Allows layers to be partially pulled and resumed

Adds a sort of contrived test for resumable pulls

client/client_test.go

@@ -117,6 +117,7 @@ func TestPush(t *testing.T) {
 			t.Fatal(err)
 		}
 
+		writer.SetSize(len(blob.contents))
 		writer.Write(blob.contents)
 		writer.Close()
 	}
@@ -235,3 +236,133 @@ func TestPull(t *testing.T) {
 		}
 	}
 }
+
+func TestPullResume(t *testing.T) {
+	name := "hello/world"
+	tag := "sometag"
+	testBlobs := []testBlob{
+		{
+			digest:   "12345",
+			contents: []byte("some contents"),
+		},
+		{
+			digest:   "98765",
+			contents: []byte("some other contents"),
+		},
+	}
+	layers := make([]registry.FSLayer, len(testBlobs))
+	history := make([]registry.ManifestHistory, len(testBlobs))
+
+	for i, layer := range testBlobs {
+		layers[i] = registry.FSLayer{BlobSum: layer.digest}
+		history[i] = registry.ManifestHistory{V1Compatibility: layer.digest.String()}
+	}
+
+	manifest := &registry.ImageManifest{
+		Name:          name,
+		Tag:           tag,
+		Architecture:  "x86",
+		FSLayers:      layers,
+		History:       history,
+		SchemaVersion: 1,
+	}
+	manifestBytes, err := json.Marshal(manifest)
+
+	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 + "/blob/" + 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 + "/blob/" + 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.RequestResponseMap{
+			testutil.RequestResponseMapping{
+				Request: testutil.Request{
+					Method: "GET",
+					Route:  "/v2/" + name + "/manifest/" + tag,
+				},
+				Response: testutil.Response{
+					StatusCode: http.StatusOK,
+					Body:       manifestBytes,
+				},
+			},
+		}...)
+	}
+
+	handler := testutil.NewHandler(layerRequestResponseMappings)
+	server := httptest.NewServer(handler)
+	client := New(server.URL)
+	objectStore := &memoryObjectStore{
+		mutex:           new(sync.Mutex),
+		manifestStorage: make(map[string]*registry.ImageManifest),
+		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)
+	}
+
+	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()
+
+		layerBytes, err := ioutil.ReadAll(reader)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if string(layerBytes) != string(blob.contents) {
+			t.Fatal("Incorrect blob")
+		}
+	}
+}

client/objectstore.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"sync"
 
 	"github.com/docker/docker-registry"
@@ -39,20 +38,49 @@ type ObjectStore interface {
 }
 
 // Layer is a generic image layer interface.
-// A Layer may only be written to once
+// A Layer may not be written to if it is already complete.
 type Layer interface {
-	// Reader returns an io.ReadCloser which reads the contents of the layer
-	Reader() (io.ReadCloser, error)
+	// 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 an io.WriteCloser which may write the contents of the
-	// layer. This method may only be called once per Layer, and the contents
-	// are made available on Close
-	Writer() (io.WriteCloser, 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 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
@@ -94,66 +122,112 @@ func (objStore *memoryObjectStore) Layer(dgst digest.Digest) (Layer, error) {
 
 type memoryLayer struct {
 	cond         *sync.Cond
-	buffer  *bytes.Buffer
-	written bool
+	contents     []byte
+	expectedSize int
+	writing      bool
 }
 
-func (ml *memoryLayer) Writer() (io.WriteCloser, error) {
+func (ml *memoryLayer) Reader() (LayerReader, error) {
 	ml.cond.L.Lock()
 	defer ml.cond.L.Unlock()
 
-	if ml.buffer != nil {
-		if !ml.written {
-			return nil, ErrLayerLocked
-		}
-		return nil, ErrLayerAlreadyExists
-	}
-
-	ml.buffer = new(bytes.Buffer)
-	return &memoryLayerWriter{cond: ml.cond, buffer: ml.buffer, done: &ml.written}, nil
-}
-
-func (ml *memoryLayer) Reader() (io.ReadCloser, error) {
-	ml.cond.L.Lock()
-	defer ml.cond.L.Unlock()
-
-	if ml.buffer == nil {
+	if ml.contents == nil {
 		return nil, fmt.Errorf("Layer has not been written to yet")
 	}
-	if !ml.written {
+	if ml.writing {
 		return nil, ErrLayerLocked
 	}
 
