Golang ioutils.NewCancelReadCloser函数代码示例

func (pd *v2PushDescriptor) uploadUsingSession(
	ctx context.Context,
	progressOutput progress.Output,
	diffID layer.DiffID,
	layerUpload distribution.BlobWriter,
) (distribution.Descriptor, error) {
	arch, err := pd.layer.TarStream()
	if err != nil {
		return distribution.Descriptor{}, xfer.DoNotRetry{Err: err}
	}

	// don't care if this fails; best effort
	size, _ := pd.layer.DiffSize()

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, arch), progressOutput, size, pd.ID(), "Pushing")
	compressedReader, compressionDone := compress(reader)
	defer func() {
		reader.Close()
		<-compressionDone
	}()

	digester := digest.Canonical.New()
	tee := io.TeeReader(compressedReader, digester.Hash())

	nn, err := layerUpload.ReadFrom(tee)
	compressedReader.Close()
	if err != nil {
		return distribution.Descriptor{}, retryOnError(err)
	}

	pushDigest := digester.Digest()
	if _, err := layerUpload.Commit(ctx, distribution.Descriptor{Digest: pushDigest}); err != nil {
		return distribution.Descriptor{}, retryOnError(err)
	}

	logrus.Debugf("uploaded layer %s (%s), %d bytes", diffID, pushDigest, nn)
	progress.Update(progressOutput, pd.ID(), "Pushed")

	// Cache mapping from this layer's DiffID to the blobsum
	if err := pd.v2MetadataService.TagAndAdd(diffID, pd.hmacKey, metadata.V2Metadata{
		Digest:           pushDigest,
		SourceRepository: pd.repoInfo.FullName(),
	}); err != nil {
		return distribution.Descriptor{}, xfer.DoNotRetry{Err: err}
	}

	desc := distribution.Descriptor{
		Digest:    pushDigest,
		MediaType: schema2.MediaTypeLayer,
		Size:      nn,
	}

	pd.pushState.Lock()
	// If Commit succeeded, that's an indication that the remote registry speaks the v2 protocol.
	pd.pushState.confirmedV2 = true
	pd.pushState.remoteLayers[diffID] = desc
	pd.pushState.Unlock()

	return desc, nil
}

// fetch fetches the given URL using ctxhttp. It also streams back the progress bar only when ID is not an empty string.
func (u *URLFetcher) fetchToFile(ctx context.Context, url *url.URL, ID string, po progress.Output) (string, error) {
	rdr, hdrs, err := u.fetch(ctx, url, ID)
	if err != nil {
		return "", err
	}
	defer rdr.Close()

	// stream progress as json and body into a file - only if we have an ID and a Content-Length header
	if contLen := hdrs.Get("Content-Length"); ID != "" && contLen != "" {
		cl, cerr := strconv.ParseInt(contLen, 10, 64)
		if cerr != nil {
			return "", cerr
		}

		if po != nil {
			rdr = progress.NewProgressReader(
				ioutils.NewCancelReadCloser(ctx, rdr), po, cl, ID, "Downloading",
			)
			defer rdr.Close()
		} else {
			rdr = ioutils.NewCancelReadCloser(ctx, rdr)
		}
	}

	// Create a temporary file and stream the res.Body into it
	out, err := ioutil.TempFile(os.TempDir(), ID)
	if err != nil {
		return "", DoNotRetry{Err: err}
	}
	defer out.Close()

	// Stream into it
	_, err = io.Copy(out, rdr)
	if err != nil {
		log.Errorf("Fetch (%s) to file failed to stream to file: %s", url.String(), err)

		// cleanup
		defer os.Remove(out.Name())
		return "", DoNotRetry{Err: err}
	}

	// Return the temporary file name
	return out.Name(), nil
}

func (p *v1Pusher) pushImage(ctx context.Context, v1Image v1Image, ep string) (checksum string, err error) {
	l := v1Image.Layer()
	v1ID := v1Image.V1ID()
	truncID := stringid.TruncateID(l.DiffID().String())

	jsonRaw := v1Image.Config()
	progress.Update(p.config.ProgressOutput, truncID, "Pushing")

