Beispiel #1
0
func Boot(client *docker.Client, opt *docker.CreateContainerOptions,
	exitCh chan error) (*docker.Container, error) {
	log.Debugf("Creating container for image %s", opt.Config.Image)
	container, err := client.CreateContainer(*opt)
	if err != nil {
		return container, err
	}

	log.Debugf("Starting container %s", container.ID)
	go func() {
		exitCh <- dockerpty.Start(client, container, opt.HostConfig)
	}()

	trial := 0
	for {
		container, err = client.InspectContainer(container.ID)
		if container.State.StartedAt.Unix() > 0 {
			break
		}
		if trial > 30 {
			return container, fmt.Errorf("container %s seems not started. state=%#v", container.ID, container.State)
		}
		trial += 1
		time.Sleep(time.Duration(trial*100) * time.Millisecond)
	}
	log.Debugf("container state=%#v", container.State)
	return container, nil
}
Beispiel #2
0
func launchContainer(client *docker.Client, containerImageName, name string) (*docker.Container, error) {

	images, err := client.ListImages(docker.ListImagesOptions{Filter: containerImageName})

	if err != nil {
		return nil, err
	}

	targetImageId := images[0].ID
	container, err := client.CreateContainer(docker.CreateContainerOptions{
		Name: name,
		Config: &docker.Config{
			Image: targetImageId,
		},
	})

	if err != nil {
		return nil, err
	}

	if err := client.StartContainer(container.ID, &docker.HostConfig{PublishAllPorts: true}); err != nil {
		return nil, err
	}

	return client.InspectContainer(container.ID)
}
Beispiel #3
0
// imageFSMetadata creates a container and reads the filesystem metadata out of the archive.
func imageFSMetadata(c *docker.Client, name string) (map[string]*tar.Header, error) {
	container, err := c.CreateContainer(docker.CreateContainerOptions{Name: name + "-export", Config: &docker.Config{Image: name}})
	if err != nil {
		return nil, err
	}
	defer c.RemoveContainer(docker.RemoveContainerOptions{ID: container.ID, RemoveVolumes: true, Force: true})

	ch := make(chan struct{})
	result := make(map[string]*tar.Header)
	r, w := io.Pipe()
	go func() {
		defer close(ch)
		out := tar.NewReader(r)
		for {
			h, err := out.Next()
			if err != nil {
				if err == io.EOF {
					w.Close()
				} else {
					w.CloseWithError(err)
				}
				break
			}
			result[h.Name] = h
		}
	}()
	if err := c.ExportContainer(docker.ExportContainerOptions{ID: container.ID, OutputStream: w}); err != nil {
		return nil, err
	}
	<-ch
	return result, nil
}
// createGremlin creates the gremlin container using the docker client.
// It is used only in the test code.
func createGremlin(client *docker.Client) (*docker.Container, error) {
	container, err := client.CreateContainer(docker.CreateContainerOptions{
		Config: &docker.Config{
			Image: testImageName,
		},
	})

	return container, err
}
Beispiel #5
0
func runContainer(client *dockerapi.Client, createOpts dockerapi.CreateContainerOptions, startConfig *dockerapi.HostConfig) (string, error) {
	container, err := client.CreateContainer(createOpts)
	if err != nil {
		return "", err
	}

	err = client.StartContainer(container.ID, startConfig)
	// return container ID even if there is an error, so caller can clean up container if desired
	return container.ID, err
}
Beispiel #6
0
func createContainer(client *docker.Client, opts docker.CreateContainerOptions) (c *container, err error) {
	var dockerInfo *docker.Container
	dockerInfo, err = client.CreateContainer(opts)
	if err == nil {
		c = &container{
			client: client,
			id:     dockerInfo.ID,
		}
	}
	return
}
func createContainers(client *docker.Client, num int, labels map[string]string) {
	for i := 0; i < num; i++ {
		name := "test_container_" + strconv.FormatInt(time.Now().UnixNano(), 10)
		dockerOpts := docker.CreateContainerOptions{
			Name: name,
			Config: &docker.Config{
				Image:  "ubuntu",
				Labels: labels,
			},
		}
		client.CreateContainer(dockerOpts)
	}
}
Beispiel #8
0
// Run runs cmd in the given image using the docker client cl. It mounts cwd into containerMount in the running container and sends on the following channels:
//
// - rmContainerCh: a function closure that the receiver should call, after they receive on errCh or exitCodeCh, to remove the container. this is commonly done with a 'defer'
// - stdOut: all logs from STDOUT in the container. this may never receive
// - stdErr: all logs from STDERR in the container. this may never receive
// - exitCodeCh: the exit code of the container
// - errCh: any error in setting up or running the container. if errCh receives, exitCodeCh may not receive
func Run(
	cl *docker.Client,
	image *Image,
	taskName,
	cwd,
	containerMount,
	cmd string,
	env []string,
	rmContainerCh chan<- func(),
	stdOut chan<- Log,
	stdErr chan<- Log,
	exitCodeCh chan<- int,
	errCh chan<- error,
) {

