Add loading of existing container

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

container.go

@@ -42,6 +42,43 @@ func NewContainer(root, id string, m Mount, s *specs.Spec, driver ExecutionDrive
 	}, nil
 }
 
+func LoadContainer(root, id string, driver ExecutionDriver) (*Container, error) {
+	path := filepath.Join(root, id)
+	spec, err := loadSpec(path)
+	if err != nil {
+		return nil, err
+	}
+	process, err := driver.Load(id)
+	if err != nil {
+		return nil, err
+	}
+	// TODO: load exec processes
+	return &Container{
+		id:     id,
+		path:   path,
+		s:      spec,
+		driver: driver,
+		init: &Process{
+			d:      process,
+			driver: driver,
+		},
+	}, nil
+}
+
+func loadSpec(path string) (*specs.Spec, error) {
+	f, err := os.Open(filepath.Join(path, "config.json"))
+	if err != nil {
+		return nil, err
+	}
+	var s specs.Spec
+	err = json.NewDecoder(f).Decode(&s)
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+	return &s, nil
+}
+
 type Container struct {
 	mu   sync.Mutex
 	id   string

example/main.go

@@ -29,7 +29,11 @@ func getContainerRootfs() containerkit.Mount {
 
 func runContainer() error {
 	// create a new runc runtime that implements the ExecutionDriver interface
-	driver, err := oci.New("/run/runc", "runc", "/tmp/runc")
+	driver, err := oci.New(oci.Opts{
+		Root:    "/run/runc",
+		Name:    "runc",
+		LogFile: "/tmp/runc",
+	})
 	if err != nil {
 		return err
 	}
@@ -89,6 +93,15 @@ func runContainer() error {
 		logrus.Infof("process %d returned with %d", i, procStatus)
 	}
 
+	container, err = containerkit.LoadContainer(
+		"/var/lib/containerkit", /* container root */
+		"test",                  /* container id */
+		driver,                  /* the exec driver to use for the container */
+	)
+	if err != nil {
+		return err
+	}
+
 	// wait for it to exit and get the exit status
 	logrus.Info("wait container")
 	status, err := container.Wait()
@@ -151,7 +164,7 @@ func spec(id string) *specs.Spec {
 		},
 		Process: specs.Process{
 			Env:             env,
-			Args:            []string{"sleep", "10"},
+			Args:            []string{"sleep", "30"},
 			Terminal:        false,
 			Cwd:             "/",
 			NoNewPrivileges: true,

execution.go

@@ -11,4 +11,5 @@ type ExecutionDriver interface {
 	Start(*Container) error
 	Delete(*Container) error
 	Exec(*Container, *Process) (ProcessDelegate, error)
+	Load(id string) (ProcessDelegate, error)
 }

oci/oci.go

@@ -9,18 +9,27 @@ import (
 	"path/filepath"
 	"strconv"
 	"syscall"
+	"time"
 
 	"github.com/docker/containerkit"
 )
 
-func New(root, name, log string) (*OCIRuntime, error) {
+type Opts struct {
-	if err := os.MkdirAll(root, 0711); err != nil {
+	Name    string
+	Root    string
+	Args    []string
+	LogFile string
+}
+
+func New(opts Opts) (*OCIRuntime, error) {
+	if err := os.MkdirAll(opts.Root, 0711); err != nil {
 		return nil, err
 	}
 	return &OCIRuntime{
-		root: root,
+		root: opts.Root,
-		log:  log,
+		log:  opts.LogFile,
-		name: name,
+		name: opts.Name,
+		args: opts.Args,
 	}, nil
 }
 
@@ -32,6 +41,8 @@ type OCIRuntime struct {
 	name string
 	// log is the path to the log files for the containers
 	log string
+	// args specifies additional arguments to the OCI runtime
+	args []string
 }
 
 func (r *OCIRuntime) Create(c *containerkit.Container) (containerkit.ProcessDelegate, error) {
@@ -88,11 +99,34 @@ func (r *OCIRuntime) Exec(c *containerkit.Container, p *containerkit.Process) (c
 	return newProcess(i)
 }
 
+type state struct {
+	ID          string            `json:"id"`
+	Pid         int               `json:"pid"`
+	Status      string            `json:"status"`
+	Bundle      string            `json:"bundle"`
+	Rootfs      string            `json:"rootfs"`
+	Created     time.Time         `json:"created"`
+	Annotations map[string]string `json:"annotations"`
+}
+
+func (r *OCIRuntime) Load(id string) (containerkit.ProcessDelegate, error) {
+	data, err := r.command("state", id).Output()
+	if err != nil {
+		return nil, err
+	}
+	var s state
+	if err := json.Unmarshal(data, &s); err != nil {
+		return nil, err
+	}
+	return newProcess(s.Pid)
+}
+
 func (r *OCIRuntime) command(args ...string) *exec.Cmd {
-	return exec.Command(r.name, append([]string{
+	baseArgs := append([]string{
 		"--root", r.root,
 		"--log", r.log,
-	}, args...)...)
+	}, r.args...)
+	return exec.Command(r.name, append(baseArgs, args...)...)
 }
 
 func newProcess(pid int) (*process, error) {