	// General rule is to use ID for graph accesses and compatibilityID for
	// calls to session.registry()
	imgData := &registry.ImgData{
		ID: v1ID,
	}

	// Send the json
	if err := p.session.PushImageJSONRegistry(imgData, jsonRaw, ep); err != nil {
		if err == registry.ErrAlreadyExists {
			progress.Update(p.config.ProgressOutput, truncID, "Image already pushed, skipping")
			return "", nil
		}
		return "", err
	}

	arch, err := l.TarStream()
	if err != nil {
		return "", err
	}
	defer arch.Close()

	// don't care if this fails; best effort
	size, _ := l.DiffSize()

	// Send the layer
	logrus.Debugf("rendered layer for %s of [%d] size", v1ID, size)

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, arch), p.config.ProgressOutput, size, truncID, "Pushing")
	defer reader.Close()

	checksum, checksumPayload, err := p.session.PushImageLayerRegistry(v1ID, reader, ep, jsonRaw)
	if err != nil {
		return "", err
	}
	imgData.Checksum = checksum
	imgData.ChecksumPayload = checksumPayload
	// Send the checksum
	if err := p.session.PushImageChecksumRegistry(imgData, ep); err != nil {
		return "", err
	}

	if err := p.v1IDService.Set(v1ID, p.repoInfo.Index.Name, l.DiffID()); err != nil {
		logrus.Warnf("Could not set v1 ID mapping: %v", err)
	}

	progress.Update(p.config.ProgressOutput, truncID, "Image successfully pushed")
	return imgData.Checksum, nil
}

func (ld *v1LayerDescriptor) Download(ctx context.Context, progressOutput progress.Output) (io.ReadCloser, int64, error) {
	progress.Update(progressOutput, ld.ID(), "Pulling fs layer")
	layerReader, err := ld.session.GetRemoteImageLayer(ld.v1LayerID, ld.endpoint, ld.layerSize)
	if err != nil {
		progress.Update(progressOutput, ld.ID(), "Error pulling dependent layers")
		if uerr, ok := err.(*url.Error); ok {
			err = uerr.Err
		}
		if terr, ok := err.(net.Error); ok && terr.Timeout() {
			return nil, 0, err
		}
		return nil, 0, xfer.DoNotRetry{Err: err}
	}
	*ld.layersDownloaded = true

	ld.tmpFile, err = ioutil.TempFile("", "GetImageBlob")
	if err != nil {
		layerReader.Close()
		return nil, 0, err
	}

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, layerReader), progressOutput, ld.layerSize, ld.ID(), "Downloading")
	defer reader.Close()

	_, err = io.Copy(ld.tmpFile, reader)
	if err != nil {
		ld.Close()
		return nil, 0, err
	}

	progress.Update(progressOutput, ld.ID(), "Download complete")

	logrus.Debugf("Downloaded %s to tempfile %s", ld.ID(), ld.tmpFile.Name())

	ld.tmpFile.Seek(0, 0)

	// hand off the temporary file to the download manager, so it will only
	// be closed once
	tmpFile := ld.tmpFile
	ld.tmpFile = nil

	return ioutils.NewReadCloserWrapper(tmpFile, func() error {
		tmpFile.Close()
		err := os.RemoveAll(tmpFile.Name())
		if err != nil {
			logrus.Errorf("Failed to remove temp file: %s", tmpFile.Name())
		}
		return err
	}), ld.layerSize, nil
}

// WriteImageBlobs writes the image blob to the storage layer
func WriteImageBlobs(images []*ImageWithMeta) error {
	if options.standalone {
		return nil
	}

	// iterate from parent to children
	// so that portlayer can extract each layer
	// on top of previous one
	destination := DestinationDirectory()
	for i := len(images) - 1; i >= 0; i-- {
		image := images[i]

		id := image.Image.ID
		f, err := os.Open(path.Join(destination, id, id+".tar"))
		if err != nil {
			return fmt.Errorf("Failed to open file: %s", err)
		}
		defer f.Close()

		fi, err := f.Stat()
		if err != nil {
			return fmt.Errorf("Failed to stat file: %s", err)
		}

		in := progress.NewProgressReader(
			ioutils.NewCancelReadCloser(context.Background(), f),
			po,
			fi.Size(),
			image.String(),
			"Extracting",
		)
		defer in.Close()

