Move client package under registry package

Signed-off-by: Stephen J Day <stephen.day@docker.com>

docs/client/client.go

@@ -0,0 +1,574 @@
+package client
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strconv"
+
+	"github.com/docker/distribution/registry/api/v2"
+	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/manifest"
+)
+
+// Client implements the client interface to the registry http api
+type Client interface {
+	// GetImageManifest returns an image manifest for the image at the given
+	// name, tag pair.
+	GetImageManifest(name, tag string) (*manifest.SignedManifest, error)
+
+	// PutImageManifest uploads an image manifest for the image at the given
+	// name, tag pair.
+	PutImageManifest(name, tag string, imageManifest *manifest.SignedManifest) error
+
+	// DeleteImage removes the image at the given name, tag pair.
+	DeleteImage(name, tag string) error
+
+	// ListImageTags returns a list of all image tags with the given repository
+	// name.
+	ListImageTags(name string) ([]string, error)
+
+	// BlobLength returns the length of the blob stored at the given name,
+	// digest pair.
+	// Returns a length value of -1 on error or if the blob does not exist.
+	BlobLength(name string, dgst digest.Digest) (int, error)
+
+	// GetBlob returns the blob stored at the given name, digest pair in the
+	// form of an io.ReadCloser with the length of this blob.
+	// A nonzero byteOffset can be provided to receive a partial blob beginning
+	// at the given offset.
+	GetBlob(name string, dgst digest.Digest, byteOffset int) (io.ReadCloser, int, error)
+
+	// InitiateBlobUpload starts a blob upload in the given repository namespace
+	// and returns a unique location url to use for other blob upload methods.
+	InitiateBlobUpload(name string) (string, error)
+
+	// GetBlobUploadStatus returns the byte offset and length of the blob at the
+	// given upload location.
+	GetBlobUploadStatus(location string) (int, int, error)
+
+	// UploadBlob uploads a full blob to the registry.
+	UploadBlob(location string, blob io.ReadCloser, length int, dgst digest.Digest) error
+
+	// UploadBlobChunk uploads a blob chunk with a given length and startByte to
+	// the registry.
+	// FinishChunkedBlobUpload must be called to finalize this upload.
+	UploadBlobChunk(location string, blobChunk io.ReadCloser, length, startByte int) error
+
+	// FinishChunkedBlobUpload completes a chunked blob upload at a given
+	// location.
+	FinishChunkedBlobUpload(location string, length int, dgst digest.Digest) error
+
+	// CancelBlobUpload deletes all content at the unfinished blob upload
+	// location and invalidates any future calls to this blob upload.
+	CancelBlobUpload(location string) error
+}
+
+var (
+	patternRangeHeader = regexp.MustCompile("bytes=0-(\\d+)/(\\d+)")
+)
+
+// New returns a new Client which operates against a registry with the
+// given base endpoint
+// This endpoint should not include /v2/ or any part of the url after this.
+func New(endpoint string) (Client, error) {
+	ub, err := v2.NewURLBuilderFromString(endpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	return &clientImpl{
+		endpoint: endpoint,
+		ub:       ub,
+	}, nil
+}
+
+// clientImpl is the default implementation of the Client interface
+type clientImpl struct {
+	endpoint string
+	ub       *v2.URLBuilder
+}
+
+// TODO(bbland): use consistent route generation between server and client
+
+func (r *clientImpl) GetImageManifest(name, tag string) (*manifest.SignedManifest, error) {
+	manifestURL, err := r.ub.BuildManifestURL(name, tag)
+	if err != nil {
+		return nil, err
+	}
+
+	response, err := http.Get(manifestURL)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusOK:
+		break
+	case response.StatusCode == http.StatusNotFound:
+		return nil, &ImageManifestNotFoundError{Name: name, Tag: tag}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return nil, err
+		}
+		return nil, &errs
+	default:
+		return nil, &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+
+	decoder := json.NewDecoder(response.Body)
+
+	manifest := new(manifest.SignedManifest)
+	err = decoder.Decode(manifest)
+	if err != nil {
+		return nil, err
+	}
+	return manifest, nil
+}
+
+func (r *clientImpl) PutImageManifest(name, tag string, manifest *manifest.SignedManifest) error {
+	manifestURL, err := r.ub.BuildManifestURL(name, tag)
+	if err != nil {
+		return err
+	}
+
+	putRequest, err := http.NewRequest("PUT", manifestURL, bytes.NewReader(manifest.Raw))
+	if err != nil {
+		return err
+	}
+
+	response, err := http.DefaultClient.Do(putRequest)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusOK || response.StatusCode == http.StatusAccepted:
+		return nil
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errors v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errors)
+		if err != nil {
+			return err
+		}
+
+		return &errors
+	default:
+		return &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) DeleteImage(name, tag string) error {
+	manifestURL, err := r.ub.BuildManifestURL(name, tag)
+	if err != nil {
+		return err
+	}
+
+	deleteRequest, err := http.NewRequest("DELETE", manifestURL, nil)
+	if err != nil {
+		return err
+	}
+