	mounts := []docker.Mount{
		{Name: "pwd", Source: cwd, Destination: containerMount, Mode: "rxw"},
	}
	cmdSpl := strings.Split(cmd, " ")

	containerName := NewContainerName(taskName, cwd)
	createContainerOpts, hostConfig := CreateAndStartContainerOpts(image.String(), containerName, cmdSpl, env, mounts, containerMount)
	if err := EnsureImage(cl, image.String(), func() (io.Writer, error) {
		return os.Stdout, nil
	}); err != nil {
		errCh <- err
		return
	}

	container, err := cl.CreateContainer(createContainerOpts)
	if err != nil {
		errCh <- err
	}

	rmContainerCh <- func() {
		if err := cl.RemoveContainer(docker.RemoveContainerOptions{ID: container.ID, Force: true}); err != nil {
			log.Warn("Error removing container %s (%s)", container.ID, err)
		}
	}

	log.Debug(CmdStr(createContainerOpts, hostConfig))

	attachOpts := AttachToContainerOpts(container.ID, NewChanWriter(stdOut), NewChanWriter(stdErr))
	// attach before the container starts, so we get all the logs etc...
	go AttachAndWait(cl, container.ID, attachOpts, exitCodeCh, errCh)

	if startErr := cl.StartContainer(container.ID, &hostConfig); startErr != nil {
		errCh <- err
		return
	}
}
Beispiel #9
0
func CreateContainer(client *docker.Client, config *Config, image string, standby int, env string) (*docker.Container, error) {
	id, _ := randomHex(20)
	volumePath := fmt.Sprintf("%s/%s", config.SharedPath, id)
	name := fmt.Sprintf("bitrun-%v", time.Now().UnixNano())

	if err := os.Mkdir(volumePath, 0777); err != nil {
		return nil, err
	}

	opts := docker.CreateContainerOptions{
		Name: name,
		HostConfig: &docker.HostConfig{
			Binds: []string{
				volumePath + ":/code",
				volumePath + ":/tmp",
			},
			ReadonlyRootfs: true,
			Memory:         config.MemoryLimit,
			MemorySwap:     0,
		},
		Config: &docker.Config{
			Hostname:        "bitrun",
			Image:           image,
			Labels:          map[string]string{"id": id},
			AttachStdout:    false,
			AttachStderr:    false,
			AttachStdin:     false,
			Tty:             false,
			NetworkDisabled: config.NetworkDisabled,
			WorkingDir:      "/code",
			Cmd:             []string{"sleep", fmt.Sprintf("%v", standby)},
			Env:             strings.Split(env, "\n"),
		},
	}

	container, err := client.CreateContainer(opts)
	if err == nil {
		container.Config = opts.Config
	}

	return container, err
}
func CreateAndRemoveContainers(client *docker.Client) string {
	name := newContainerName()
	dockerOpts := docker.CreateContainerOptions{
		Name: name,
		Config: &docker.Config{
			Image: "ubuntu",
		},
	}
	container, err := client.CreateContainer(dockerOpts)
	if err != nil {
		panic(fmt.Sprintf("Error create containers: %v", err))
	}
	removeOpts := docker.RemoveContainerOptions{
		ID: container.ID,
	}
	if err := client.RemoveContainer(removeOpts); err != nil {
		panic(fmt.Sprintf("Error remove containers: %v", err))
	}
	return container.ID
}
func CreateContainers(client *docker.Client, num int) []string {
	ids := []string{}
	for i := 0; i < num; i++ {
		name := newContainerName()
		dockerOpts := docker.CreateContainerOptions{
			Name: name,
			Config: &docker.Config{
				AttachStderr: false,
				AttachStdin:  false,
				AttachStdout: false,
				Tty:          true,
				Cmd:          []string{"/bin/bash"},
				Image:        "ubuntu",
			},
		}
		container, err := client.CreateContainer(dockerOpts)
		if err != nil {
			panic(fmt.Sprintf("Error create containers: %v", err))
		}
		ids = append(ids, container.ID)
	}
	return ids
}
Beispiel #12
0
// createAndStartRouterContainer is responsible for deploying the router image in docker.  It assumes that all router images
// will use a command line flag that can take --master which points to the master url
func createAndStartRouterContainer(dockerCli *dockerClient.Client, masterIp string) (containerId string, err error) {
	ports := []string{"80", "443"}
	portBindings := make(map[dockerClient.Port][]dockerClient.PortBinding)
	exposedPorts := map[dockerClient.Port]struct{}{}