		// Write the image
		err = WriteImage(image, in)
		if err != nil {
			return fmt.Errorf("Failed to write to image store: %s", err)
		}
		progress.Update(po, image.String(), "Pull complete")
	}
	if err := os.RemoveAll(destination); err != nil {
		return fmt.Errorf("Failed to remove download directory: %s", err)
	}
	return nil
}

// WriteImageBlob writes the image blob to the storage layer
func (ic *ImageC) WriteImageBlob(image *ImageWithMeta, progressOutput progress.Output, cleanup bool) error {
	defer trace.End(trace.Begin(image.Image.ID))

	destination := DestinationDirectory(ic.Options)

	id := image.Image.ID
	log.Infof("Path: %s", path.Join(destination, id, id+".targ"))
	f, err := os.Open(path.Join(destination, id, id+".tar"))
	if err != nil {
		return fmt.Errorf("Failed to open file: %s", err)
	}
	defer f.Close()

	fi, err := f.Stat()
	if err != nil {
		return fmt.Errorf("Failed to stat file: %s", err)
	}

	in := progress.NewProgressReader(
		ioutils.NewCancelReadCloser(context.Background(), f),
		progressOutput,
		fi.Size(),
		image.String(),
		"Extracting",
	)
	defer in.Close()

	// Write the image
	err = WriteImage(ic.Host, image, in)
	if err != nil {
		return fmt.Errorf("Failed to write to image store: %s", err)
	}

	progress.Update(progressOutput, image.String(), "Pull complete")

	if cleanup {
		if err := os.RemoveAll(destination); err != nil {
			return fmt.Errorf("Failed to remove download directory: %s", err)
		}
	}
	return nil
}

func (ld *v1LayerDescriptor) Download(ctx context.Context, progressOutput progress.Output) (io.ReadCloser, int64, error) {
	progress.Update(progressOutput, ld.ID(), "Pulling fs layer")
	layerReader, err := ld.session.GetRemoteImageLayer(ld.v1LayerID, ld.endpoint, ld.layerSize)
	if err != nil {
		progress.Update(progressOutput, ld.ID(), "Error pulling dependent layers")
		if uerr, ok := err.(*url.Error); ok {
			err = uerr.Err
		}
		if terr, ok := err.(net.Error); ok && terr.Timeout() {
			return nil, 0, err
		}
		return nil, 0, xfer.DoNotRetry{Err: err}
	}
	*ld.layersDownloaded = true

	ld.tmpFile, err = ioutil.TempFile("", "GetImageBlob")
	if err != nil {
		layerReader.Close()
		return nil, 0, err
	}

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, layerReader), progressOutput, ld.layerSize, ld.ID(), "Downloading")
	defer reader.Close()

	_, err = io.Copy(ld.tmpFile, reader)
	if err != nil {
		ld.Close()
		return nil, 0, err
	}

	progress.Update(progressOutput, ld.ID(), "Download complete")

	logrus.Debugf("Downloaded %s to tempfile %s", ld.ID(), ld.tmpFile.Name())

	ld.tmpFile.Seek(0, 0)
	return ld.tmpFile, ld.layerSize, nil
}

//.........这里部分代码省略.........
				default:
				}

				retries++
				if _, isDNR := err.(DoNotRetry); isDNR || retries == maxDownloadAttempts {
					logrus.Errorf("Download failed: %v", err)
					d.err = err
					return
				}

				logrus.Errorf("Download failed, retrying: %v", err)
				delay := retries * 5
				ticker := time.NewTicker(time.Second)

			selectLoop:
				for {
					progress.Updatef(progressOutput, descriptor.ID(), "Retrying in %d second%s", delay, (map[bool]string{true: "s"})[delay != 1])
					select {
					case <-ticker.C:
						delay--
						if delay == 0 {
							ticker.Stop()
							break selectLoop
						}
					case <-d.Transfer.Context().Done():
						ticker.Stop()
						d.err = errors.New("download cancelled during retry delay")
						return
					}