+	response, err := http.DefaultClient.Do(deleteRequest)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusNoContent:
+		break
+	case response.StatusCode == http.StatusNotFound:
+		return &ImageManifestNotFoundError{Name: name, Tag: tag}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return err
+		}
+		return &errs
+	default:
+		return &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+
+	return nil
+}
+
+func (r *clientImpl) ListImageTags(name string) ([]string, error) {
+	tagsURL, err := r.ub.BuildTagsURL(name)
+	if err != nil {
+		return nil, err
+	}
+
+	response, err := http.Get(tagsURL)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusOK:
+		break
+	case response.StatusCode == http.StatusNotFound:
+		return nil, &RepositoryNotFoundError{Name: name}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return nil, err
+		}
+		return nil, &errs
+	default:
+		return nil, &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+
+	tags := struct {
+		Tags []string `json:"tags"`
+	}{}
+
+	decoder := json.NewDecoder(response.Body)
+	err = decoder.Decode(&tags)
+	if err != nil {
+		return nil, err
+	}
+
+	return tags.Tags, nil
+}
+
+func (r *clientImpl) BlobLength(name string, dgst digest.Digest) (int, error) {
+	blobURL, err := r.ub.BuildBlobURL(name, dgst)
+	if err != nil {
+		return -1, err
+	}
+
+	response, err := http.Head(blobURL)
+	if err != nil {
+		return -1, err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusOK:
+		lengthHeader := response.Header.Get("Content-Length")
+		length, err := strconv.ParseInt(lengthHeader, 10, 64)
+		if err != nil {
+			return -1, err
+		}
+		return int(length), nil
+	case response.StatusCode == http.StatusNotFound:
+		return -1, nil
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return -1, err
+		}
+		return -1, &errs
+	default:
+		response.Body.Close()
+		return -1, &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) GetBlob(name string, dgst digest.Digest, byteOffset int) (io.ReadCloser, int, error) {
+	blobURL, err := r.ub.BuildBlobURL(name, dgst)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	getRequest, err := http.NewRequest("GET", blobURL, nil)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	getRequest.Header.Add("Range", fmt.Sprintf("%d-", byteOffset))
+	response, err := http.DefaultClient.Do(getRequest)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusOK:
+		lengthHeader := response.Header.Get("Content-Length")
+		length, err := strconv.ParseInt(lengthHeader, 10, 0)
+		if err != nil {
+			return nil, 0, err
+		}
+		return response.Body, int(length), nil
+	case response.StatusCode == http.StatusNotFound:
+		response.Body.Close()
+		return nil, 0, &BlobNotFoundError{Name: name, Digest: dgst}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return nil, 0, err
+		}
+		return nil, 0, &errs
+	default:
+		response.Body.Close()
+		return nil, 0, &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) InitiateBlobUpload(name string) (string, error) {
+	uploadURL, err := r.ub.BuildBlobUploadURL(name)
+	if err != nil {
+		return "", err
+	}
+
+	postRequest, err := http.NewRequest("POST", uploadURL, nil)
+	if err != nil {
+		return "", err
+	}
+
+	response, err := http.DefaultClient.Do(postRequest)
+	if err != nil {
+		return "", err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusAccepted:
+		return response.Header.Get("Location"), nil
+	// case response.StatusCode == http.StatusNotFound:
+	// return
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return "", err
+		}
+		return "", &errs
+	default:
+		return "", &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) GetBlobUploadStatus(location string) (int, int, error) {
+	response, err := http.Get(location)
+	if err != nil {
+		return 0, 0, err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusNoContent:
+		return parseRangeHeader(response.Header.Get("Range"))
+	case response.StatusCode == http.StatusNotFound:
+		return 0, 0, &BlobUploadNotFoundError{Location: location}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return 0, 0, err
+		}
+		return 0, 0, &errs
+	default:
+		return 0, 0, &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) UploadBlob(location string, blob io.ReadCloser, length int, dgst digest.Digest) error {
+	defer blob.Close()
+
+	putRequest, err := http.NewRequest("PUT", location, blob)
+	if err != nil {
+		return err
+	}
+
+	values := putRequest.URL.Query()
+	values.Set("digest", dgst.String())
+	putRequest.URL.RawQuery = values.Encode()
+
+	putRequest.Header.Set("Content-Type", "application/octet-stream")
+	putRequest.Header.Set("Content-Length", fmt.Sprint(length))
+
+	response, err := http.DefaultClient.Do(putRequest)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusCreated:
+		return nil
+	case response.StatusCode == http.StatusNotFound:
+		return &BlobUploadNotFoundError{Location: location}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return err
+		}
+		return &errs
+	default:
+		return &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) UploadBlobChunk(location string, blobChunk io.ReadCloser, length, startByte int) error {
+	defer blobChunk.Close()
+
+	putRequest, err := http.NewRequest("PUT", location, blobChunk)
