd/ctr/content.go
View File

@ -54,13 +54,13 @@ var (
return err
}
rc, err := cs.Reader(ctx, dgst)
ra, err := cs.ReaderAt(ctx, dgst)
if err != nil {
return err
}
defer rc.Close()
defer ra.Close()
_, err = io.Copy(os.Stdout, rc)
_, err = io.Copy(os.Stdout, content.NewReader(ra))
return err
},
}
@ -306,24 +306,24 @@ var (
return err
}
content, err := getContentStore(context)
cs, err := getContentStore(context)
if err != nil {
return err
}
rc, err := content.Reader(ctx, dgst)
ra, err := cs.ReaderAt(ctx, dgst)
if err != nil {
return err
}
defer rc.Close()
defer ra.Close()
nrc, err := edit(rc)
nrc, err := edit(content.NewReader(ra))
if err != nil {
return err
}
defer nrc.Close()
wr, err := content.Writer(ctx, "edit-"+object, 0, "") // TODO(stevvooe): Choose a better key?
wr, err := cs.Writer(ctx, "edit-"+object, 0, "") // TODO(stevvooe): Choose a better key?
if err != nil {
return err
}

6
cmd/ctr/pushobject.go
View File

@ -58,11 +58,11 @@ var pushObjectCommand = cli.Command{
Size: info.Size,
}
rc, err := cs.Reader(ctx, dgst)
ra, err := cs.ReaderAt(ctx, dgst)
if err != nil {
return err
}
defer rc.Close()
defer ra.Close()
cw, err := pusher.Push(ctx, desc)
if err != nil {
@ -70,7 +70,7 @@ var pushObjectCommand = cli.Command{
}
// TODO: Progress reader
if err := content.Copy(cw, rc, desc.Size, desc.Digest); err != nil {
if err := content.Copy(cw, content.NewReader(ra), desc.Size, desc.Digest); err != nil {
return err
}

18
container_opts_unix.go
View File

@ -6,7 +6,6 @@ import (
"context"
"encoding/json"
"fmt"
"io/ioutil"
"github.com/containerd/containerd/api/types"
"github.com/containerd/containerd/containers"
@ -54,12 +53,7 @@ func WithCheckpoint(desc v1.Descriptor, rootfsID string) NewContainerOpts {
}
c.Image = index.Annotations["image.name"]
case images.MediaTypeContainerd1CheckpointConfig:
r, err := store.Reader(ctx, m.Digest)
if err != nil {
return err
}
data, err := ioutil.ReadAll(r)
r.Close()
data, err := content.ReadBlob(ctx, store, m.Digest)
if err != nil {
return err
}
@ -111,11 +105,13 @@ func WithTaskCheckpoint(desc v1.Descriptor) NewTaskOpts {
func decodeIndex(ctx context.Context, store content.Store, id digest.Digest) (*v1.Index, error) {
var index v1.Index
r, err := store.Reader(ctx, id)
p, err := content.ReadBlob(ctx, store, id)
if err != nil {
return nil, err
}
err = json.NewDecoder(r).Decode(&index)
r.Close()
return &index, err
if err := json.Unmarshal(p, &index); err != nil {
return nil, err
}
return &index, nil
}

9
content/content.go
View File

@ -9,9 +9,14 @@ import (
"github.com/opencontainers/go-digest"
)
type ReaderAt interface {
io.ReaderAt
io.Closer
Size() int64
}
type Provider interface {
Reader(ctx context.Context, dgst digest.Digest) (io.ReadCloser, error)
ReaderAt(ctx context.Context, dgst digest.Digest) (io.ReaderAt, error)
ReaderAt(ctx context.Context, dgst digest.Digest) (ReaderAt, error)
}
type Ingester interface {

15
content/helpers.go
View File

@ -4,7 +4,6 @@ import (
"context"
"fmt"
"io"
"io/ioutil"
"sync"
"github.com/containerd/containerd/errdefs"
@ -20,17 +19,25 @@ var (
}
)
func NewReader(ra ReaderAt) io.Reader {
rd := io.NewSectionReader(ra, 0, ra.Size())
return rd
}
// 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) {
rc, err := provider.Reader(ctx, dgst)
ra, err := provider.ReaderAt(ctx, dgst)
if err != nil {
return nil, err
}
defer rc.Close()
defer ra.Close()
return ioutil.ReadAll(rc)
p := make([]byte, ra.Size())
_, err = ra.ReadAt(p, 0)
return p, err
}
// WriteBlob writes data with the expected digest into the content store. If