				}
			}

			close(inactive)

			if parentDownload != nil {
				select {
				case <-d.Transfer.Context().Done():
					d.err = errors.New("layer registration cancelled")
					downloadReader.Close()
					return
				case <-parentDownload.Done():
				}

				l, err := parentDownload.result()
				if err != nil {
					d.err = err
					downloadReader.Close()
					return
				}
				parentLayer = l.ChainID()
			}

			reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(d.Transfer.Context(), downloadReader), progressOutput, size, descriptor.ID(), "Extracting")
			defer reader.Close()

			inflatedLayerData, err := archive.DecompressStream(reader)
			if err != nil {
				d.err = fmt.Errorf("could not get decompression stream: %v", err)
				return
			}

			var src distribution.Descriptor
			if fs, ok := descriptor.(distribution.Describable); ok {
				src = fs.Descriptor()
			}
			if ds, ok := d.layerStore.(layer.DescribableStore); ok {
				d.layer, err = ds.RegisterWithDescriptor(inflatedLayerData, parentLayer, src)
			} else {
				d.layer, err = d.layerStore.Register(inflatedLayerData, parentLayer)
			}
			if err != nil {
				select {
				case <-d.Transfer.Context().Done():
					d.err = errors.New("layer registration cancelled")
				default:
					d.err = fmt.Errorf("failed to register layer: %v", err)
				}
				return
			}

			progress.Update(progressOutput, descriptor.ID(), "Pull complete")
			withRegistered, hasRegistered := descriptor.(DownloadDescriptorWithRegistered)
			if hasRegistered {
				withRegistered.Registered(d.layer.DiffID())
			}

			// Doesn't actually need to be its own goroutine, but
			// done like this so we can defer close(c).
			go func() {
				<-d.Transfer.Released()
				if d.layer != nil {
					layer.ReleaseAndLog(d.layerStore, d.layer)
				}
			}()
		}()

		return d
	}
}

func (ld *v2LayerDescriptor) Download(ctx context.Context, progressOutput progress.Output) (io.ReadCloser, int64, error) {
	logrus.Debugf("pulling blob %q", ld.digest)

	blobs := ld.repo.Blobs(ctx)

	layerDownload, err := blobs.Open(ctx, ld.digest)
	if err != nil {
		logrus.Debugf("Error statting layer: %v", err)
		if err == distribution.ErrBlobUnknown {
			return nil, 0, xfer.DoNotRetry{Err: err}
		}
		return nil, 0, retryOnError(err)
	}

	size, err := layerDownload.Seek(0, os.SEEK_END)
	if err != nil {
		// Seek failed, perhaps because there was no Content-Length
		// header. This shouldn't fail the download, because we can
		// still continue without a progress bar.
		size = 0
	} else {
		// Restore the seek offset at the beginning of the stream.
		_, err = layerDownload.Seek(0, os.SEEK_SET)
		if err != nil {
			return nil, 0, err
		}
	}

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, layerDownload), progressOutput, size, ld.ID(), "Downloading")
	defer reader.Close()

	verifier, err := digest.NewDigestVerifier(ld.digest)
	if err != nil {
		return nil, 0, xfer.DoNotRetry{Err: err}
	}

	tmpFile, err := ioutil.TempFile("", "GetImageBlob")
	if err != nil {
		return nil, 0, xfer.DoNotRetry{Err: err}
	}

	_, err = io.Copy(tmpFile, io.TeeReader(reader, verifier))
	if err != nil {
		return nil, 0, retryOnError(err)
	}

	progress.Update(progressOutput, ld.ID(), "Verifying Checksum")

	if !verifier.Verified() {
		err = fmt.Errorf("filesystem layer verification failed for digest %s", ld.digest)
		logrus.Error(err)
		tmpFile.Close()
		if err := os.RemoveAll(tmpFile.Name()); err != nil {
			logrus.Errorf("Failed to remove temp file: %s", tmpFile.Name())
		}

		return nil, 0, xfer.DoNotRetry{Err: err}
	}

	progress.Update(progressOutput, ld.ID(), "Download complete")

	logrus.Debugf("Downloaded %s to tempfile %s", ld.ID(), tmpFile.Name())

	tmpFile.Seek(0, 0)
	return ioutils.NewReadCloserWrapper(tmpFile, tmpFileCloser(tmpFile)), size, nil
}

