Merge pull request #44 from crosbymichael/container-migration

Container and Image migration for aufs

graphdriver/aufs/aufs.go

@@ -95,18 +95,27 @@ func supportsAufs() error {
 	return fmt.Errorf("AUFS was not found in /proc/filesystems")
 }
 
-func (a *AufsDriver) rootPath() string {
+func (a AufsDriver) rootPath() string {
 	return a.root
 }
 
-func (a *AufsDriver) String() string {
+func (AufsDriver) String() string {
 	return "aufs"
 }
 
-func (d *AufsDriver) Status() [][2]string {
+func (AufsDriver) Status() [][2]string {
 	return nil
 }
 
+// Exists returns true if the given id is registered with
+// this driver
+func (a AufsDriver) Exists(id string) bool {
+	if _, err := os.Lstat(path.Join(a.rootPath(), "layers", id)); err != nil {
+		return false
+	}
+	return true
+}
+
 // Three folders are created for each id
 // mnt, layers, and diff
 func (a *AufsDriver) Create(id, parent string) error {

graphdriver/aufs/migrate.go

@@ -0,0 +1,183 @@
+package aufs
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+type metadata struct {
+	ID       string `json:"id"`
+	ParentID string `json:"parent,omitempty"`
+	Image    string `json:"Image,omitempty"`
+
+	parent *metadata
+}
+
+func pathExists(pth string) bool {
+	if _, err := os.Stat(pth); err != nil {
+		return false
+	}
+	return true
+}
+
+// Migrate existing images and containers from docker < 0.7.x
+//
+// The format pre 0.7 is for docker to store the metadata and filesystem
+// content in the same directory.  For the migration to work we need to move Image layer
+// data from /var/lib/docker/graph/<id>/layers to the diff of the registered id.
+//
+// Next we need to migrate the container's rw layer to diff of the driver.  After the
+// contents are migrated we need to register the image and container ids with the
+// driver.
+//
+// For the migration we try to move the folder containing the layer files, if that
+// fails because the data is currently mounted we will fallback to creating a
+// symlink.
+func (a *AufsDriver) Migrate(pth string, setupInit func(p string) error) error {
+	if pathExists(path.Join(pth, "graph")) {
+		if err := a.migrateImages(path.Join(pth, "graph")); err != nil {
+			return err
+		}
+		return a.migrateContainers(path.Join(pth, "containers"), setupInit)
+	}
+	return nil
+}
+
+func (a *AufsDriver) migrateContainers(pth string, setupInit func(p string) error) error {
+	fis, err := ioutil.ReadDir(pth)
+	if err != nil {
+		return err
+	}
+
+	for _, fi := range fis {
+		if id := fi.Name(); fi.IsDir() && pathExists(path.Join(pth, id, "rw")) {
+			if err := tryRelocate(path.Join(pth, id, "rw"), path.Join(a.rootPath(), "diff", id)); err != nil {
+				return err
+			}
+
+			if !a.Exists(id) {
+
+				metadata, err := loadMetadata(path.Join(pth, id, "config.json"))
+				if err != nil {
+					return err
+				}
+
+				initID := fmt.Sprintf("%s-init", id)
+				if err := a.Create(initID, metadata.Image); err != nil {
+					return err
+				}
+
+				initPath, err := a.Get(initID)
+				if err != nil {
+					return err
+				}
+				// setup init layer
+				if err := setupInit(initPath); err != nil {
+					return err
+				}
+
+				if err := a.Create(id, initID); err != nil {
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}
+
+func (a *AufsDriver) migrateImages(pth string) error {
+	fis, err := ioutil.ReadDir(pth)
+	if err != nil {
+		return err
+	}
+	var (
+		m       = make(map[string]*metadata)
+		current *metadata
+		exists  bool
+	)
+
+	for _, fi := range fis {
+		if id := fi.Name(); fi.IsDir() && pathExists(path.Join(pth, id, "layer")) {
+			if current, exists = m[id]; !exists {
+				current, err = loadMetadata(path.Join(pth, id, "json"))
+				if err != nil {
+					return err
+				}
+				m[id] = current
+			}
+		}
+	}
+
+	for _, v := range m {
+		v.parent = m[v.ParentID]
+	}
+
+	migrated := make(map[string]bool)
+	for _, v := range m {
+		if err := a.migrateImage(v, pth, migrated); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (a *AufsDriver) migrateImage(m *metadata, pth string, migrated map[string]bool) error {
+	if !migrated[m.ID] {
+		if m.parent != nil {
+			a.migrateImage(m.parent, pth, migrated)
+		}
+		if err := tryRelocate(path.Join(pth, m.ID, "layer"), path.Join(a.rootPath(), "diff", m.ID)); err != nil {
+			return err
+		}
+		if !a.Exists(m.ID) {
+			if err := a.Create(m.ID, m.ParentID); err != nil {
+				return err
+			}
+		}
+		migrated[m.ID] = true
+	}
+	return nil
+}
+
+// tryRelocate will try to rename the old path to the new pack and if
+// the operation fails, it will fallback to a symlink
+func tryRelocate(oldPath, newPath string) error {
+	s, err := os.Lstat(newPath)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	// If the destination is a symlink then we already tried to relocate once before
+	// and it failed so we delete it and try to remove
+	if s != nil && s.Mode()&os.ModeSymlink == os.ModeSymlink {
+		if err := os.RemoveAll(newPath); err != nil {
+			return err
+		}
+	}
+	if err := os.Rename(oldPath, newPath); err != nil {
+		if sErr := os.Symlink(oldPath, newPath); sErr != nil {
+			return fmt.Errorf("Unable to relocate %s to %s: Rename err %s Symlink err %s", oldPath, newPath, err, sErr)
+		}
+	}
+	return nil
+}
+
+func loadMetadata(pth string) (*metadata, error) {
+	f, err := os.Open(pth)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	var (
+		out = &metadata{}
+		dec = json.NewDecoder(f)
+	)
+
+	if err := dec.Decode(out); err != nil {
+		return nil, err
+	}
+	return out, nil
+}

runtime.go

@@ -8,7 +8,7 @@ import (
 	"github.com/dotcloud/docker/archive"
 	"github.com/dotcloud/docker/graphdb"
 	"github.com/dotcloud/docker/graphdriver"
-	_ "github.com/dotcloud/docker/graphdriver/aufs"
+	"github.com/dotcloud/docker/graphdriver/aufs"
 	_ "github.com/dotcloud/docker/graphdriver/devmapper"
 	_ "github.com/dotcloud/docker/graphdriver/dummy"
 	"github.com/dotcloud/docker/utils"
@@ -629,6 +629,12 @@ func NewRuntimeFromDirectory(config *DaemonConfig) (*Runtime, error) {
 		return nil, err
 	}
 
+	if ad, ok := driver.(*aufs.AufsDriver); ok {
+		if err := ad.Migrate(config.Root, setupInitLayer); err != nil {
+			return nil, err
+		}
+	}
+
 	if err := linkLxcStart(config.Root); err != nil {
 		return nil, err
 	}