	for _, p := range ports {
		dockerPort := dockerClient.Port(p + "/tcp")

		portBindings[dockerPort] = []dockerClient.PortBinding{
			{
				HostPort: p,
			},
		}

		exposedPorts[dockerPort] = struct{}{}
	}

	containerOpts := dockerClient.CreateContainerOptions{
		Config: &dockerClient.Config{
			Image:        getRouterImage(),
			Cmd:          []string{"--master=" + masterIp, "--loglevel=4"},
			ExposedPorts: exposedPorts,
		},
	}

	container, err := dockerCli.CreateContainer(containerOpts)

	if err != nil {
		return "", err
	}

	dockerHostCfg := &dockerClient.HostConfig{NetworkMode: "host", PortBindings: portBindings}
	err = dockerCli.StartContainer(container.ID, dockerHostCfg)

	if err != nil {
		return "", err
	}

	running := false

	//wait for it to start
	for i := 0; i < dockerRetries; i++ {
		c, err := dockerCli.InspectContainer(container.ID)

		if err != nil {
			return "", err
		}

		if c.State.Running {
			running = true
			break
		}
		time.Sleep(time.Second * dockerWaitSeconds)
	}

	if !running {
		return "", errors.New("Container did not start after 3 tries!")
	}

	return container.ID, nil
}
Beispiel #13
0
// StartDockerContainer starts a new Lever container for the specified
// environment and service.
func StartDockerContainer(
	docker *dockerapi.Client, environment string, service string,
	instanceID string, codeVersion int64, isAdmin bool,
	leverConfig *core.LeverConfig) (
	containerID string, node string, err error) {
	codeDir := HostCodeDirPath(environment, service, codeVersion)
	binds := []string{codeDir + ":/leveros/custcode:ro,Z"}
	env := []string{
		"LEVEROS_ENVIRONMENT=" + environment,
		"LEVEROS_SERVICE=" + service,
		"LEVEROS_INSTANCE_ID=" + instanceID,
		"LEVEROS_CODE_VERSION=" + strconv.Itoa(int(codeVersion)),
		"LEVEROS_INTERNAL_ENV_SUFFIX=" +
			core.InternalEnvironmentSuffixFlag.Get(),
	}
	if isAdmin {
		// This is used by admin to make deployments.
		binds = append(
			binds, LeverCodeHostDirFlag.Get()+":/leveros/custcodetree:Z")
	}

	// Configure logging.
	var logConfig dockerapi.LogConfig
	if devlogger.DisableFlag.Get() {
		logConfig.Type = "none"
	} else {
		// TODO: Should use scale.Dereference... to get IP of syslog server
		//       and shard by env+service.
		tag := fmt.Sprintf(
			"%s/%s/%d/%s", environment, service, codeVersion, instanceID)
		logConfig.Type = "syslog"
		logConfig.Config = map[string]string{
			"syslog-address":  "tcp://127.0.0.1:6514",
			"syslog-facility": "user",
			"tag":             tag,
			"syslog-format":   "rfc5424",
		}
	}

	memoryBytes := int64(leverConfig.InstanceMemoryMB) * 1000 * 1000
	memAndSwapBytes := memoryBytes     // No swap.
	kernelMemBytes := memoryBytes / 10 // Allow 10% memory for kernel.