//.........这里部分代码省略.........
		// TODO (brianbland): We need to construct a reference where the Name is
		// only the full remote name, so clean this up when distribution has a
		// richer reference package
		remoteRef, err := distreference.WithName(namedRef.RemoteName())
		if err != nil {
			return err
		}

		canonicalRef, err := distreference.WithDigest(remoteRef, mountFrom.Digest)
		if err != nil {
			return err
		}

		createOpts = append(createOpts, client.WithMountFrom(canonicalRef))
	}

	// Send the layer
	layerUpload, err := bs.Create(ctx, createOpts...)
	switch err := err.(type) {
	case distribution.ErrBlobMounted:
		progress.Updatef(progressOutput, pd.ID(), "Mounted from %s", err.From.Name())

		err.Descriptor.MediaType = schema2.MediaTypeLayer

		pd.pushState.Lock()
		pd.pushState.confirmedV2 = true
		pd.pushState.remoteLayers[diffID] = err.Descriptor
		pd.pushState.Unlock()

		// Cache mapping from this layer's DiffID to the blobsum
		if err := pd.v2MetadataService.Add(diffID, metadata.V2Metadata{Digest: mountFrom.Digest, SourceRepository: pd.repoInfo.FullName()}); err != nil {
			return xfer.DoNotRetry{Err: err}
		}

		return nil
	}
	if mountFrom.SourceRepository != "" {
		// unable to mount layer from this repository, so this source mapping is no longer valid
		logrus.Debugf("unassociating layer %s (%s) with %s", diffID, mountFrom.Digest, mountFrom.SourceRepository)
		pd.v2MetadataService.Remove(mountFrom)
	}

	if err != nil {
		return retryOnError(err)
	}
	defer layerUpload.Close()

	arch, err := pd.layer.TarStream()
	if err != nil {
		return xfer.DoNotRetry{Err: err}
	}

	// don't care if this fails; best effort
	size, _ := pd.layer.DiffSize()

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, arch), progressOutput, size, pd.ID(), "Pushing")
	compressedReader, compressionDone := compress(reader)
	defer func() {
		reader.Close()
		<-compressionDone
	}()

	digester := digest.Canonical.New()
	tee := io.TeeReader(compressedReader, digester.Hash())

	nn, err := layerUpload.ReadFrom(tee)
	compressedReader.Close()
	if err != nil {
		return retryOnError(err)
	}

	pushDigest := digester.Digest()
	if _, err := layerUpload.Commit(ctx, distribution.Descriptor{Digest: pushDigest}); err != nil {
		return retryOnError(err)
	}

	logrus.Debugf("uploaded layer %s (%s), %d bytes", diffID, pushDigest, nn)
	progress.Update(progressOutput, pd.ID(), "Pushed")

	// Cache mapping from this layer's DiffID to the blobsum
	if err := pd.v2MetadataService.Add(diffID, metadata.V2Metadata{Digest: pushDigest, SourceRepository: pd.repoInfo.FullName()}); err != nil {
		return xfer.DoNotRetry{Err: err}
	}

	pd.pushState.Lock()

	// If Commit succeded, that's an indication that the remote registry
	// speaks the v2 protocol.
	pd.pushState.confirmedV2 = true

	pd.pushState.remoteLayers[diffID] = distribution.Descriptor{
		Digest:    pushDigest,
		MediaType: schema2.MediaTypeLayer,
		Size:      nn,
	}

	pd.pushState.Unlock()

	return nil
}

// fetch fetches the given URL using ctxhttp. It also streams back the progress bar only when ID is not an empty string.
func (u *URLFetcher) fetch(ctx context.Context, url *url.URL, ID string) (string, error) {
	req, err := http.NewRequest("GET", url.String(), nil)
	if err != nil {
		return "", err
	}