-	return ioutil.NopCloser(bytes.NewReader(ml.buffer.Bytes())), nil
+	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.buffer == nil {
+	if ml.contents == nil {
 		return fmt.Errorf("No writer to wait on")
 	}
 
-	for !ml.written {
+	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 {
-	cond   *sync.Cond
+	ml     *memoryLayer
 	buffer *bytes.Buffer
-	done   *bool
 }
 
 func (mlw *memoryLayerWriter) Write(p []byte) (int, error) {
-	return mlw.buffer.Write(p)
+	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.done = true
-	mlw.cond.Broadcast()
+	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
 }

client/pull.go

@@ -89,7 +89,7 @@ func pullLayer(c Client, objectStore ObjectStore, name string, fsLayer registry.
 		return err
 	}
 
-	writer, err := layer.Writer()
+	layerWriter, err := layer.Writer()
 	if err == ErrLayerAlreadyExists {
 		log.WithField("layer", fsLayer).Info("Layer already exists")
 		return nil
@@ -106,9 +106,17 @@ func pullLayer(c Client, objectStore ObjectStore, name string, fsLayer registry.
 		}).Warn("Unable to write local layer")
 		return err
 	}
-	defer writer.Close()
+	defer layerWriter.Close()
 
-	layerReader, length, err := c.GetBlob(name, fsLayer.BlobSum, 0)
+	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,
@@ -118,7 +126,9 @@ func pullLayer(c Client, objectStore ObjectStore, name string, fsLayer registry.
 	}
 	defer layerReader.Close()
 
-	copied, err := io.Copy(writer, layerReader)
+	layerWriter.SetSize(layerWriter.CurrentSize() + length)
+
+	_, err = io.Copy(layerWriter, layerReader)
 	if err != nil {
 		log.WithFields(log.Fields{
 			"error": err,
@@ -126,15 +136,15 @@ func pullLayer(c Client, objectStore ObjectStore, name string, fsLayer registry.
 		}).Warn("Unable to download layer")
 		return err
 	}
-	if copied != int64(length) {
+	if layerWriter.CurrentSize() != layerWriter.Size() {
 		log.WithFields(log.Fields{
-			"expected": length,
-			"written":  copied,
+			"size":        layerWriter.Size(),
+			"currentSize": layerWriter.CurrentSize(),
 			"layer":       fsLayer,
-		}).Warn("Wrote incorrect number of bytes for layer")
+		}).Warn("Layer invalid size")
 		return fmt.Errorf(
 			"Wrote incorrect number of bytes for layer %v. Expected %d, Wrote %d",
-			fsLayer, length, copied,
+			fsLayer, layerWriter.Size(), layerWriter.CurrentSize(),
 		)
 	}
 	return nil

client/push.go

@@ -1,9 +1,7 @@
 package client
 
 import (
-	"bytes"
-	"io"
-	"io/ioutil"
+	"errors"
 
 	"github.com/docker/docker-registry"
 
@@ -96,14 +94,13 @@ func pushLayer(c Client, objectStore ObjectStore, name string, fsLayer registry.
 	}
 	defer layerReader.Close()
 
-	layerBuffer := new(bytes.Buffer)
-	layerSize, err := io.Copy(layerBuffer, layerReader)
-	if err != nil {
+	if layerReader.CurrentSize() != layerReader.Size() {
 		log.WithFields(log.Fields{
-			"error": err,
 			"layer":       fsLayer,
-		}).Warn("Unable to read local layer")
-		return err
+			"currentSize": layerReader.CurrentSize(),
+			"size":        layerReader.Size(),
+		}).Warn("Local layer incomplete")
+		return errors.New("Local layer incomplete")
 	}
 
 	length, err := c.BlobLength(name, fsLayer.BlobSum)
@@ -128,7 +125,7 @@ func pushLayer(c Client, objectStore ObjectStore, name string, fsLayer registry.
 		return err
 	}
 
-	err = c.UploadBlob(location, ioutil.NopCloser(layerBuffer), int(layerSize), fsLayer.BlobSum)
+	err = c.UploadBlob(location, layerReader, int(layerReader.CurrentSize()), fsLayer.BlobSum)
 	if err != nil {
 		log.WithFields(log.Fields{
 			"error": err,