+	if err != nil {
+		return err
+	}
+
+	endByte := startByte + length
+
+	putRequest.Header.Set("Content-Type", "application/octet-stream")
+	putRequest.Header.Set("Content-Length", fmt.Sprint(length))
+	putRequest.Header.Set("Content-Range",
+		fmt.Sprintf("%d-%d/%d", startByte, endByte, endByte))
+
+	response, err := http.DefaultClient.Do(putRequest)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusAccepted:
+		return nil
+	case response.StatusCode == http.StatusRequestedRangeNotSatisfiable:
+		lastValidRange, blobSize, err := parseRangeHeader(response.Header.Get("Range"))
+		if err != nil {
+			return err
+		}
+		return &BlobUploadInvalidRangeError{
+			Location:       location,
+			LastValidRange: lastValidRange,
+			BlobSize:       blobSize,
+		}
+	case response.StatusCode == http.StatusNotFound:
+		return &BlobUploadNotFoundError{Location: location}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return err
+		}
+		return &errs
+	default:
+		return &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) FinishChunkedBlobUpload(location string, length int, dgst digest.Digest) error {
+	putRequest, err := http.NewRequest("PUT", location, nil)
+	if err != nil {
+		return err
+	}
+
+	values := putRequest.URL.Query()
+	values.Set("digest", dgst.String())
+	putRequest.URL.RawQuery = values.Encode()
+
+	putRequest.Header.Set("Content-Type", "application/octet-stream")
+	putRequest.Header.Set("Content-Length", "0")
+	putRequest.Header.Set("Content-Range",
+		fmt.Sprintf("%d-%d/%d", length, length, length))
+
+	response, err := http.DefaultClient.Do(putRequest)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusCreated:
+		return nil
+	case response.StatusCode == http.StatusNotFound:
+		return &BlobUploadNotFoundError{Location: location}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return err
+		}
+		return &errs
+	default:
+		return &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+func (r *clientImpl) CancelBlobUpload(location string) error {
+	deleteRequest, err := http.NewRequest("DELETE", location, nil)
+	if err != nil {
+		return err
+	}
+
+	response, err := http.DefaultClient.Do(deleteRequest)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+
+	// TODO(bbland): handle other status codes, like 5xx errors
+	switch {
+	case response.StatusCode == http.StatusNoContent:
+		return nil
+	case response.StatusCode == http.StatusNotFound:
+		return &BlobUploadNotFoundError{Location: location}
+	case response.StatusCode >= 400 && response.StatusCode < 500:
+		var errs v2.Errors
+		decoder := json.NewDecoder(response.Body)
+		err = decoder.Decode(&errs)
+		if err != nil {
+			return err
+		}
+		return &errs
+	default:
+		return &UnexpectedHTTPStatusError{Status: response.Status}
+	}
+}
+
+// parseRangeHeader parses out the offset and length from a returned Range
+// header
+func parseRangeHeader(byteRangeHeader string) (int, int, error) {
+	submatches := patternRangeHeader.FindStringSubmatch(byteRangeHeader)
+	if submatches == nil || len(submatches) < 3 {
+		return 0, 0, fmt.Errorf("Malformed Range header")
+	}
+
+	offset, err := strconv.Atoi(submatches[1])
+	if err != nil {
+		return 0, 0, err
+	}
+	length, err := strconv.Atoi(submatches[2])
+	if err != nil {
+		return 0, 0, err
+	}
+	return offset, length, nil
+}

docs/client/client_test.go

@@ -0,0 +1,440 @@
+package client
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+
+	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/manifest"
+	"github.com/docker/distribution/testutil"
+)
+
+type testBlob struct {
+	digest   digest.Digest
+	contents []byte
+}
+
+func TestRangeHeaderParser(t *testing.T) {
+	const (
+		malformedRangeHeader = "bytes=0-A/C"
+		emptyRangeHeader     = ""
+		rFirst               = 100
+		rSecond              = 200
+	)
+
+	var (
+		wellformedRangeHeader = fmt.Sprintf("bytes=0-%d/%d", rFirst, rSecond)
+	)
+
+	if _, _, err := parseRangeHeader(malformedRangeHeader); err == nil {
+		t.Fatalf("malformedRangeHeader: error expected, got nil")
+	}
+
+	if _, _, err := parseRangeHeader(emptyRangeHeader); err == nil {
+		t.Fatalf("emptyRangeHeader: error expected, got nil")
+	}
+
+	first, second, err := parseRangeHeader(wellformedRangeHeader)
+	if err != nil {
+		t.Fatalf("wellformedRangeHeader: unexpected error %v", err)
+	}
+
+	if first != rFirst || second != rSecond {
+		t.Fatalf("Range has been parsed unproperly: %d/%d", first, second)
+	}
+
+}
+
+func TestPush(t *testing.T) {
+	name := "hello/world"
+	tag := "sometag"
+	testBlobs := []testBlob{
+		{
+			digest:   "tarsum.v2+sha256:12345",
+			contents: []byte("some contents"),
+		},
+		{
+			digest:   "tarsum.v2+sha256:98765",
+			contents: []byte("some other contents"),
+		},
+	}
+	uploadLocations := make([]string, len(testBlobs))
+	blobs := make([]manifest.FSLayer, len(testBlobs))
+	history := make([]manifest.History, len(testBlobs))
+
+	for i, blob := range testBlobs {
+		// TODO(bbland): this is returning the same location for all uploads,
+		// because we can't know which blob will get which location.
+		// It's sort of okay because we're using unique digests, but this needs
+		// to change at some point.