28
content/local/readerat.go
View File

@ -1,26 +1,24 @@
package local
import (
"io"
"os"
)
// readerat implements io.ReaderAt in a completely stateless manner by opening
// the referenced file for each call to ReadAt.
type readerAt struct {
f string
type sizeReaderAt struct {
size int64
fp *os.File
}
func (ra readerAt) ReadAt(p []byte, offset int64) (int, error) {
fp, err := os.Open(ra.f)
if err != nil {
return 0, err
}
defer fp.Close()
if _, err := fp.Seek(offset, io.SeekStart); err != nil {
return 0, err
}
return fp.Read(p)
func (ra sizeReaderAt) ReadAt(p []byte, offset int64) (int, error) {
return ra.fp.ReadAt(p, offset)
}
func (ra sizeReaderAt) Size() int64 {
return ra.size
}
func (ra sizeReaderAt) Close() error {
return ra.fp.Close()
}

28
content/local/store.go
View File

@ -69,22 +69,28 @@ func (s *store) info(dgst digest.Digest, fi os.FileInfo) content.Info {
}
}
// Reader returns an io.ReadCloser for the blob.
func (s *store) Reader(ctx context.Context, dgst digest.Digest) (io.ReadCloser, error) {
fp, err := os.Open(s.blobPath(dgst))
// ReaderAt returns an io.ReaderAt for the blob.
func (s *store) ReaderAt(ctx context.Context, dgst digest.Digest) (content.ReaderAt, error) {
p := s.blobPath(dgst)
fi, err := os.Stat(p)
if err != nil {
if os.IsNotExist(err) {
err = errors.Wrapf(errdefs.ErrNotFound, "content %v", dgst)
if !os.IsNotExist(err) {
return nil, err
}
return nil, err
return nil, errors.Wrapf(errdefs.ErrNotFound, "blob %s expected at %s", dgst, p)
}
return fp, nil
}
fp, err := os.Open(p)
if err != nil {
if !os.IsNotExist(err) {
return nil, err
}
// ReaderAt returns an io.ReaderAt for the blob.
func (s *store) ReaderAt(ctx context.Context, dgst digest.Digest) (io.ReaderAt, error) {
return readerAt{f: s.blobPath(dgst)}, nil
return nil, errors.Wrapf(errdefs.ErrNotFound, "blob %s expected at %s", dgst, p)
}
return sizeReaderAt{size: fi.Size(), fp: fp}, nil
}
// Delete removes a blob by its digest.

4
differ/differ.go
View File

@ -67,14 +67,14 @@ func (s *BaseDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []
}
defer mount.Unmount(dir, 0)
r, err := s.store.Reader(ctx, desc.Digest)
r, err := s.store.ReaderAt(ctx, desc.Digest)
if err != nil {
return emptyDesc, errors.Wrap(err, "failed to get reader from content store")
}
defer r.Close()
// TODO: only decompress stream if media type is compressed
ds, err := compression.DecompressStream(r)
ds, err := compression.DecompressStream(content.NewReader(r))
if err != nil {
return emptyDesc, err
}

6
export.go
View File

@ -43,15 +43,17 @@ func (c *Client) exportToOCITar(ctx context.Context, desc ocispec.Descriptor, wr
func exportHandler(cs content.Store, img oci.ImageDriver) images.HandlerFunc {
return func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
r, err := cs.Reader(ctx, desc.Digest)
r, err := cs.ReaderAt(ctx, desc.Digest)
if err != nil {
return nil, err
}
defer r.Close()
w, err := oci.NewBlobWriter(img, desc.Digest.Algorithm())
if err != nil {
return nil, err
}
if _, err = io.Copy(w, r); err != nil {
if _, err = io.Copy(w, content.NewReader(r)); err != nil {
return nil, err
}
if err = w.Commit(desc.Size, desc.Digest); err != nil {

