Disable compression for build. More space usage but much faster upload

Docker-DCO-1.0-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)

buildfile.go

@@ -594,11 +594,12 @@ func (b *buildFile) Build(context io.Reader) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	b.context = &utils.TarSum{Reader: context}
+	b.context = &utils.TarSum{Reader: context, DisableCompression: true}
 	if err := archive.Untar(b.context, tmpdirPath, nil); err != nil {
 		return "", err
 	}
 	defer os.RemoveAll(tmpdirPath)
+
 	b.contextPath = tmpdirPath
 	filename := path.Join(tmpdirPath, "Dockerfile")
 	if _, err := os.Stat(filename); os.IsNotExist(err) {

utils/tarsum.go

@@ -17,7 +17,7 @@ type TarSum struct {
 	io.Reader
 	tarR               *tar.Reader
 	tarW               *tar.Writer
-	gz          *gzip.Writer
+	gz                 writeCloseFlusher
 	bufTar             *bytes.Buffer
 	bufGz              *bytes.Buffer
 	h                  hash.Hash
@@ -25,6 +25,24 @@ type TarSum struct {
 	currentFile        string
 	finished           bool
 	first              bool
+	DisableCompression bool
+}
+
+type writeCloseFlusher interface {
+	io.WriteCloser
+	Flush() error
+}
+
+type nopCloseFlusher struct {
+	io.Writer
+}
+
+func (n *nopCloseFlusher) Close() error {
+	return nil
+}
+
+func (n *nopCloseFlusher) Flush() error {
+	return nil
 }
 
 func (ts *TarSum) encodeHeader(h *tar.Header) error {
@@ -57,7 +75,11 @@ func (ts *TarSum) Read(buf []byte) (int, error) {
 		ts.bufGz = bytes.NewBuffer([]byte{})
 		ts.tarR = tar.NewReader(ts.Reader)
 		ts.tarW = tar.NewWriter(ts.bufTar)
+		if !ts.DisableCompression {
 			ts.gz = gzip.NewWriter(ts.bufGz)
+		} else {
+			ts.gz = &nopCloseFlusher{Writer: ts.bufGz}
+		}
 		ts.h = sha256.New()
 		ts.h.Reset()
 		ts.first = true