+		uploadLocations[i] = fmt.Sprintf("/v2/%s/blobs/test-uuid", name)
+		blobs[i] = manifest.FSLayer{BlobSum: blob.digest}
+		history[i] = manifest.History{V1Compatibility: blob.digest.String()}
+	}
+
+	m := &manifest.SignedManifest{
+		Manifest: manifest.Manifest{
+			Name:         name,
+			Tag:          tag,
+			Architecture: "x86",
+			FSLayers:     blobs,
+			History:      history,
+			Versioned: manifest.Versioned{
+				SchemaVersion: 1,
+			},
+		},
+	}
+	var err error
+	m.Raw, err = json.Marshal(m)
+
+	blobRequestResponseMappings := make([]testutil.RequestResponseMapping, 2*len(testBlobs))
+	for i, blob := range testBlobs {
+		blobRequestResponseMappings[2*i] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "POST",
+				Route:  "/v2/" + name + "/blobs/uploads/",
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusAccepted,
+				Headers: http.Header(map[string][]string{
+					"Location": {uploadLocations[i]},
+				}),
+			},
+		}
+		blobRequestResponseMappings[2*i+1] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "PUT",
+				Route:  uploadLocations[i],
+				QueryParams: map[string][]string{
+					"digest": {blob.digest.String()},
+				},
+				Body: blob.contents,
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusCreated,
+			},
+		}
+	}
+
+	handler := testutil.NewHandler(append(blobRequestResponseMappings, testutil.RequestResponseMapping{
+		Request: testutil.Request{
+			Method: "PUT",
+			Route:  "/v2/" + name + "/manifests/" + tag,
+			Body:   m.Raw,
+		},
+		Response: testutil.Response{
+			StatusCode: http.StatusOK,
+		},
+	}))
+	var server *httptest.Server
+
+	// HACK(stevvooe): Super hack to follow: the request response map approach
+	// above does not let us correctly format the location header to the
+	// server url. This handler intercepts and re-writes the location header
+	// to the server url.
+
+	hack := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w = &headerInterceptingResponseWriter{ResponseWriter: w, serverURL: server.URL}
+		handler.ServeHTTP(w, r)
+	})
+
+	server = httptest.NewServer(hack)
+	client, err := New(server.URL)
+	if err != nil {
+		t.Fatalf("error creating client: %v", err)
+	}
+	objectStore := &memoryObjectStore{
+		mutex:           new(sync.Mutex),
+		manifestStorage: make(map[string]*manifest.SignedManifest),
+		layerStorage:    make(map[digest.Digest]Layer),
+	}
+
+	for _, blob := range testBlobs {
+		l, err := objectStore.Layer(blob.digest)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		writer, err := l.Writer()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		writer.SetSize(len(blob.contents))
+		writer.Write(blob.contents)
+		writer.Close()
+	}
+
+	objectStore.WriteManifest(name, tag, m)
+
+	err = Push(client, objectStore, name, tag)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestPull(t *testing.T) {
+	name := "hello/world"
+	tag := "sometag"
+	testBlobs := []testBlob{
+		{
+			digest:   "tarsum.v2+sha256:12345",
+			contents: []byte("some contents"),
+		},
+		{
+			digest:   "tarsum.v2+sha256:98765",
+			contents: []byte("some other contents"),
+		},
+	}
+	blobs := make([]manifest.FSLayer, len(testBlobs))
+	history := make([]manifest.History, len(testBlobs))
+
+	for i, blob := range testBlobs {
+		blobs[i] = manifest.FSLayer{BlobSum: blob.digest}
+		history[i] = manifest.History{V1Compatibility: blob.digest.String()}
+	}
+
+	m := &manifest.SignedManifest{
+		Manifest: manifest.Manifest{
+			Name:         name,
+			Tag:          tag,
+			Architecture: "x86",
+			FSLayers:     blobs,
+			History:      history,
+			Versioned: manifest.Versioned{
+				SchemaVersion: 1,
+			},
+		},
+	}
+	manifestBytes, err := json.Marshal(m)
+
+	blobRequestResponseMappings := make([]testutil.RequestResponseMapping, len(testBlobs))
+	for i, blob := range testBlobs {
+		blobRequestResponseMappings[i] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "GET",
+				Route:  "/v2/" + name + "/blobs/" + blob.digest.String(),
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       blob.contents,
+			},
+		}
+	}
+
+	handler := testutil.NewHandler(append(blobRequestResponseMappings, testutil.RequestResponseMapping{
+		Request: testutil.Request{
+			Method: "GET",
+			Route:  "/v2/" + name + "/manifests/" + tag,
+		},
+		Response: testutil.Response{
+			StatusCode: http.StatusOK,
+			Body:       manifestBytes,
+		},
+	}))
+	server := httptest.NewServer(handler)
+	client, err := New(server.URL)
+	if err != nil {
+		t.Fatalf("error creating client: %v", err)
+	}
+	objectStore := &memoryObjectStore{
+		mutex:           new(sync.Mutex),
+		manifestStorage: make(map[string]*manifest.SignedManifest),
+		layerStorage:    make(map[digest.Digest]Layer),
+	}
+
+	err = Pull(client, objectStore, name, tag)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	m, err = objectStore.Manifest(name, tag)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mBytes, err := json.Marshal(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(mBytes) != string(manifestBytes) {
+		t.Fatal("Incorrect manifest")
+	}
+
+	for _, blob := range testBlobs {
+		l, err := objectStore.Layer(blob.digest)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		reader, err := l.Reader()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer reader.Close()
+
+		blobBytes, err := ioutil.ReadAll(reader)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if string(blobBytes) != string(blob.contents) {
+			t.Fatal("Incorrect blob")