9
images/image.go
View File

@ -3,7 +3,6 @@ package images
import (
"context"
"encoding/json"
"io/ioutil"
"time"
"github.com/containerd/containerd/content"
@ -73,13 +72,7 @@ func Config(ctx context.Context, provider content.Provider, image ocispec.Descri
return configDesc, Walk(ctx, HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
switch image.MediaType {
case MediaTypeDockerSchema2Manifest, ocispec.MediaTypeImageManifest:
rc, err := provider.Reader(ctx, image.Digest)
if err != nil {
return nil, err
}
defer rc.Close()
p, err := ioutil.ReadAll(rc)
p, err := content.ReadBlob(ctx, provider, image.Digest)
if err != nil {
return nil, err
}

10
metadata/content.go
View File

@ -3,7 +3,6 @@ package metadata
import (
"context"
"encoding/binary"
"io"
"strings"
"time"
@ -421,14 +420,7 @@ func (nw *namespacedWriter) Status() (content.Status, error) {
return st, err
}
func (cs *contentStore) Reader(ctx context.Context, dgst digest.Digest) (io.ReadCloser, error) {
if err := cs.checkAccess(ctx, dgst); err != nil {
return nil, err
}
return cs.Store.Reader(ctx, dgst)
}
func (cs *contentStore) ReaderAt(ctx context.Context, dgst digest.Digest) (io.ReaderAt, error) {
func (cs *contentStore) ReaderAt(ctx context.Context, dgst digest.Digest) (content.ReaderAt, error) {
if err := cs.checkAccess(ctx, dgst); err != nil {
return nil, err
}

6
remotes/docker/schema1/converter.go
View File

@ -210,13 +210,13 @@ 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
r, err := c.contentStore.Reader(ctx, desc.Digest)
ra, err := c.contentStore.ReaderAt(ctx, desc.Digest)
if err != nil {
return err
}
defer r.Close()
defer ra.Close()
gr, err := gzip.NewReader(r)
gr, err := gzip.NewReader(content.NewReader(ra))
if err != nil {
return err
}

8
remotes/handlers.go
View File

@ -3,6 +3,7 @@ package remotes
import (
"context"
"fmt"
"io"
"time"
"github.com/containerd/containerd/content"
@ -131,11 +132,12 @@ func push(ctx context.Context, provider content.Provider, pusher Pusher, desc oc
}
defer cw.Close()
rc, err := provider.Reader(ctx, desc.Digest)
ra, err := provider.ReaderAt(ctx, desc.Digest)
if err != nil {
return err
}
defer rc.Close()
defer ra.Close()
return content.Copy(cw, rc, desc.Size, desc.Digest)
rd := io.NewSectionReader(ra, 0, desc.Size)
return content.Copy(cw, rd, desc.Size, desc.Digest)
}

51
services/content/reader.go
View File

@ -7,54 +7,17 @@ import (
digest "github.com/opencontainers/go-digest"
)
type remoteReader struct {
client contentapi.Content_ReadClient
extra []byte
}
func (rr *remoteReader) Read(p []byte) (n int, err error) {
n += copy(p, rr.extra)
if n >= len(p) {
if n <= len(rr.extra) {
rr.extra = rr.extra[n:]
} else {
rr.extra = rr.extra[:0]
}
return
}
rr.extra = rr.extra[:0]
p = p[n:]
for len(p) > 0 {
var resp *contentapi.ReadContentResponse
// fill our buffer up until we can fill p.
resp, err = rr.client.Recv()
if err != nil {
return
}
copied := copy(p, resp.Data)
n += copied
p = p[copied:]
if len(p) == 0 {
rr.extra = append(rr.extra, resp.Data[copied:]...)
}
}
return
}
func (rr *remoteReader) Close() error {
return rr.client.CloseSend()
}
type remoteReaderAt struct {
ctx context.Context
digest digest.Digest
size int64
client contentapi.ContentClient
}
func (ra *remoteReaderAt) Size() int64 {
return ra.size
}
func (ra *remoteReaderAt) ReadAt(p []byte, off int64) (n int, err error) {
rr := &contentapi.ReadContentRequest{
Digest: ra.digest,
@ -80,3 +43,7 @@ func (ra *remoteReaderAt) ReadAt(p []byte, off int64) (n int, err error) {
}
return n, nil
}
func (rr *remoteReaderAt) Close() error {
return nil
}

