also refactored out a container module, and got rid of the state comp…

…letely

pkg/container/container.go

@@ -0,0 +1,45 @@
+package container
+
+import (
+	"errors"
+
+	"github.com/docker/docker/client"
+	"golang.org/x/net/context"
+)
+
+// Options represents the configuration for running a docker container to
+// be used as backdrop.
+type Options struct {
+	Client      *client.Client
+	Image       string
+	Name        string
+	Interactive bool
+	Interpreter []string
+	Entrypoint  string
+	Script      string
+	Command     []string
+	Environment []string
+	Volumes     []string
+	VolumesFrom []string
+	User        string
+	WorkingDir  string
+}
+
+// Run runs a docker container as backdrop.
+func Run(ctx context.Context, options Options) error {
+	if options.Client == nil {
+		return errors.New("client may not be nil")
+	}
+
+	containerID, err := createContainer(ctx, options)
+	if err != nil {
+		return err
+	}
+
+	err = uploadEntrypoint(ctx, containerID, options)
+	if err != nil {
+		return err
+	}
+
+	return runContainer(ctx, containerID, options)
+}

pkg/container/create.go

@@ -0,0 +1,49 @@
+package container
+
+import (
+	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/api/types/network"
+	"golang.org/x/net/context"
+)
+
+func createContainer(ctx context.Context, options Options) (string, error) {
+	response, err := options.Client.ContainerCreate(
+		ctx,
+		&container.Config{
+			User:         options.User,
+			AttachStdin:  true,
+			AttachStdout: true,
+			AttachStderr: true,
+			Tty:          true,
+			OpenStdin:    true,
+			StdinOnce:    true,
+			Env:          options.Environment,
+			Cmd:          options.Command,
+			Image:        options.Image,
+			WorkingDir:   options.WorkingDir,
+			Entrypoint:   getEntrypoint(options),
+		},
+		&container.HostConfig{
+			AutoRemove:  true,
+			Binds:       options.Volumes,
+			VolumesFrom: options.VolumesFrom,
+		},
+		&network.NetworkingConfig{},
+		options.Name,
+	)
+	if err != nil {
+		return "", err
+	}
+	return response.ID, nil
+}
+
+func getEntrypoint(options Options) []string {
+	entrypoint := []string{"/bin/sh"}
+	if len(options.Interpreter) > 0 {
+		entrypoint = options.Interpreter
+	}
+	if !options.Interactive {
+		entrypoint = append(entrypoint, options.Entrypoint)
+	}
+	return entrypoint
+}

pkg/state/entrypoint.go → pkg/container/entrypoint.go

@@ -1,4 +1,4 @@
-package state
+package container
 
 import (
 	"archive/tar"
@@ -9,19 +9,7 @@ import (
 	"golang.org/x/net/context"
 )
 
-// EnsureEntrypoint makes sure the entrypoint script ist uploaded to the
-// container.
-func (state *State) EnsureEntrypoint(ctx context.Context) error {
-	config := state.Config
-	client, err := state.EnsureClient()
-	if err != nil {
-		return err
-	}
-	container, err := state.EnsureContainer(ctx)
-	if err != nil {
-		return err
-	}
-
+func uploadEntrypoint(ctx context.Context, containerID string, options Options) error {
 	reader, writer := io.Pipe()
 	defer func() {
 		if err := reader.Close(); err != nil {
@@ -30,9 +18,9 @@ func (state *State) EnsureEntrypoint(ctx context.Context) error {
 	}()
 
 	go func() {
-		err := client.CopyToContainer(
+		err := options.Client.CopyToContainer(
 			ctx,
-			container,
+			containerID,
 			"/",
 			reader,
 			types.CopyToContainerOptions{},
@@ -43,15 +31,15 @@ func (state *State) EnsureEntrypoint(ctx context.Context) error {
 	}()
 
 	tarWriter := tar.NewWriter(writer)
-	err = tarWriter.WriteHeader(&tar.Header{
-		Name: state.Entrypoint,
+	err := tarWriter.WriteHeader(&tar.Header{
+		Name: options.Entrypoint,
 		Mode: 0600,
-		Size: int64(len(config.Script)),
+		Size: int64(len(options.Script)),
 	})
 	if err != nil {
 		return err
 	}
-	_, err = tarWriter.Write([]byte(state.Config.Script))
+	_, err = tarWriter.Write([]byte(options.Script))
 	if err != nil {
 		return err
 	}

pkg/state/container_run.go → pkg/container/run.go

@@ -1,4 +1,4 @@
-package state
+package container
 
 import (
 	"io"
@@ -11,23 +11,8 @@ import (
 	"golang.org/x/net/context"
 )
 
-// EnsureRun makes sure the command is performed.
-func (state *State) EnsureRun(ctx context.Context) error {
-	client, err := state.EnsureClient()
-	if err != nil {
-		return err
-	}
-	containerID, err := state.EnsureContainer(ctx)
-	if err != nil {
-		return err
-	}
-	defer state.EnsureCleanup(ctx)
-	err = state.EnsureEntrypoint(ctx)
-	if err != nil {
-		return err
-	}
-
-	attach, err := client.ContainerAttach(
+func runContainer(ctx context.Context, containerID string, options Options) error {
+	attach, err := options.Client.ContainerAttach(
 		ctx,
 		containerID,
 		types.ContainerAttachOptions{
@@ -101,13 +86,13 @@ func (state *State) EnsureRun(ctx context.Context) error {
 		}
 	}()
 
-	waitChannel, waitErrorChannel := client.ContainerWait(
+	waitChannel, waitErrorChannel := options.Client.ContainerWait(
 		ctx,
 		containerID,
 		container.WaitConditionRemoved,
 	)
 
-	err = client.ContainerStart(
+	err = options.Client.ContainerStart(
 		ctx,
 		containerID,
 		types.ContainerStartOptions{},