	u.setBasicAuth(req)

	u.setAuthToken(req)

	res, err := ctxhttp.Do(ctx, u.client, req)
	if err != nil {
		return "", err
	}
	defer res.Body.Close()

	u.StatusCode = res.StatusCode

	if u.options.Token == nil && u.IsStatusUnauthorized() {
		hdr := res.Header.Get("www-authenticate")
		if hdr == "" {
			return "", fmt.Errorf("www-authenticate header is missing")
		}
		u.OAuthEndpoint, err = u.extractQueryParams(hdr, url)
		if err != nil {
			return "", err
		}
		return "", DoNotRetry{Err: fmt.Errorf("Authentication required")}
	}

	if u.IsStatusNotFound() {
		return "", fmt.Errorf("Not found: %d, URL: %s", u.StatusCode, url)
	}

	if u.IsStatusUnauthorized() {
		hdr := res.Header.Get("www-authenticate")

		// check if image is non-existent (#757)
		if strings.Contains(hdr, "error=\"insufficient_scope\"") {
			return "", DoNotRetry{Err: fmt.Errorf("image not found")}
		} else if strings.Contains(hdr, "error=\"invalid_token\"") {
			return "", fmt.Errorf("not authorized")
		} else {
			return "", fmt.Errorf("Unexpected http code: %d, URL: %s", u.StatusCode, url)
		}
	}

	// FIXME: handle StatusTemporaryRedirect and StatusFound
	if !u.IsStatusOK() {
		return "", fmt.Errorf("Unexpected http code: %d, URL: %s", u.StatusCode, url)
	}

	in := res.Body
	// stream progress as json and body into a file - only if we have an ID and a Content-Length header
	if hdr := res.Header.Get("Content-Length"); ID != "" && hdr != "" {
		cl, cerr := strconv.ParseInt(hdr, 10, 64)
		if cerr != nil {
			return "", cerr
		}

		in = progress.NewProgressReader(
			ioutils.NewCancelReadCloser(ctx, res.Body), po, cl, ID, "Downloading",
		)
		defer in.Close()
	}

	// Create a temporary file and stream the res.Body into it
	out, err := ioutil.TempFile(os.TempDir(), ID)
	if err != nil {
		return "", DoNotRetry{Err: err}
	}
	defer out.Close()

	// Stream into it
	_, err = io.Copy(out, in)
	if err != nil {
		// cleanup
		defer os.Remove(out.Name())
		return "", DoNotRetry{Err: err}
	}

	// Return the temporary file name
	return out.Name(), nil
}

func (ld *v2LayerDescriptor) Download(ctx context.Context, progressOutput progress.Output) (io.ReadCloser, int64, error) {
	logrus.Debugf("pulling blob %q", ld.digest)

	var (
		err    error
		offset int64
	)

	if ld.tmpFile == nil {
		ld.tmpFile, err = createDownloadFile()
		if err != nil {
			return nil, 0, xfer.DoNotRetry{Err: err}
		}
	} else {
		offset, err = ld.tmpFile.Seek(0, os.SEEK_END)
		if err != nil {
			logrus.Debugf("error seeking to end of download file: %v", err)
			offset = 0

			ld.tmpFile.Close()
			if err := os.Remove(ld.tmpFile.Name()); err != nil {
				logrus.Errorf("Failed to remove temp file: %s", ld.tmpFile.Name())
			}
			ld.tmpFile, err = createDownloadFile()
			if err != nil {
				return nil, 0, xfer.DoNotRetry{Err: err}
			}
		} else if offset != 0 {
			logrus.Debugf("attempting to resume download of %q from %d bytes", ld.digest, offset)
		}
	}

	tmpFile := ld.tmpFile

	layerDownload, err := ld.open(ctx)
	if err != nil {
		logrus.Errorf("Error initiating layer download: %v", err)
		if err == distribution.ErrBlobUnknown {
			return nil, 0, xfer.DoNotRetry{Err: err}
		}
		return nil, 0, retryOnError(err)
	}

