execution: add shim runtime

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

execution/statedir.go

@@ -4,32 +4,46 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+
+	"github.com/pkg/errors"
 )
 
 const processesDirName = "processes"
 
 type StateDir string
 
+func LoadStateDir(root, id string) (StateDir, error) {
+	path := filepath.Join(root, id)
+	if _, err := os.Stat(path); err != nil {
+		return "", errors.Wrap(err, "could not find container statedir")
+	}
+	return StateDir(path), nil
+}
+
 func NewStateDir(root, id string) (StateDir, error) {
 	path := filepath.Join(root, id)
 	if err := os.Mkdir(path, 0700); err != nil {
-		return "", err
+		return "", errors.Wrap(err, "could not create container statedir")
 	}
 	if err := os.Mkdir(StateDir(path).processesDir(), 0700); err != nil {
 		os.RemoveAll(path)
-		return "", err
+		return "", errors.Wrap(err, "could not create processes statedir")
 	}
 	return StateDir(path), nil
 }
 
 func (s StateDir) Delete() error {
-	return os.RemoveAll(string(s))
+	err := os.RemoveAll(string(s))
+	if err != nil {
+		return errors.Wrapf(err, "failed to remove statedir %s", string(s))
+	}
+	return nil
 }
 
 func (s StateDir) NewProcess(id string) (dir string, err error) {
 	dir = filepath.Join(s.processesDir(), id)
 	if err = os.Mkdir(dir, 0700); err != nil {
-		return "", err
+		return "", errors.Wrap(err, "could not create process statedir")
 	}
 
 	return dir, nil
@@ -40,14 +54,18 @@ func (s StateDir) ProcessDir(id string) string {
 }
 
 func (s StateDir) DeleteProcess(id string) error {
-	return os.RemoveAll(filepath.Join(s.processesDir(), id))
+	err := os.RemoveAll(filepath.Join(s.processesDir(), id))
+	if err != nil {
+		return errors.Wrapf(err, "failed to remove process %d statedir", id)
+	}
+	return nil
 }
 
 func (s StateDir) Processes() ([]string, error) {
 	procsDir := s.processesDir()
 	dirs, err := ioutil.ReadDir(procsDir)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrap(err, "could not list processes statedir")
 	}
 
 	paths := make([]string, 0)