builder/docker: Communicator.Start doesn't block

builder/docker/communicator.go

@@ -11,6 +11,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strconv"
+	"sync"
 	"syscall"
 	"time"
 )
@@ -19,6 +20,8 @@ type Communicator struct {
 	ContainerId  string
 	HostDir      string
 	ContainerDir string
+
+	lock sync.Mutex
 }
 
 func (c *Communicator) Start(remote *packer.RemoteCmd) error {
@@ -38,6 +41,68 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 	exitCodePath := outputFile.Name() + "-exit"
 	defer os.Remove(exitCodePath)
 
+	cmd := exec.Command("docker", "attach", c.ContainerId)
+	stdin_w, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	// Run the actual command in a goroutine so that Start doesn't block
+	go c.run(cmd, remote, stdin_w, outputFile, exitCodePath)
+
+	return nil
+}
+
+func (c *Communicator) Upload(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
+	}
+	defer os.Remove(tempfile.Name())
+
+	// Copy the contents to the temporary file
+	_, err = io.Copy(tempfile, src)
+	tempfile.Close()
+	if err != nil {
+		return err
+	}
+
+	// Copy the file into place by copying the temporary file we put
+	// into the shared folder into the proper location in the container
+	cmd := &packer.RemoteCmd{
+		Command: fmt.Sprintf("cp %s/%s %s", c.ContainerDir,
+			filepath.Base(tempfile.Name()), dst),
+	}
+
+	if err := c.Start(cmd); err != nil {
+		return err
+	}
+
+	// Wait for the copy to complete
+	cmd.Wait()
+	if cmd.ExitStatus != 0 {
+		return fmt.Errorf("Upload failed with non-zero exit status: %d", cmd.ExitStatus)
+	}
+
+	return nil
+}
+
+func (c *Communicator) UploadDir(dst string, src string, exclude []string) error {
+	return nil
+}
+
+func (c *Communicator) Download(src string, dst io.Writer) error {
+	return nil
+}
+
+// Runs the given command and blocks until completion
+func (c *Communicator) run(cmd *exec.Cmd, remote *packer.RemoteCmd, stdin_w io.WriteCloser, outputFile *os.File, exitCodePath string) {
+	// For Docker, remote communication must be serialized since it
+	// only supports single execution.
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
 	// Modify the remote command so that all the output of the commands
 	// go to a single file and so that the exit code is redirected to
 	// a single file. This lets us determine both when the command
@@ -49,15 +114,12 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 		filepath.Join(c.ContainerDir, filepath.Base(outputFile.Name())),
 		filepath.Join(c.ContainerDir, filepath.Base(exitCodePath)))
 
-	cmd := exec.Command("docker", "attach", c.ContainerId)
-	stdin_w, err := cmd.StdinPipe()
-	if err != nil {
-		return err
-	}
-
+	// Start the command
 	log.Printf("Executing in container %s: %#v", c.ContainerId, remoteCmd)
 	if err := cmd.Start(); err != nil {
-		return err
+		log.Printf("Error executing: %s", err)
+		remote.SetExited(254)
+		return
 	}
 
 	go func() {
@@ -73,7 +135,7 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 		stdin_w.Write([]byte(remoteCmd + "\n"))
 	}()
 
-	err = cmd.Wait()
+	err := cmd.Wait()
 	if exitErr, ok := err.(*exec.ExitError); ok {
 		exitStatus := 1
 
@@ -86,7 +148,7 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 		// Say that we ended, since if Docker itself failed, then
 		// the command must've not run, or so we assume
 		remote.SetExited(exitStatus)
-		return nil
+		return
 	}
 
 	// Wait for the exit code to appear in our file...
@@ -103,19 +165,25 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 	// Read the exit code
 	exitRaw, err := ioutil.ReadFile(exitCodePath)
 	if err != nil {
-		return err
+		log.Printf("Error executing: %s", err)
+		remote.SetExited(254)
+		return
 	}
 
 	exitStatus, err := strconv.ParseInt(string(bytes.TrimSpace(exitRaw)), 10, 0)
 	if err != nil {
-		return err
+		log.Printf("Error executing: %s", err)
+		remote.SetExited(254)
+		return
 	}
 	log.Printf("Executed command exit status: %d", exitStatus)
 
 	// Read the output
 	f, err := os.Open(outputFile.Name())
 	if err != nil {
-		return err
+		log.Printf("Error executing: %s", err)
+		remote.SetExited(254)
+		return
 	}
 	defer f.Close()
 
@@ -124,7 +192,9 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 	} else {
 		output, err := ioutil.ReadAll(f)
 		if err != nil {
-			return err
+			log.Printf("Error executing: %s", err)
+			remote.SetExited(254)
+			return
 		}
 
 		log.Printf("Command output: %s", string(output))
@@ -132,48 +202,4 @@ func (c *Communicator) Start(remote *packer.RemoteCmd) error {
 
 	// Finally, we're done
 	remote.SetExited(int(exitStatus))
-
-	return nil
-}
-
-func (c *Communicator) Upload(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
-	}
-	defer os.Remove(tempfile.Name())
-
-	// Copy the contents to the temporary file
-	_, err = io.Copy(tempfile, src)
-	tempfile.Close()
-	if err != nil {
-		return err
-	}
-
-	// TODO(mitchellh): Copy the file into place
-	cmd := &packer.RemoteCmd{
-		Command: fmt.Sprintf("cp %s/%s %s", c.ContainerDir,
-			filepath.Base(tempfile.Name()), dst),
-	}
-
-	if err := c.Start(cmd); err != nil {
-		return err
-	}
-
-	// Wait for the copy to complete
-	cmd.Wait()
-	if cmd.ExitStatus != 0 {
-		return fmt.Errorf("Upload failed with non-zero exit status: %d", cmd.ExitStatus)
-	}
-
-	return nil
-}
-
-func (c *Communicator) UploadDir(dst string, src string, exclude []string) error {
-	return nil
-}
-
-func (c *Communicator) Download(src string, dst io.Writer) error {
-	return nil
 }