	if offset != 0 {
		_, err := layerDownload.Seek(offset, os.SEEK_SET)
		if err != nil {
			if err := ld.truncateDownloadFile(); err != nil {
				return nil, 0, xfer.DoNotRetry{Err: err}
			}
			return nil, 0, err
		}
	}
	size, err := layerDownload.Seek(0, os.SEEK_END)
	if err != nil {
		// Seek failed, perhaps because there was no Content-Length
		// header. This shouldn't fail the download, because we can
		// still continue without a progress bar.
		size = 0
	} else {
		if size != 0 && offset > size {
			logrus.Debug("Partial download is larger than full blob. Starting over")
			offset = 0
			if err := ld.truncateDownloadFile(); err != nil {
				return nil, 0, xfer.DoNotRetry{Err: err}
			}
		}

		// Restore the seek offset either at the beginning of the
		// stream, or just after the last byte we have from previous
		// attempts.
		_, err = layerDownload.Seek(offset, os.SEEK_SET)
		if err != nil {
			return nil, 0, err
		}
	}

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, layerDownload), progressOutput, size-offset, ld.ID(), "Downloading")
	defer reader.Close()

	if ld.verifier == nil {
		ld.verifier, err = digest.NewDigestVerifier(ld.digest)
		if err != nil {
			return nil, 0, xfer.DoNotRetry{Err: err}
		}
	}

	_, err = io.Copy(tmpFile, io.TeeReader(reader, ld.verifier))
	if err != nil {
		if err == transport.ErrWrongCodeForByteRange {
			if err := ld.truncateDownloadFile(); err != nil {
				return nil, 0, xfer.DoNotRetry{Err: err}
			}
			return nil, 0, err
		}
		return nil, 0, retryOnError(err)
	}

	progress.Update(progressOutput, ld.ID(), "Verifying Checksum")

	if !ld.verifier.Verified() {
//.........这里部分代码省略.........

//.........这里部分代码省略.........
			continue
		}

		canonicalRef, err := distreference.WithDigest(remoteRef, mountFrom.Digest)
		if err != nil {
			continue
		}

		logrus.Debugf("attempting to mount layer %s (%s) from %s", diffID, mountFrom.Digest, sourceRepo.FullName())

		layerUpload, err = bs.Create(ctx, client.WithMountFrom(canonicalRef))
		switch err := err.(type) {
		case distribution.ErrBlobMounted:
			progress.Updatef(progressOutput, pd.ID(), "Mounted from %s", err.From.Name())

			err.Descriptor.MediaType = schema2.MediaTypeLayer

			pd.pushState.Lock()
			pd.pushState.confirmedV2 = true
			pd.pushState.remoteLayers[diffID] = err.Descriptor
			pd.pushState.Unlock()

			// Cache mapping from this layer's DiffID to the blobsum
			if err := pd.v2MetadataService.Add(diffID, metadata.V2Metadata{Digest: mountFrom.Digest, SourceRepository: pd.repoInfo.FullName()}); err != nil {
				return distribution.Descriptor{}, xfer.DoNotRetry{Err: err}
			}
			return err.Descriptor, nil
		case nil:
			// blob upload session created successfully, so begin the upload
			mountAttemptsRemaining = 0
		default:
			// unable to mount layer from this repository, so this source mapping is no longer valid
			logrus.Debugf("unassociating layer %s (%s) with %s", diffID, mountFrom.Digest, mountFrom.SourceRepository)
			pd.v2MetadataService.Remove(mountFrom)
			mountAttemptsRemaining--
		}
	}

	if layerUpload == nil {
		layerUpload, err = bs.Create(ctx)
		if err != nil {
			return distribution.Descriptor{}, retryOnError(err)
		}
	}
	defer layerUpload.Close()

	arch, err := pd.layer.TarStream()
	if err != nil {
		return distribution.Descriptor{}, xfer.DoNotRetry{Err: err}
	}

	// don't care if this fails; best effort
	size, _ := pd.layer.DiffSize()