	// Entry point.
	entry := leverConfig.EntryPoint
	if leverConfig.JSEntryPoint != "" {
		// Trigger GC in node when garbage reaches 90% of memory.
		maxGarbage := strconv.Itoa(
			int(float32(leverConfig.InstanceMemoryMB) * 0.9))
		// Set entry point for node.
		entry = []string{
			"node", "--optimize_for_size", "--max_old_space_size=" + maxGarbage,
			"--gc_interval=100",
			"/leveros/js/leveros-server/compiled/lib/serve.js",
			leverConfig.JSEntryPoint,
		}
	}

	container, err := docker.CreateContainer(dockerapi.CreateContainerOptions{
		Name: "leveros_" + instanceID,
		Config: &dockerapi.Config{
			Image:        "leveros/levercontainer:latest",
			Cmd:          entry,
			Env:          env,
			KernelMemory: kernelMemBytes,
			Labels: map[string]string{
				"com.leveros.environment": environment,
				"com.leveros.service":     service,
				"com.leveros.instanceid":  instanceID,
				"com.leveros.codeversion": strconv.Itoa(int(codeVersion)),
			},
		},
		// TODO: Documentation for these here:
		//       https://docs.docker.com/engine/reference/api/docker_remote_api_v1.23/#create-a-container
		// TODO: Also check if need to set limits on IO operations (blkio).
		// TODO: Should allow to write to disk, but limit amount of disk space.
		HostConfig: &dockerapi.HostConfig{
			ReadonlyRootfs:   true,
			Binds:            binds,
			CapDrop:          []string{"all"},
			NetworkMode:      "none",
			Ulimits:          []dockerapi.ULimit{},          // TODO
			SecurityOpt:      []string{"no-new-privileges"}, // TODO
			LogConfig:        logConfig,
			Memory:           memoryBytes,
			MemorySwap:       memAndSwapBytes,
			MemorySwappiness: 0,
			CPUShares:        0, // TODO
			CPUPeriod:        0, // TODO
			CPUQuota:         0, // TODO
		},
	})
	if err != nil {
		logger.WithFields("err", err).Debug(
			"Error trying to create container")
		return "", "", err
	}

	// Get info about the node it was allocated to by Docker Swarm.
	container, err = docker.InspectContainer(container.ID)
	if err != nil {
		removeErr := RemoveDockerContainer(docker, container.ID)
		if removeErr != nil {
			logger.WithFields(
				"containerID", containerID,
				"err", removeErr,
			).Error("Error trying to remove container after previous error")
		}
		return "", "", err
	}
	if container.Node != nil {
		node = container.Node.Name
	} else {
		// In a dev/testing (non-swarm) environment.
		logger.Warning(
			"Using non-swarm node. " +
				"YOU SHOULD NEVER SEE THIS IN PRODUCTION.")
		node = "leverosconsul"
	}

	// Start the container.
	err = docker.StartContainer(container.ID, nil)
	if err != nil {
		removeErr := RemoveDockerContainer(docker, container.ID)
		if removeErr != nil {
			logger.WithFields(
				"containerID", containerID,
				"err", removeErr,
			).Error("Error trying to remove container after failed to start")
		}
		return "", "", err
	}

	// Need to disconnect it from the "none" network before being able to
	// connect it to its local environment network.
	err = DisconnectFromDockerEnvNetwork(docker, container.ID, "none")
	if err != nil {
		removeErr := RemoveDockerContainer(docker, container.ID)
		if removeErr != nil {
			logger.WithFields(
				"containerID", containerID,
				"err", removeErr,
			).Error("Error trying to remove container after previous error")
		}
		return "", "", err
	}

	return container.ID, node, nil
}
Beispiel #14
0
// createAndStartRouterContainer is responsible for deploying the router image in docker.  It assumes that all router images
// will use a command line flag that can take --master which points to the master url
func createAndStartRouterContainer(dockerCli *dockerClient.Client, masterIp string, routerStatsPort int, reloadInterval int) (containerId string, err error) {
	ports := []string{"80", "443"}
	if routerStatsPort > 0 {
		ports = append(ports, fmt.Sprintf("%d", routerStatsPort))
	}

	portBindings := make(map[dockerClient.Port][]dockerClient.PortBinding)
	exposedPorts := map[dockerClient.Port]struct{}{}

	for _, p := range ports {
		dockerPort := dockerClient.Port(p + "/tcp")

		portBindings[dockerPort] = []dockerClient.PortBinding{
			{
				HostPort: p,
			},
		}

