libcontainer: remove LinuxFactory

Since LinuxFactory has become the means to specify containers state
top directory (aka --root), and is only used by two methods (Create
and Load), it is easier to pass root to them directly.

Modify all the users and the docs accordingly.

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

libcontainer/README.md

@@ -40,18 +40,7 @@ func init() {
 }
 ```
 
-Then to create a container you first have to initialize an instance of a factory
-that will handle the creation and initialization for a container.
-
-```go
-factory, err := libcontainer.New("/var/lib/container")
-if err != nil {
-	logrus.Fatal(err)
-	return
-}
-```
-
-Once you have an instance of the factory created we can create a configuration
+Then to create a container you first have to create a configuration
 struct describing how the container is to be created. A sample would look similar to this:
 
 ```go
@@ -242,10 +231,11 @@ config := &configs.Config{
 }
 ```
 
-Once you have the configuration populated you can create a container:
+Once you have the configuration populated you can create a container
+with a specified ID under a specified state directory:
 
 ```go
-container, err := factory.Create("container-id", config)
+container, err := libcontainer.Create("/run/containers", "container-id", config)
 if err != nil {
 	logrus.Fatal(err)
 	return

libcontainer/cgroups/manager/new.go

@@ -55,10 +55,10 @@ func NewWithPaths(config *configs.Cgroup, paths map[string]string) (cgroups.Mana
 	return fs.NewManager(config, paths)
 }
 
-// getUnifiedPath is an implementation detail of libcontainer factory.
-// Historically, it saves cgroup paths as per-subsystem path map (as returned
-// by cm.GetPaths(""), but with v2 we only have one single unified path
-// (with "" as a key).
+// getUnifiedPath is an implementation detail of libcontainer.
+// Historically, libcontainer.Create saves cgroup paths as per-subsystem path
+// map (as returned by cm.GetPaths(""), but with v2 we only have one single
+// unified path (with "" as a key).
 //
 // This function converts from that map to string (using "" as a key),
 // and also checks that the map itself is sane.

libcontainer/factory_linux.go

@@ -27,35 +27,23 @@ const (
 
 var idRegex = regexp.MustCompile(`^[\w+-\.]+$`)
 
-// New returns a linux based container factory based in the root directory.
-func New(root string) (*LinuxFactory, error) {
-	if err := os.MkdirAll(root, 0o700); err != nil {
-		return nil, err
-	}
-	return &LinuxFactory{
-		Root: root,
-	}, nil
-}
-
-// LinuxFactory implements the default factory interface for linux based systems.
-type LinuxFactory struct {
-	// Root directory for the factory to store state.
-	Root string
-}
-
-// Create creates a new container with the given id and starts the initial
-// process inside it.
+// Create creates a new container with the given id inside a given state
+// directory (root), and starts the initial process inside it.
+//
+// The root is a state directory which many containers can share. It can be
+// used later to get the list of containers, or to get information about a
+// particular container (see Load).
 //
 // 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.
+// unique and non-existent for the given 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 == "" {
+func Create(root, id string, config *configs.Config) (Container, error) {
+	if root == "" {
 		return nil, errors.New("root not set")
 	}
 	if err := validateID(id); err != nil {
@@ -64,7 +52,10 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 	if err := validate.Validate(config); err != nil {
 		return nil, err
 	}
-	containerRoot, err := securejoin.SecureJoin(l.Root, id)
+	if err := os.MkdirAll(root, 0o700); err != nil {
+		return nil, err
+	}
+	containerRoot, err := securejoin.SecureJoin(root, id)
 	if err != nil {
 		return nil, err
 	}
@@ -108,7 +99,8 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 		return nil, errors.New("container's cgroup unexpectedly frozen")
 	}
 
-	if err := os.MkdirAll(containerRoot, 0o711); err != nil {
+	// Parent directory is already created above, so Mkdir is enough.
+	if err := os.Mkdir(containerRoot, 0o711); err != nil {
 		return nil, err
 	}
 	c := &linuxContainer{
@@ -122,18 +114,18 @@ 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 == "" {
+// Load takes a path to the state directory (root) and an id of an existing
+// container and returns the container information from the stateDir. This
+// presents a read only view of the container.
+func Load(root, id string) (Container, error) {
+	if root == "" {
 		return nil, errors.New("root not set")
 	}
 	// when load, we need to check id is valid or not.
 	if err := validateID(id); err != nil {
 		return nil, err
 	}
-	containerRoot, err := securejoin.SecureJoin(l.Root, id)
+	containerRoot, err := securejoin.SecureJoin(root, id)
 	if err != nil {
 		return nil, err
 	}

libcontainer/factory_linux_test.go

@@ -12,26 +12,9 @@ import (
 	"github.com/opencontainers/runtime-spec/specs-go"
 )
 