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, arch), progressOutput, size, pd.ID(), "Pushing")
	compressedReader, compressionDone := compress(reader)
	defer func() {
		reader.Close()
		<-compressionDone
	}()

	digester := digest.Canonical.New()
	tee := io.TeeReader(compressedReader, digester.Hash())

	nn, err := layerUpload.ReadFrom(tee)
	compressedReader.Close()
	if err != nil {
		return distribution.Descriptor{}, retryOnError(err)
	}

	pushDigest := digester.Digest()
	if _, err := layerUpload.Commit(ctx, distribution.Descriptor{Digest: pushDigest}); err != nil {
		return distribution.Descriptor{}, retryOnError(err)
	}

	logrus.Debugf("uploaded layer %s (%s), %d bytes", diffID, pushDigest, nn)
	progress.Update(progressOutput, pd.ID(), "Pushed")

	// Cache mapping from this layer's DiffID to the blobsum
	if err := pd.v2MetadataService.Add(diffID, metadata.V2Metadata{Digest: pushDigest, SourceRepository: pd.repoInfo.FullName()}); err != nil {
		return distribution.Descriptor{}, xfer.DoNotRetry{Err: err}
	}

	pd.pushState.Lock()

	// If Commit succeeded, that's an indication that the remote registry
	// speaks the v2 protocol.
	pd.pushState.confirmedV2 = true

	descriptor := distribution.Descriptor{
		Digest:    pushDigest,
		MediaType: schema2.MediaTypeLayer,
		Size:      nn,
	}
	pd.pushState.remoteLayers[diffID] = descriptor

	pd.pushState.Unlock()

	return descriptor, nil
}

func (pd *v2PushDescriptor) Upload(ctx context.Context, progressOutput progress.Output) (digest.Digest, error) {
	diffID := pd.DiffID()

	logrus.Debugf("Pushing layer: %s", diffID)

	// Do we have any blobsums associated with this layer's DiffID?
	possibleBlobsums, err := pd.blobSumService.GetBlobSums(diffID)
	if err == nil {
		dgst, exists, err := blobSumAlreadyExists(ctx, possibleBlobsums, pd.repo, pd.layersPushed)
		if err != nil {
			progress.Update(progressOutput, pd.ID(), "Image push failed")
			return "", retryOnError(err)
		}
		if exists {
			progress.Update(progressOutput, pd.ID(), "Layer already exists")
			return dgst, nil
		}
	}

	// if digest was empty or not saved, or if blob does not exist on the remote repository,
	// then push the blob.
	bs := pd.repo.Blobs(ctx)

	// Send the layer
	layerUpload, err := bs.Create(ctx)
	if err != nil {
		return "", retryOnError(err)
	}
	defer layerUpload.Close()

	arch, err := pd.layer.TarStream()
	if err != nil {
		return "", xfer.DoNotRetry{Err: err}
	}

	// don't care if this fails; best effort
	size, _ := pd.layer.DiffSize()

	reader := progress.NewProgressReader(ioutils.NewCancelReadCloser(ctx, arch), progressOutput, size, pd.ID(), "Pushing")
	defer reader.Close()
	compressedReader := compress(reader)

	digester := digest.Canonical.New()
	tee := io.TeeReader(compressedReader, digester.Hash())

	nn, err := layerUpload.ReadFrom(tee)
	compressedReader.Close()
	if err != nil {
		return "", retryOnError(err)
	}

	pushDigest := digester.Digest()
	if _, err := layerUpload.Commit(ctx, distribution.Descriptor{Digest: pushDigest}); err != nil {
		return "", retryOnError(err)
	}

	// If Commit succeded, that's an indication that the remote registry
	// speaks the v2 protocol.
	*pd.confirmedV2 = true

	logrus.Debugf("uploaded layer %s (%s), %d bytes", diffID, pushDigest, nn)
	progress.Update(progressOutput, pd.ID(), "Pushed")

	// Cache mapping from this layer's DiffID to the blobsum
	if err := pd.blobSumService.Add(diffID, pushDigest); err != nil {
		return "", xfer.DoNotRetry{Err: err}
	}

	pd.layersPushed.Lock()
	pd.layersPushed.layersPushed[pushDigest] = true
	pd.layersPushed.Unlock()

	return pushDigest, nil
}