		exposedPorts[dockerPort] = struct{}{}
	}

	copyEnv := []string{
		"ROUTER_EXTERNAL_HOST_HOSTNAME",
		"ROUTER_EXTERNAL_HOST_USERNAME",
		"ROUTER_EXTERNAL_HOST_PASSWORD",
		"ROUTER_EXTERNAL_HOST_HTTP_VSERVER",
		"ROUTER_EXTERNAL_HOST_HTTPS_VSERVER",
		"ROUTER_EXTERNAL_HOST_INSECURE",
		"ROUTER_EXTERNAL_HOST_PRIVKEY",
	}

	env := []string{
		fmt.Sprintf("STATS_PORT=%d", routerStatsPort),
		fmt.Sprintf("STATS_USERNAME=%s", statsUser),
		fmt.Sprintf("STATS_PASSWORD=%s", statsPassword),
		fmt.Sprintf("DEFAULT_CERTIFICATE=%s", defaultCert),
	}

	reloadIntVar := fmt.Sprintf("RELOAD_INTERVAL=%ds", reloadInterval)
	env = append(env, reloadIntVar)

	for _, name := range copyEnv {
		val := os.Getenv(name)
		if len(val) > 0 {
			env = append(env, name+"="+val)
		}
	}

	vols := ""
	hostVols := []string{}

	privkeyFilename := os.Getenv("ROUTER_EXTERNAL_HOST_PRIVKEY")
	if len(privkeyFilename) != 0 {
		vols = privkeyFilename
		privkeyBindmount := fmt.Sprintf("%[1]s:%[1]s", privkeyFilename)
		hostVols = append(hostVols, privkeyBindmount)
	}

	binary := os.Getenv("ROUTER_OPENSHIFT_BINARY")
	if len(binary) != 0 {
		hostVols = append(hostVols, fmt.Sprintf("%[1]s:/usr/bin/openshift", binary))
	}

	containerOpts := dockerClient.CreateContainerOptions{
		Config: &dockerClient.Config{
			Image:        getRouterImage(),
			Cmd:          []string{"--master=" + masterIp, "--loglevel=4"},
			Env:          env,
			ExposedPorts: exposedPorts,
			VolumesFrom:  vols,
		},
		HostConfig: &dockerClient.HostConfig{
			Binds: hostVols,
		},
	}

	container, err := dockerCli.CreateContainer(containerOpts)

	if err != nil {
		return "", err
	}

	dockerHostCfg := &dockerClient.HostConfig{NetworkMode: "host", PortBindings: portBindings}
	err = dockerCli.StartContainer(container.ID, dockerHostCfg)

	if err != nil {
		return "", err
	}

	//wait for it to start
	if err := wait.Poll(time.Millisecond*100, time.Second*30, func() (bool, error) {
		c, err := dockerCli.InspectContainer(container.ID)
		if err != nil {
			return false, err
		}
		return c.State.Running, nil
	}); err != nil {
		return "", err
	}
	return container.ID, nil
}
Beispiel #15
0
// createAndStartRouterContainer is responsible for deploying the router image in docker.  It assumes that all router images
// will use a command line flag that can take --master which points to the master url
func createAndStartRouterContainer(dockerCli *dockerClient.Client, masterIp string, routerStatsPort int) (containerId string, err error) {
	ports := []string{"80", "443"}
	if routerStatsPort > 0 {
		ports = append(ports, fmt.Sprintf("%d", routerStatsPort))
	}

	portBindings := make(map[dockerClient.Port][]dockerClient.PortBinding)
	exposedPorts := map[dockerClient.Port]struct{}{}

	for _, p := range ports {
		dockerPort := dockerClient.Port(p + "/tcp")

		portBindings[dockerPort] = []dockerClient.PortBinding{
			{
				HostPort: p,
			},
		}

		exposedPorts[dockerPort] = struct{}{}
	}

	copyEnv := []string{
		"ROUTER_EXTERNAL_HOST_HOSTNAME",
		"ROUTER_EXTERNAL_HOST_USERNAME",
		"ROUTER_EXTERNAL_HOST_PASSWORD",
		"ROUTER_EXTERNAL_HOST_HTTP_VSERVER",
		"ROUTER_EXTERNAL_HOST_HTTPS_VSERVER",
		"ROUTER_EXTERNAL_HOST_INSECURE",
		"ROUTER_EXTERNAL_HOST_PRIVKEY",
	}

	env := []string{
		fmt.Sprintf("STATS_PORT=%d", routerStatsPort),
		fmt.Sprintf("STATS_USERNAME=%s", statsUser),
		fmt.Sprintf("STATS_PASSWORD=%s", statsPassword),
	}