13
services/content/service.go
View File

@ -168,20 +168,11 @@ func (s *Service) Read(req *api.ReadContentRequest, session api.Content_ReadServ
return errdefs.ToGRPC(err)
}
rc, err := s.store.Reader(session.Context(), req.Digest)
ra, err := s.store.ReaderAt(session.Context(), req.Digest)
if err != nil {
return errdefs.ToGRPC(err)
}
defer rc.Close() // TODO(stevvooe): Cache these file descriptors for performance.
ra, ok := rc.(io.ReaderAt)
if !ok {
// TODO(stevvooe): Need to set this up to get correct behavior across
// board. May change interface to store to just return ReaderAtCloser.
// Possibly, we could just return io.ReaderAt and handle file
// descriptors internally.
return errors.New("content service only supports content stores that return ReaderAt")
}
defer ra.Close()
var (
offset = req.Offset

11
services/content/store.go
View File

@ -70,21 +70,16 @@ func (rs *remoteStore) Delete(ctx context.Context, dgst digest.Digest) error {
return nil
}
func (rs *remoteStore) Reader(ctx context.Context, dgst digest.Digest) (io.ReadCloser, error) {
client, err := rs.client.Read(ctx, &contentapi.ReadContentRequest{Digest: dgst})
func (rs *remoteStore) ReaderAt(ctx context.Context, dgst digest.Digest) (content.ReaderAt, error) {
i, err := rs.Info(ctx, dgst)
if err != nil {
return nil, err
}
return &remoteReader{
client: client,
}, nil
}
func (rs *remoteStore) ReaderAt(ctx context.Context, dgst digest.Digest) (io.ReaderAt, error) {
return &remoteReaderAt{
ctx: ctx,
digest: dgst,
size: i.Size,
client: rs.client,
}, nil
}

4
services/tasks/service.go
View File

@ -100,11 +100,11 @@ func (s *Service) Create(ctx context.Context, r *api.CreateTaskRequest) (*api.Cr
if r.Checkpoint.MediaType != images.MediaTypeContainerd1Checkpoint {
return nil, fmt.Errorf("unsupported checkpoint type %q", r.Checkpoint.MediaType)
}
reader, err := s.store.Reader(ctx, r.Checkpoint.Digest)
reader, err := s.store.ReaderAt(ctx, r.Checkpoint.Digest)
if err != nil {
return nil, err
}
_, err = archive.Apply(ctx, checkpointPath, reader)
_, err = archive.Apply(ctx, checkpointPath, content.NewReader(reader))
reader.Close()
if err != nil {
return nil, err

8
spec_opts_unix.go
View File

@ -10,6 +10,7 @@ import (
"strings"
"github.com/containerd/containerd/containers"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/typeurl"
"github.com/opencontainers/image-spec/identity"
@ -73,15 +74,14 @@ func WithImageConfig(ctx context.Context, i Image) SpecOpts {
)
switch ic.MediaType {
case v1.MediaTypeImageConfig, images.MediaTypeDockerSchema2Config:
r, err := store.Reader(ctx, ic.Digest)
p, err := content.ReadBlob(ctx, store, ic.Digest)
if err != nil {
return err
}
if err := json.NewDecoder(r).Decode(&ociimage); err != nil {
r.Close()
if err := json.Unmarshal(p, &ociimage); err != nil {
return err
}
r.Close()
config = ociimage.Config
default:
return fmt.Errorf("unknown image config media type %s", ic.MediaType)

7
spec_opts_windows.go
View File

@ -8,6 +8,7 @@ import (
"fmt"
"github.com/containerd/containerd/containers"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/typeurl"
"github.com/opencontainers/image-spec/specs-go/v1"
@ -30,15 +31,13 @@ func WithImageConfig(ctx context.Context, i Image) SpecOpts {
)
switch ic.MediaType {
case v1.MediaTypeImageConfig, images.MediaTypeDockerSchema2Config:
r, err := store.Reader(ctx, ic.Digest)
p, err := content.ReadBlob(ctx, store, ic.Digest)
if err != nil {
return err
}
if err := json.NewDecoder(r).Decode(&ociimage); err != nil {
r.Close()
if err := json.Unmarshal(p, &ociimage); err != nil {
return err
}
r.Close()
config = ociimage.Config
default:
return fmt.Errorf("unknown image config media type %s", ic.MediaType)