Update metadata plugin initialization

Updates metadata plugin to require content and
snapshotter plugins be loaded and initializes with
those plugins, keeping the metadata database structure
static after initialization. Service plugins now only
require metadata plugin access snapshotter or content
stores through metadata, which was already required
behavior of the services.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

differ/differ.go

@@ -25,19 +25,14 @@ func init() {
 		Type: plugin.DiffPlugin,
 		ID:   "walking",
 		Requires: []plugin.Type{
-			plugin.ContentPlugin,
 			plugin.MetadataPlugin,
 		},
 		Init: func(ic *plugin.InitContext) (interface{}, error) {
-			c, err := ic.Get(plugin.ContentPlugin)
-			if err != nil {
-				return nil, err
-			}
 			md, err := ic.Get(plugin.MetadataPlugin)
 			if err != nil {
 				return nil, err
 			}
-			return NewWalkingDiff(metadata.NewContentStore(md.(*metadata.DB), c.(content.Store)))
+			return NewWalkingDiff(md.(*metadata.DB).ContentStore())
 		},
 	})
 }

metadata/bolt.go

@@ -17,9 +17,14 @@ func WithTransactionContext(ctx context.Context, tx *bolt.Tx) context.Context {
 	return context.WithValue(ctx, transactionKey{}, tx)
 }
 
+type transactor interface {
+	View(fn func(*bolt.Tx) error) error
+	Update(fn func(*bolt.Tx) error) error
+}
+
 // view gets a bolt db transaction either from the context
 // or starts a new one with the provided bolt database.
-func view(ctx context.Context, db *DB, fn func(*bolt.Tx) error) error {
+func view(ctx context.Context, db transactor, fn func(*bolt.Tx) error) error {
 	tx, ok := ctx.Value(transactionKey{}).(*bolt.Tx)
 	if !ok {
 		return db.View(fn)
@@ -29,7 +34,7 @@ func view(ctx context.Context, db *DB, fn func(*bolt.Tx) error) error {
 
 // update gets a writable bolt db transaction either from the context
 // or starts a new one with the provided bolt database.
-func update(ctx context.Context, db *DB, fn func(*bolt.Tx) error) error {
+func update(ctx context.Context, db transactor, fn func(*bolt.Tx) error) error {
 	tx, ok := ctx.Value(transactionKey{}).(*bolt.Tx)
 	if !ok {
 		return db.Update(fn)

metadata/content.go

@@ -19,23 +19,16 @@ import (
 
 type contentStore struct {
 	content.Store
-	db *DB
+	db transactor
 }
 
-// NewContentStore returns a namespaced content store using an existing
+// newContentStore returns a namespaced content store using an existing
 // content store interface.
-func NewContentStore(db *DB, cs content.Store) content.Store {
+func newContentStore(db transactor, cs content.Store) content.Store {
-	db.storeL.Lock()
+	return &contentStore{
-	defer db.storeL.Unlock()
-
-	if db.cs == nil {
-		db.cs = &contentStore{
 		Store: cs,
 		db:    db,
 	}
-	}
-	return db.cs
-
 }
 
 func (cs *contentStore) Info(ctx context.Context, dgst digest.Digest) (content.Info, error) {
@@ -360,7 +353,7 @@ type namespacedWriter struct {
 	content.Writer
 	ref       string
 	namespace string
-	db        *DB
+	db        transactor
 }
 
 func (nw *namespacedWriter) Commit(ctx context.Context, size int64, expected digest.Digest, opts ...content.Opt) error {

metadata/content_test.go

@@ -23,7 +23,7 @@ func createContentStore(ctx context.Context, root string) (content.Store, func()
 		return nil, nil, err
 	}
 
-	return NewContentStore(NewDB(db), cs), func() error {
+	return NewDB(db, cs, nil).ContentStore(), func() error {
 		return db.Close()
 	}, nil
 }

metadata/db.go

@@ -1,26 +1,40 @@
 package metadata
 
 import (
-	"sync"
-
 	"github.com/boltdb/bolt"
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/snapshot"
 )
 
 type DB struct {
 	db *bolt.DB
-
+	ss map[string]snapshot.Snapshotter
-	storeL sync.Mutex
+	cs content.Store
-	ss     map[string]*snapshotter
-	cs     *contentStore
 }
 
