Update apply diff to support context cancellation

Allows cancellation of apply when the grpc service issues a cancel.
Adds a timing log for apply.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

archive/tar.go

@@ -107,6 +107,12 @@ func Apply(ctx context.Context, root string, r io.Reader) (int64, error) {
 
 	// Iterate through the files in the archive.
 	for {
+		select {
+		case <-ctx.Done():
+			return 0, ctx.Err()
+		default:
+		}
+
 		hdr, err := tr.Next()
 		if err == io.EOF {
 			// end of tar archive
@@ -455,9 +461,8 @@ func createTarFile(ctx context.Context, path, extractDir string, hdr *tar.Header
 		if err != nil {
 			return err
 		}
-		buf := bufferPool.Get().([]byte)
-		_, err = io.CopyBuffer(file, reader, buf)
-		bufferPool.Put(buf)
+
+		_, err = copyBuffered(ctx, file, reader)
 		if err1 := file.Close(); err == nil {
 			err = err1
 		}
@@ -524,3 +529,41 @@ func createTarFile(ctx context.Context, path, extractDir string, hdr *tar.Header
 
 	return chtimes(path, boundTime(latestTime(hdr.AccessTime, hdr.ModTime)), boundTime(hdr.ModTime))
 }
+
+func copyBuffered(ctx context.Context, dst io.Writer, src io.Reader) (written int64, err error) {
+	buf := bufferPool.Get().([]byte)
+	defer bufferPool.Put(buf)
+
+	for {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+			return
+		default:
+		}
+
+		nr, er := src.Read(buf)
+		if nr > 0 {
+			nw, ew := dst.Write(buf[0:nr])
+			if nw > 0 {
+				written += int64(nw)
+			}
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				err = er
+			}
+			break
+		}
+	}
+	return written, err
+
+}

diff/walking/differ.go

@@ -24,6 +24,7 @@ import (
 	digest "github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 )
 
@@ -63,7 +64,18 @@ func NewWalkingDiff(store content.Store) (diff.Differ, error) {
 // Apply applies the content associated with the provided digests onto the
 // provided mounts. Archive content will be extracted and decompressed if
 // necessary.
-func (s *walkingDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []mount.Mount) (ocispec.Descriptor, error) {
+func (s *walkingDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts []mount.Mount) (d ocispec.Descriptor, err error) {
+	t1 := time.Now()
+	defer func() {
+		if err == nil {
+			log.G(ctx).WithFields(logrus.Fields{
+				"d":     time.Now().Sub(t1),
+				"dgst":  desc.Digest,
+				"size":  desc.Size,
+				"media": desc.MediaType,
+			}).Debugf("diff applied")
+		}
+	}()
 	var isCompressed bool
 	switch desc.MediaType {
 	case ocispec.MediaTypeImageLayer, images.MediaTypeDockerSchema2Layer: