From 4edbd5322cd2f180610cd707f2d5585fb1977911 Mon Sep 17 00:00:00 2001
From: Matthew Hooker <mwhooker@gmail.com>
Date: Wed, 23 Aug 2017 14:09:39 -0700
Subject: [PATCH] docker: stream uploads over stdin

Only write to a tempfile if we don't have a stat struct
---
 builder/docker/communicator.go    | 90 +++++++++++++++++++++++--------
 communicator/none/communicator.go |  3 +-
 2 files changed, 70 insertions(+), 23 deletions(-)

diff --git a/builder/docker/communicator.go b/builder/docker/communicator.go
index d6b37a1a0..16fc405c1 100644
--- a/builder/docker/communicator.go
+++ b/builder/docker/communicator.go
@@ -60,39 +60,85 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 	return nil
 }
 
+// Upload uploads a file to the docker container
 func (c *Communicator) Upload(dst string, src io.Reader, fi *os.FileInfo) error {
+	if fi == nil {
+		return c.uploadReader(dst, src)
+	}
+	return c.uploadFile(dst, src, fi)
+}
+
+// uploadReader writes an io.Reader to a temporary file before uploading
+func (c *Communicator) uploadReader(dst string, src io.Reader) error {
 	// Create a temporary file to store the upload
 	tempfile, err := ioutil.TempFile(c.HostDir, "upload")
 	if err != nil {
-		return err
+		return fmt.Errorf("Failed to open temp file for writing: %s", err)
 	}
 	defer os.Remove(tempfile.Name())
+	defer tempfile.Close()
 
-	// Copy the contents to the temporary file
-	_, err = io.Copy(tempfile, src)
+	if _, err := io.Copy(tempfile, src); err != nil {
+		return fmt.Errorf("Failed to copy upload file to tempfile: %s", err)
+	}
+	tempfile.Seek(0, 0)
+	fi, err := tempfile.Stat()
+	if err != nil {
+		return fmt.Errorf("Error getting tempfile info: %s", err)
+	}
+	return c.uploadFile(dst, tempfile, &fi)
+}
+
+// uploadFile uses docker cp to copy the file from the host to the container
+func (c *Communicator) uploadFile(dst string, src io.Reader, fi *os.FileInfo) error {
+
+	// command format: docker cp /path/to/infile containerid:/path/to/outfile
+	log.Printf("Copying to %s on container %s.", dst, c.ContainerId)
+
+	localCmd := exec.Command("docker", "cp", "-",
+		fmt.Sprintf("%s:%s", c.ContainerId, filepath.Dir(dst)))
+
+	stderrP, err := localCmd.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("Failed to open pipe: %s", err)
+	}
+
+	stdin, err := localCmd.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("Failed to open pipe: %s", err)
+	}
+
+	if err := localCmd.Start(); err != nil {
+		return err
+	}
+
+	archive := tar.NewWriter(stdin)
+	header, err := tar.FileInfoHeader(*fi, "")
+	if err != nil {
+		return err
+	}
+	header.Name = filepath.Base(dst)
+	archive.WriteHeader(header)
+	numBytes, err := io.Copy(archive, src)
+	if err != nil {
+		return fmt.Errorf("Failed to pipe upload: %s", err)
+	}
+	log.Printf("Copied %d bytes for %s", numBytes, dst)
+
+	if err := archive.Close(); err != nil {
+		return fmt.Errorf("Failed to close archive: %s", err)
+	}
+	if err := stdin.Close(); err != nil {
+		return fmt.Errorf("Failed to close stdin: %s", err)
+	}
+
+	stderrOut, err := ioutil.ReadAll(stderrP)
 	if err != nil {
 		return err
 	}
 
-	if fi != nil {
-		tempfile.Chmod((*fi).Mode())
-	}
-	tempfile.Close()
-
-	// Use docker cp to copy the file from the host to the container
-	// command format: docker cp /path/to/infile containerid:/path/to/outfile
-	cmd := exec.Command("docker", "cp", tempfile.Name(), fmt.Sprintf("%s:%s", c.ContainerId, dst))
-
-	log.Printf("Copying %s to %s on container %s.", tempfile.Name(), dst, c.ContainerId)
-	if err := cmd.Start(); err != nil {
-		return err
-	}
-
-	if err := cmd.Wait(); err != nil {
-		err = fmt.Errorf("Error uploading %s: %s",
-			tempfile.Name(),
-			err)
-		return err
+	if err := localCmd.Wait(); err != nil {
+		return fmt.Errorf("Failed to upload to '%s' in container: %s. %s.", dst, stderrOut, err)
 	}
 
 	return nil
diff --git a/communicator/none/communicator.go b/communicator/none/communicator.go
index 4e08aba1b..5c14a4283 100644
--- a/communicator/none/communicator.go
+++ b/communicator/none/communicator.go
@@ -2,9 +2,10 @@ package none
 
 import (
 	"errors"
-	"github.com/hashicorp/packer/packer"
 	"io"
 	"os"
+
+	"github.com/hashicorp/packer/packer"
 )
 
 type comm struct {