+		}
+	}
+}
+
+func TestPullResume(t *testing.T) {
+	name := "hello/world"
+	tag := "sometag"
+	testBlobs := []testBlob{
+		{
+			digest:   "tarsum.v2+sha256:12345",
+			contents: []byte("some contents"),
+		},
+		{
+			digest:   "tarsum.v2+sha256:98765",
+			contents: []byte("some other contents"),
+		},
+	}
+	layers := make([]manifest.FSLayer, len(testBlobs))
+	history := make([]manifest.History, len(testBlobs))
+
+	for i, layer := range testBlobs {
+		layers[i] = manifest.FSLayer{BlobSum: layer.digest}
+		history[i] = manifest.History{V1Compatibility: layer.digest.String()}
+	}
+
+	m := &manifest.Manifest{
+		Name:         name,
+		Tag:          tag,
+		Architecture: "x86",
+		FSLayers:     layers,
+		History:      history,
+		Versioned: manifest.Versioned{
+			SchemaVersion: 1,
+		},
+	}
+	manifestBytes, err := json.Marshal(m)
+
+	layerRequestResponseMappings := make([]testutil.RequestResponseMapping, 2*len(testBlobs))
+	for i, blob := range testBlobs {
+		layerRequestResponseMappings[2*i] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "GET",
+				Route:  "/v2/" + name + "/blobs/" + blob.digest.String(),
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       blob.contents[:len(blob.contents)/2],
+				Headers: http.Header(map[string][]string{
+					"Content-Length": {fmt.Sprint(len(blob.contents))},
+				}),
+			},
+		}
+		layerRequestResponseMappings[2*i+1] = testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "GET",
+				Route:  "/v2/" + name + "/blobs/" + blob.digest.String(),
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       blob.contents[len(blob.contents)/2:],
+			},
+		}
+	}
+
+	for i := 0; i < 3; i++ {
+		layerRequestResponseMappings = append(layerRequestResponseMappings, testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method: "GET",
+				Route:  "/v2/" + name + "/manifests/" + tag,
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       manifestBytes,
+			},
+		})
+	}
+
+	handler := testutil.NewHandler(layerRequestResponseMappings)
+	server := httptest.NewServer(handler)
+	client, err := New(server.URL)
+	if err != nil {
+		t.Fatalf("error creating client: %v", err)
+	}
+	objectStore := &memoryObjectStore{
+		mutex:           new(sync.Mutex),
+		manifestStorage: make(map[string]*manifest.SignedManifest),
+		layerStorage:    make(map[digest.Digest]Layer),
+	}
+
+	for attempts := 0; attempts < 3; attempts++ {
+		err = Pull(client, objectStore, name, tag)
+		if err == nil {
+			break
+		}
+	}
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sm, err := objectStore.Manifest(name, tag)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mBytes, err := json.Marshal(sm)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if string(mBytes) != string(manifestBytes) {
+		t.Fatal("Incorrect manifest")
+	}
+
+	for _, blob := range testBlobs {
+		l, err := objectStore.Layer(blob.digest)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		reader, err := l.Reader()
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer reader.Close()
+
+		layerBytes, err := ioutil.ReadAll(reader)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if string(layerBytes) != string(blob.contents) {
+			t.Fatal("Incorrect blob")
+		}
+	}
+}
+
+// headerInterceptingResponseWriter is a hacky workaround to re-write the
+// location header to have the server url.
+type headerInterceptingResponseWriter struct {
+	http.ResponseWriter
+	serverURL string
+}
+
+func (hirw *headerInterceptingResponseWriter) WriteHeader(status int) {
+	location := hirw.Header().Get("Location")
+	if location != "" {
+		hirw.Header().Set("Location", hirw.serverURL+location)
+	}
+
+	hirw.ResponseWriter.WriteHeader(status)
+}

docs/client/errors.go

@@ -0,0 +1,79 @@
+package client
+
+import (
+	"fmt"
+
+	"github.com/docker/distribution/digest"
+)
+
+// RepositoryNotFoundError is returned when making an operation against a
+// repository that does not exist in the registry.
+type RepositoryNotFoundError struct {
+	Name string
+}
+
+func (e *RepositoryNotFoundError) Error() string {
+	return fmt.Sprintf("No repository found with Name: %s", e.Name)
+}
+
+// ImageManifestNotFoundError is returned when making an operation against a
+// given image manifest that does not exist in the registry.
+type ImageManifestNotFoundError struct {
+	Name string
+	Tag  string
+}
+
+func (e *ImageManifestNotFoundError) Error() string {
+	return fmt.Sprintf("No manifest found with Name: %s, Tag: %s",
+		e.Name, e.Tag)
+}
+
+// BlobNotFoundError is returned when making an operation against a given image
+// layer that does not exist in the registry.
+type BlobNotFoundError struct {
+	Name   string
+	Digest digest.Digest
+}
+
+func (e *BlobNotFoundError) Error() string {
+	return fmt.Sprintf("No blob found with Name: %s, Digest: %s",
+		e.Name, e.Digest)
+}
+
+// BlobUploadNotFoundError is returned when making a blob upload operation against an
+// invalid blob upload location url.
+// This may be the result of using a cancelled, completed, or stale upload
+// location.
+type BlobUploadNotFoundError struct {
+	Location string
+}
+
+func (e *BlobUploadNotFoundError) Error() string {
+	return fmt.Sprintf("No blob upload found at Location: %s", e.Location)
+}
+
+// BlobUploadInvalidRangeError is returned when attempting to upload an image
+// blob chunk that is out of order.
+// This provides the known BlobSize and LastValidRange which can be used to
+// resume the upload.