	for _, name := range copyEnv {
		val := os.Getenv(name)
		if len(val) > 0 {
			env = append(env, name+"="+val)
		}
	}

	vols := ""
	hostVols := []string{}

	privkeyFilename := os.Getenv("ROUTER_EXTERNAL_HOST_PRIVKEY")
	if len(privkeyFilename) != 0 {
		vols = privkeyFilename
		privkeyBindmount := fmt.Sprintf("%[1]s:%[1]s", privkeyFilename)
		hostVols = append(hostVols, privkeyBindmount)
	}

	binary := os.Getenv("ROUTER_OPENSHIFT_BINARY")
	if len(binary) != 0 {
		hostVols = append(hostVols, fmt.Sprintf("%[1]s:/usr/bin/openshift", binary))
	}

	containerOpts := dockerClient.CreateContainerOptions{
		Config: &dockerClient.Config{
			Image:        getRouterImage(),
			Cmd:          []string{"--master=" + masterIp, "--loglevel=4"},
			Env:          env,
			ExposedPorts: exposedPorts,
			VolumesFrom:  vols,
		},
		HostConfig: &dockerClient.HostConfig{
			Binds: hostVols,
		},
	}

	container, err := dockerCli.CreateContainer(containerOpts)

	if err != nil {
		return "", err
	}

	dockerHostCfg := &dockerClient.HostConfig{NetworkMode: "host", PortBindings: portBindings}
	err = dockerCli.StartContainer(container.ID, dockerHostCfg)

	if err != nil {
		return "", err
	}

	running := false

	//wait for it to start
	for i := 0; i < dockerRetries; i++ {
		time.Sleep(time.Second * dockerWaitSeconds)

		c, err := dockerCli.InspectContainer(container.ID)

		if err != nil {
			return "", err
		}

		if c.State.Running {
			running = true
			break
		}
	}

	if !running {
		return "", errors.New("Container did not start after 3 tries!")
	}

	return container.ID, nil
}
// createAndExtractImage creates a docker container based on the option's image with containerName.
// It will then insepct the container and image and then attempt to extract the image to
// option's destination path.  If the destination path is empty it will write to a temp directory
// and update the option's destination path with a /var/tmp directory.  /var/tmp is used to
// try and ensure it is a non-in-memory tmpfs.
func (i *defaultImageInspector) createAndExtractImage(client *docker.Client, containerName string) (*docker.Image, error) {
	container, err := client.CreateContainer(docker.CreateContainerOptions{
		Name: containerName,
		Config: &docker.Config{
			Image: i.opts.Image,
			// For security purpose we don't define any entrypoint and command
			Entrypoint: []string{""},
			Cmd:        []string{""},
		},
	})
	if err != nil {
		return nil, fmt.Errorf("Unable to create docker container: %v\n", err)
	}

	// delete the container when we are done extracting it
	defer func() {
		client.RemoveContainer(docker.RemoveContainerOptions{
			ID: container.ID,
		})
	}()

	containerMetadata, err := client.InspectContainer(container.ID)
	if err != nil {
		return nil, fmt.Errorf("Unable to get docker container information: %v\n", err)
	}

	imageMetadata, err := client.InspectImage(containerMetadata.Image)
	if err != nil {
		return imageMetadata, fmt.Errorf("Unable to get docker image information: %v\n", err)
	}

	if i.opts.DstPath, err = createOutputDir(i.opts.DstPath, "image-inspector-"); err != nil {
		return imageMetadata, err
	}

	reader, writer := io.Pipe()
	// handle closing the reader/writer in the method that creates them
	defer writer.Close()
	defer reader.Close()

	log.Printf("Extracting image %s to %s", i.opts.Image, i.opts.DstPath)

	// start the copy function first which will block after the first write while waiting for
	// the reader to read.
	errorChannel := make(chan error)
	go func() {
		errorChannel <- client.CopyFromContainer(docker.CopyFromContainerOptions{
			Container:    container.ID,
			OutputStream: writer,
			Resource:     "/",
		})
	}()

	// block on handling the reads here so we ensure both the write and the reader are finished
	// (read waits until an EOF or error occurs).
	handleTarStream(reader, i.opts.DstPath)

	// capture any error from the copy, ensures both the handleTarStream and CopyFromContainer
	// are done.
	err = <-errorChannel
	if err != nil {
		return imageMetadata, fmt.Errorf("Unable to extract container: %v\n", err)
	}

	return imageMetadata, nil
}