-func TestFactoryNew(t *testing.T) {
-	root := t.TempDir()
-	factory, err := New(root)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if factory == nil {
-		t.Fatal("factory should not be nil")
-	}
-	if factory.Root != root {
-		t.Fatalf("expected factory root to be %q but received %q", root, factory.Root)
-	}
-}
-
 func TestFactoryLoadNotExists(t *testing.T) {
-	factory, err := New(t.TempDir())
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = factory.Load("nocontainer")
+	stateDir := t.TempDir()
+	_, err := Load(stateDir, "nocontainer")
 	if err == nil {
 		t.Fatal("expected nil error loading non-existing container")
 	}
@@ -77,11 +60,7 @@ func TestFactoryLoadContainer(t *testing.T) {
 	if err := marshal(filepath.Join(root, id, stateFilename), expectedState); err != nil {
 		t.Fatal(err)
 	}
-	factory, err := New(root)
-	if err != nil {
-		t.Fatal(err)
-	}
-	container, err := factory.Load(id)
+	container, err := Load(root, id)
 	if err != nil {
 		t.Fatal(err)
 	}

libcontainer/integration/checkpoint_test.go

@@ -62,10 +62,9 @@ func testCheckpoint(t *testing.T, userns bool) {
 	}
 
 	config := newTemplateConfig(t, &tParam{userns: userns})
-	factory, err := libcontainer.New(t.TempDir())
-	ok(t, err)
+	stateDir := t.TempDir()
 
-	container, err := factory.Create("test", config)
+	container, err := libcontainer.Create(stateDir, "test", config)
 	ok(t, err)
 	defer destroyContainer(container)
 
@@ -143,7 +142,7 @@ func testCheckpoint(t *testing.T, userns bool) {
 	ok(t, err)
 
 	// reload the container
-	container, err = factory.Load("test")
+	container, err = libcontainer.Load(stateDir, "test")
 	ok(t, err)
 
 	restoreStdinR, restoreStdinW, err := os.Pipe()

libcontainer/integration/utils_test.go

@@ -169,11 +169,7 @@ func newContainer(t *testing.T, config *configs.Config) (libcontainer.Container,
 	name := strings.ReplaceAll(t.Name(), "/", "_") + strconv.FormatInt(-int64(time.Now().Nanosecond()), 35)
 	root := t.TempDir()
 
-	f, err := libcontainer.New(root)
-	if err != nil {
-		return nil, err
-	}
-	return f.Create(name, config)
+	return libcontainer.Create(root, name, config)
 }
 
 // runContainer runs the container with the specific config and arguments

libcontainer/restored_process.go

@@ -79,8 +79,8 @@ func (p *restoredProcess) forwardChildLogs() chan error {
 }
 
 // nonChildProcess represents a process where the calling process is not
-// the parent process.  This process is created when a factory loads a container from
-// a persisted state.
+// the parent process. This process is created when Load loads a container
+// from a persisted state.
 type nonChildProcess struct {
 	processPid       int
 	processStartTime uint64

list.go

@@ -121,11 +121,6 @@ func getContainers(context *cli.Context) ([]containerState, error) {
 		// Report other errors, including non-existent custom --root.
 		return nil, err
 	}
-	factory, err := libcontainer.New(root)
-	if err != nil {
-		return nil, err
-	}
-
 	var s []containerState
 	for _, item := range list {
 		if !item.IsDir() {
@@ -146,7 +141,7 @@ func getContainers(context *cli.Context) ([]containerState, error) {
 			owner.Name = fmt.Sprintf("#%d", uid)
 		}
 
-		container, err := factory.Load(item.Name())
+		container, err := libcontainer.Load(root, item.Name())
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "load container %s: %v\n", item.Name(), err)
 			continue

utils_linux.go

@@ -23,19 +23,15 @@ import (
 
 var errEmptyID = errors.New("container id cannot be empty")
 
-// getContainer returns the specified container instance by loading it from state
-// with the default factory.
+// getContainer returns the specified container instance by loading it from
+// a state directory (root).
 func getContainer(context *cli.Context) (libcontainer.Container, error) {
 	id := context.Args().First()
 	if id == "" {
 		return nil, errEmptyID
 	}
 	root := context.GlobalString("root")
-	factory, err := libcontainer.New(root)
-	if err != nil {
-		return nil, err
-	}
-	return factory.Load(id)
+	return libcontainer.Load(root, id)
 }
 
 func getDefaultImagePath() string {
@@ -185,11 +181,7 @@ func createContainer(context *cli.Context, id string, spec *specs.Spec) (libcont
 	}
 
 	root := context.GlobalString("root")
-	factory, err := libcontainer.New(root)
-	if err != nil {
-		return nil, err
-	}
-	return factory.Create(id, config)
+	return libcontainer.Create(root, id, config)
 }
 
 type runner struct {