+type BlobUploadInvalidRangeError struct {
+	Location       string
+	LastValidRange int
+	BlobSize       int
+}
+
+func (e *BlobUploadInvalidRangeError) Error() string {
+	return fmt.Sprintf(
+		"Invalid range provided for upload at Location: %s. Last Valid Range: %d, Blob Size: %d",
+		e.Location, e.LastValidRange, e.BlobSize)
+}
+
+// UnexpectedHTTPStatusError is returned when an unexpected HTTP status is
+// returned when making a registry api call.
+type UnexpectedHTTPStatusError struct {
+	Status string
+}
+
+func (e *UnexpectedHTTPStatusError) Error() string {
+	return fmt.Sprintf("Received unexpected HTTP status: %s", e.Status)
+}

docs/client/objectstore.go

@@ -0,0 +1,239 @@
+package client
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/manifest"
+)
+
+var (
+	// ErrLayerAlreadyExists is returned when attempting to create a layer with
+	// a tarsum that is already in use.
+	ErrLayerAlreadyExists = fmt.Errorf("Layer already exists")
+
+	// ErrLayerLocked is returned when attempting to write to a layer which is
+	// currently being written to.
+	ErrLayerLocked = fmt.Errorf("Layer locked")
+)
+
+// ObjectStore is an interface which is designed to approximate the docker
+// engine storage. This interface is subject to change to conform to the
+// future requirements of the engine.
+type ObjectStore interface {
+	// Manifest retrieves the image manifest stored at the given repository name
+	// and tag
+	Manifest(name, tag string) (*manifest.SignedManifest, error)
+
+	// WriteManifest stores an image manifest at the given repository name and
+	// tag
+	WriteManifest(name, tag string, manifest *manifest.SignedManifest) error
+
+	// Layer returns a handle to a layer for reading and writing
+	Layer(dgst digest.Digest) (Layer, error)
+}
+
+// Layer is a generic image layer interface.
+// A Layer may not be written to if it is already complete.
+type Layer interface {
+	// Reader returns a LayerReader or an error if the layer has not been
+	// written to or is currently being written to.
+	Reader() (LayerReader, error)
+
+	// Writer returns a LayerWriter or an error if the layer has been fully
+	// written to or is currently being written to.
+	Writer() (LayerWriter, error)
+
+	// Wait blocks until the Layer can be read from.
+	Wait() error
+}
+
+// LayerReader is a read-only handle to a Layer, which exposes the CurrentSize
+// and full Size in addition to implementing the io.ReadCloser interface.
+type LayerReader interface {
+	io.ReadCloser
+
+	// CurrentSize returns the number of bytes written to the underlying Layer
+	CurrentSize() int
+
+	// Size returns the full size of the underlying Layer
+	Size() int
+}
+
+// LayerWriter is a write-only handle to a Layer, which exposes the CurrentSize
+// and full Size in addition to implementing the io.WriteCloser interface.
+// SetSize must be called on this LayerWriter before it can be written to.
+type LayerWriter interface {
+	io.WriteCloser
+
+	// CurrentSize returns the number of bytes written to the underlying Layer
+	CurrentSize() int
+
+	// Size returns the full size of the underlying Layer
+	Size() int
+
+	// SetSize sets the full size of the underlying Layer.
+	// This must be called before any calls to Write
+	SetSize(int) error
+}
+
+// memoryObjectStore is an in-memory implementation of the ObjectStore interface
+type memoryObjectStore struct {
+	mutex           *sync.Mutex
+	manifestStorage map[string]*manifest.SignedManifest
+	layerStorage    map[digest.Digest]Layer
+}
+
+func (objStore *memoryObjectStore) Manifest(name, tag string) (*manifest.SignedManifest, error) {
+	objStore.mutex.Lock()
+	defer objStore.mutex.Unlock()
+
+	manifest, ok := objStore.manifestStorage[name+":"+tag]
+	if !ok {
+		return nil, fmt.Errorf("No manifest found with Name: %q, Tag: %q", name, tag)
+	}
+	return manifest, nil
+}
+
+func (objStore *memoryObjectStore) WriteManifest(name, tag string, manifest *manifest.SignedManifest) error {
+	objStore.mutex.Lock()
+	defer objStore.mutex.Unlock()
+
+	objStore.manifestStorage[name+":"+tag] = manifest
+	return nil
+}
+
+func (objStore *memoryObjectStore) Layer(dgst digest.Digest) (Layer, error) {
+	objStore.mutex.Lock()
