Interface: introduce status to runtime container

Signed-off-by: Hu Keping <hukeping@huawei.com>

runtime/container.go

@@ -52,6 +52,9 @@ type Container interface {
 	OOM() (OOM, error)
 	// UpdateResource updates the containers resources to new values
 	UpdateResources(*Resource) error
+
+	// Status return the current status of the container.
+	Status() (State, error)
 }
 
 type OOM interface {

runtime/container_linux.go

@@ -284,6 +284,11 @@ func (c *container) Stats() (*Stat, error) {
 	}, nil
 }
 
+// Status implements the runtime Container interface.
+func (c *container) Status() (State, error) {
+	return "running", nil
+}
+
 func (c *container) OOM() (OOM, error) {
 	container, err := c.getLibctContainer()
 	if err != nil {

runtime/container_windows.go

@@ -61,6 +61,11 @@ func (c *container) Stats() (*Stat, error) {
 	return nil, errors.New("Stats not yet implemented on Windows")
 }
 
+// Status implements the runtime Container interface.
+func (c *container) Status() (State, error) {
+	return "", errors.New("Status not yet implemented on Windows")
+}
+
 func (c *container) OOM() (OOM, error) {
 	return nil, errors.New("OOM not yet implemented on Windows")
 }