libct: remove Factory interface

The only implementation is LinuxFactory, let's use this directly.

Move the piece of documentation about Create from removed factory.go to
the factory_linux.go.

The LinuxFactory is to be removed later.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/factory.go

@@ -1,30 +0,0 @@
-package libcontainer
-
-import (
-	"github.com/opencontainers/runc/libcontainer/configs"
-)
-
-type Factory interface {
-	// Creates a new container with the given id and starts the initial process inside it.
-	// id must be a string containing only letters, digits and underscores and must contain
-	// between 1 and 1024 characters, inclusive.
-	//
-	// The id must not already be in use by an existing container. Containers created using
-	// a factory with the same path (and filesystem) must have distinct ids.
-	//
-	// Returns the new container with a running process.
-	//
-	// On error, any partially created container parts are cleaned up (the operation is atomic).
-	Create(id string, config *configs.Config) (Container, error)
-
-	// Load takes an ID for an existing container and returns the container information
-	// from the state.  This presents a read only view of the container.
-	Load(id string) (Container, error)
-
-	// StartInitialization is an internal API to libcontainer used during the reexec of the
-	// container.
-	StartInitialization() error
-
-	// Type returns info string about factory type (e.g. lxc, libcontainer...)
-	Type() string
-}

libcontainer/factory_linux.go

@@ -28,7 +28,7 @@ const (
 var idRegex = regexp.MustCompile(`^[\w+-\.]+$`)
 
 // New returns a linux based container factory based in the root directory.
-func New(root string) (Factory, error) {
+func New(root string) (*LinuxFactory, error) {
 	if root != "" {
 		if err := os.MkdirAll(root, 0o700); err != nil {
 			return nil, err
@@ -45,6 +45,17 @@ type LinuxFactory struct {
 	Root string
 }
 
+// Create creates a new container with the given id and starts the initial
+// process inside it.
+//
+// The id must not be empty and consists of only the following characters:
+// ASCII letters, digits, underscore, plus, minus, period. The id must be
+// unique and non-existent for the factory with  same root path.
+//
+// Returns the new container with a running process.
+//
+// On error, any partially created container parts are cleaned up (the
+// operation is atomic).
 func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, error) {
 	if l.Root == "" {
 		return nil, errors.New("root not set")
@@ -113,6 +124,9 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 	return c, nil
 }
 
+// Load takes an ID for an existing container and returns the container
+// information from the state. This presents a read only view of the
+// container.
 func (l *LinuxFactory) Load(id string) (Container, error) {
 	if l.Root == "" {
 		return nil, errors.New("root not set")
@@ -155,10 +169,6 @@ func (l *LinuxFactory) Load(id string) (Container, error) {
 	return c, nil
 }
 
-func (l *LinuxFactory) Type() string {
-	return "libcontainer"
-}
-
 // StartInitialization loads a container by opening the pipe fd from the parent to read the configuration and state
 // This is a low level implementation detail of the reexec and should not be consumed externally
 func (l *LinuxFactory) StartInitialization() (err error) {

libcontainer/factory_linux_test.go

@@ -21,16 +21,8 @@ func TestFactoryNew(t *testing.T) {
 	if factory == nil {
 		t.Fatal("factory should not be nil")
 	}
-	lfactory, ok := factory.(*LinuxFactory)
+	if factory.Root != root {
-	if !ok {
+		t.Fatalf("expected factory root to be %q but received %q", root, factory.Root)
-		t.Fatal("expected linux factory returned on linux based systems")
-	}
-	if lfactory.Root != root {
-		t.Fatalf("expected factory root to be %q but received %q", root, lfactory.Root)
-	}
-
-	if factory.Type() != "libcontainer" {
-		t.Fatalf("unexpected factory type: %q, expected %q", factory.Type(), "libcontainer")
 	}
 }