+	defer objStore.mutex.Unlock()
+
+	layer, ok := objStore.layerStorage[dgst]
+	if !ok {
+		layer = &memoryLayer{cond: sync.NewCond(new(sync.Mutex))}
+		objStore.layerStorage[dgst] = layer
+	}
+
+	return layer, nil
+}
+
+type memoryLayer struct {
+	cond         *sync.Cond
+	contents     []byte
+	expectedSize int
+	writing      bool
+}
+
+func (ml *memoryLayer) Reader() (LayerReader, error) {
+	ml.cond.L.Lock()
+	defer ml.cond.L.Unlock()
+
+	if ml.contents == nil {
+		return nil, fmt.Errorf("Layer has not been written to yet")
+	}
+	if ml.writing {
+		return nil, ErrLayerLocked
+	}
+
+	return &memoryLayerReader{ml: ml, reader: bytes.NewReader(ml.contents)}, nil
+}
+
+func (ml *memoryLayer) Writer() (LayerWriter, error) {
+	ml.cond.L.Lock()
+	defer ml.cond.L.Unlock()
+
+	if ml.contents != nil {
+		if ml.writing {
+			return nil, ErrLayerLocked
+		}
+		if ml.expectedSize == len(ml.contents) {
+			return nil, ErrLayerAlreadyExists
+		}
+	} else {
+		ml.contents = make([]byte, 0)
+	}
+
+	ml.writing = true
+	return &memoryLayerWriter{ml: ml, buffer: bytes.NewBuffer(ml.contents)}, nil
+}
+
+func (ml *memoryLayer) Wait() error {
+	ml.cond.L.Lock()
+	defer ml.cond.L.Unlock()
+
+	if ml.contents == nil {
+		return fmt.Errorf("No writer to wait on")
+	}
+
+	for ml.writing {
+		ml.cond.Wait()
+	}
+
+	return nil
+}
+
+type memoryLayerReader struct {
+	ml     *memoryLayer
+	reader *bytes.Reader
+}
+
+func (mlr *memoryLayerReader) Read(p []byte) (int, error) {
+	return mlr.reader.Read(p)
+}
+
+func (mlr *memoryLayerReader) Close() error {
+	return nil
+}
+
+func (mlr *memoryLayerReader) CurrentSize() int {
+	return len(mlr.ml.contents)
+}
+
+func (mlr *memoryLayerReader) Size() int {
+	return mlr.ml.expectedSize
+}
+
+type memoryLayerWriter struct {
+	ml     *memoryLayer
+	buffer *bytes.Buffer
+}
+
+func (mlw *memoryLayerWriter) Write(p []byte) (int, error) {
+	if mlw.ml.expectedSize == 0 {
+		return 0, fmt.Errorf("Must set size before writing to layer")
+	}
+	wrote, err := mlw.buffer.Write(p)
+	mlw.ml.contents = mlw.buffer.Bytes()
+	return wrote, err
+}
+
+func (mlw *memoryLayerWriter) Close() error {
+	mlw.ml.cond.L.Lock()
+	defer mlw.ml.cond.L.Unlock()
+
+	return mlw.close()
+}
+
+func (mlw *memoryLayerWriter) close() error {
+	mlw.ml.writing = false
+	mlw.ml.cond.Broadcast()
+	return nil
+}
+
+func (mlw *memoryLayerWriter) CurrentSize() int {
+	return len(mlw.ml.contents)
+}
+
+func (mlw *memoryLayerWriter) Size() int {
+	return mlw.ml.expectedSize
+}
+
+func (mlw *memoryLayerWriter) SetSize(size int) error {
+	if !mlw.ml.writing {
+		return fmt.Errorf("Layer is closed for writing")
+	}
+	mlw.ml.expectedSize = size
+	return nil
+}

docs/client/pull.go

@@ -0,0 +1,151 @@
+package client
+
+import (
+	"fmt"
+	"io"
+
+	log "github.com/Sirupsen/logrus"
+
+	"github.com/docker/distribution/manifest"
+)
+
+// simultaneousLayerPullWindow is the size of the parallel layer pull window.
+// A layer may not be pulled until the layer preceeding it by the length of the
+// pull window has been successfully pulled.
+const simultaneousLayerPullWindow = 4
+
+// Pull implements a client pull workflow for the image defined by the given
+// name and tag pair, using the given ObjectStore for local manifest and layer
+// storage
+func Pull(c Client, objectStore ObjectStore, name, tag string) error {
+	manifest, err := c.GetImageManifest(name, tag)
+	if err != nil {
+		return err
+	}
+	log.WithField("manifest", manifest).Info("Pulled manifest")
+
+	if len(manifest.FSLayers) != len(manifest.History) {
+		return fmt.Errorf("Length of history not equal to number of layers")
+	}
+	if len(manifest.FSLayers) == 0 {
+		return fmt.Errorf("Image has no layers")
+	}
+
+	errChans := make([]chan error, len(manifest.FSLayers))
+	for i := range manifest.FSLayers {
+		errChans[i] = make(chan error)
+	}
+
+	// To avoid leak of goroutines we must notify
+	// pullLayer goroutines about a cancelation,
+	// otherwise they will lock forever.
+	cancelCh := make(chan struct{})
+
+	// Iterate over each layer in the manifest, simultaneously pulling no more
+	// than simultaneousLayerPullWindow layers at a time. If an error is
+	// received from a layer pull, we abort the push.
+	for i := 0; i < len(manifest.FSLayers)+simultaneousLayerPullWindow; i++ {
+		dependentLayer := i - simultaneousLayerPullWindow
+		if dependentLayer >= 0 {
+			err := <-errChans[dependentLayer]
+			if err != nil {
+				log.WithField("error", err).Warn("Pull aborted")
+				close(cancelCh)
+				return err
+			}
+		}
+
+		if i < len(manifest.FSLayers) {
+			go func(i int) {
+				select {
+				case errChans[i] <- pullLayer(c, objectStore, name, manifest.FSLayers[i]):
+				case <-cancelCh: // no chance to recv until cancelCh's closed
+				}
+			}(i)
+		}
+	}
+
+	err = objectStore.WriteManifest(name, tag, manifest)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error":    err,
+			"manifest": manifest,
+		}).Warn("Unable to write image manifest")
+		return err
+	}
+
+	return nil
+}
+
+func pullLayer(c Client, objectStore ObjectStore, name string, fsLayer manifest.FSLayer) error {
+	log.WithField("layer", fsLayer).Info("Pulling layer")
+
+	layer, err := objectStore.Layer(fsLayer.BlobSum)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to write local layer")
+		return err
+	}
+
+	layerWriter, err := layer.Writer()
+	if err == ErrLayerAlreadyExists {
+		log.WithField("layer", fsLayer).Info("Layer already exists")
+		return nil
+	}
+	if err == ErrLayerLocked {
+		log.WithField("layer", fsLayer).Info("Layer download in progress, waiting")
+		layer.Wait()
+		return nil
+	}
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to write local layer")
+		return err
+	}
+	defer layerWriter.Close()
+
+	if layerWriter.CurrentSize() > 0 {
+		log.WithFields(log.Fields{
+			"layer":       fsLayer,
+			"currentSize": layerWriter.CurrentSize(),
+			"size":        layerWriter.Size(),
+		}).Info("Layer partially downloaded, resuming")
+	}
+
+	layerReader, length, err := c.GetBlob(name, fsLayer.BlobSum, layerWriter.CurrentSize())
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to download layer")
+		return err
+	}
+	defer layerReader.Close()
+
+	layerWriter.SetSize(layerWriter.CurrentSize() + length)
+
+	_, err = io.Copy(layerWriter, layerReader)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to download layer")
+		return err
+	}
+	if layerWriter.CurrentSize() != layerWriter.Size() {
+		log.WithFields(log.Fields{
+			"size":        layerWriter.Size(),
+			"currentSize": layerWriter.CurrentSize(),
+			"layer":       fsLayer,
+		}).Warn("Layer invalid size")
+		return fmt.Errorf(
+			"Wrote incorrect number of bytes for layer %v. Expected %d, Wrote %d",
+			fsLayer, layerWriter.Size(), layerWriter.CurrentSize(),
+		)
+	}
+	return nil
+}

docs/client/push.go

@@ -0,0 +1,137 @@
+package client
+
+import (
+	"fmt"
+
+	log "github.com/Sirupsen/logrus"
+	"github.com/docker/distribution/manifest"
+)
+
+// simultaneousLayerPushWindow is the size of the parallel layer push window.
+// A layer may not be pushed until the layer preceeding it by the length of the
+// push window has been successfully pushed.
+const simultaneousLayerPushWindow = 4
+
+type pushFunction func(fsLayer manifest.FSLayer) error
+
+// Push implements a client push workflow for the image defined by the given
+// name and tag pair, using the given ObjectStore for local manifest and layer
+// storage
+func Push(c Client, objectStore ObjectStore, name, tag string) error {
+	manifest, err := objectStore.Manifest(name, tag)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"name":  name,
+			"tag":   tag,
+		}).Info("No image found")
+		return err
+	}
+
+	errChans := make([]chan error, len(manifest.FSLayers))
+	for i := range manifest.FSLayers {
+		errChans[i] = make(chan error)
+	}
+
+	cancelCh := make(chan struct{})
+
+	// Iterate over each layer in the manifest, simultaneously pushing no more
+	// than simultaneousLayerPushWindow layers at a time. If an error is
+	// received from a layer push, we abort the push.
+	for i := 0; i < len(manifest.FSLayers)+simultaneousLayerPushWindow; i++ {
+		dependentLayer := i - simultaneousLayerPushWindow
+		if dependentLayer >= 0 {
+			err := <-errChans[dependentLayer]
+			if err != nil {
+				log.WithField("error", err).Warn("Push aborted")
+				close(cancelCh)
+				return err
+			}
+		}
+
+		if i < len(manifest.FSLayers) {
+			go func(i int) {
+				select {
+				case errChans[i] <- pushLayer(c, objectStore, name, manifest.FSLayers[i]):
+				case <-cancelCh: // recv broadcast notification about cancelation
+				}
+			}(i)
+		}
+	}
+
+	err = c.PutImageManifest(name, tag, manifest)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error":    err,
+			"manifest": manifest,
+		}).Warn("Unable to upload manifest")
+		return err
+	}
+
+	return nil
+}
+
+func pushLayer(c Client, objectStore ObjectStore, name string, fsLayer manifest.FSLayer) error {
+	log.WithField("layer", fsLayer).Info("Pushing layer")
+
+	layer, err := objectStore.Layer(fsLayer.BlobSum)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to read local layer")
+		return err
+	}
+
+	layerReader, err := layer.Reader()
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to read local layer")
+		return err
+	}
+	defer layerReader.Close()
+
+	if layerReader.CurrentSize() != layerReader.Size() {
+		log.WithFields(log.Fields{
+			"layer":       fsLayer,
+			"currentSize": layerReader.CurrentSize(),
+			"size":        layerReader.Size(),
+		}).Warn("Local layer incomplete")
+		return fmt.Errorf("Local layer incomplete")
+	}
+
+	length, err := c.BlobLength(name, fsLayer.BlobSum)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to check existence of remote layer")
+		return err
+	}
+	if length >= 0 {
+		log.WithField("layer", fsLayer).Info("Layer already exists")
+		return nil
+	}
+
+	location, err := c.InitiateBlobUpload(name)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to upload layer")
+		return err
+	}
+
+	err = c.UploadBlob(location, layerReader, int(layerReader.CurrentSize()), fsLayer.BlobSum)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"error": err,
+			"layer": fsLayer,
+		}).Warn("Unable to upload layer")
+		return err
+	}
+
+	return nil
+}