-func NewDB(db *bolt.DB) *DB {
+func NewDB(db *bolt.DB, cs content.Store, ss map[string]snapshot.Snapshotter) *DB {
 	return &DB{
 		db: db,
-		ss: map[string]*snapshotter{},
+		ss: ss,
+		cs: cs,
 	}
 }
 
+func (m *DB) ContentStore() content.Store {
+	if m.cs == nil {
+		return nil
+	}
+	return newContentStore(m, m.cs)
+}
+
+func (m *DB) Snapshotter(name string) snapshot.Snapshotter {
+	sn, ok := m.ss[name]
+	if !ok {
+		return nil
+	}
+	return newSnapshotter(m, name, sn)
+}
+
 func (m *DB) View(fn func(*bolt.Tx) error) error {
 	return m.db.View(fn)
 }

metadata/snapshot.go

@@ -19,26 +19,17 @@ import (
 type snapshotter struct {
 	snapshot.Snapshotter
 	name string
-	db   *DB
+	db   transactor
 }
 
-// NewSnapshotter returns a new Snapshotter which namespaces the given snapshot
+// newSnapshotter returns a new Snapshotter which namespaces the given snapshot
-// using the provided name and metadata store.
+// using the provided name and database.
-func NewSnapshotter(db *DB, name string, sn snapshot.Snapshotter) snapshot.Snapshotter {
+func newSnapshotter(db transactor, name string, sn snapshot.Snapshotter) snapshot.Snapshotter {
-	db.storeL.Lock()
+	return &snapshotter{
-	defer db.storeL.Unlock()
-
-	ss, ok := db.ss[name]
-	if !ok {
-		ss = &snapshotter{
 		Snapshotter: sn,
 		name:        name,
 		db:          db,
 	}
-		db.ss[name] = ss
-	}
-
-	return ss
 }
 
 func createKey(id uint64, namespace, key string) string {
@@ -466,11 +457,7 @@ func (s *snapshotter) Remove(ctx context.Context, key string) error {
 			}
 		}
 
-		if err := bkt.DeleteBucket([]byte(key)); err != nil {
+		return bkt.DeleteBucket([]byte(key))
-			return err
-		}
-
-		return nil
 	})
 }
 

metadata/snapshot_test.go

@@ -13,7 +13,7 @@ import (
 	"github.com/containerd/containerd/testutil"
 )
 
-func newSnapshotter(ctx context.Context, root string) (snapshot.Snapshotter, func() error, error) {
+func newTestSnapshotter(ctx context.Context, root string) (snapshot.Snapshotter, func() error, error) {
 	naiveRoot := filepath.Join(root, "naive")
 	if err := os.Mkdir(naiveRoot, 0770); err != nil {
 		return nil, nil, err
@@ -28,7 +28,7 @@ func newSnapshotter(ctx context.Context, root string) (snapshot.Snapshotter, fun
 		return nil, nil, err
 	}
 
-	sn := NewSnapshotter(NewDB(db), "naive", snapshotter)
+	sn := NewDB(db, nil, map[string]snapshot.Snapshotter{"naive": snapshotter}).Snapshotter("naive")
 
 	return sn, func() error {
 		return db.Close()
@@ -38,5 +38,5 @@ func newSnapshotter(ctx context.Context, root string) (snapshot.Snapshotter, fun
 func TestMetadata(t *testing.T) {
 	// Snapshot tests require mounting, still requires root
 	testutil.RequiresRoot(t)
-	testsuite.SnapshotterSuite(t, "Metadata", newSnapshotter)
+	testsuite.SnapshotterSuite(t, "Metadata", newTestSnapshotter)
 }

server/server.go

@@ -12,19 +12,21 @@ import (
 
 	"github.com/boltdb/bolt"
 	containers "github.com/containerd/containerd/api/services/containers/v1"
-	content "github.com/containerd/containerd/api/services/content/v1"
+	contentapi "github.com/containerd/containerd/api/services/content/v1"
 	diff "github.com/containerd/containerd/api/services/diff/v1"
 	eventsapi "github.com/containerd/containerd/api/services/events/v1"
 	images "github.com/containerd/containerd/api/services/images/v1"
 	namespaces "github.com/containerd/containerd/api/services/namespaces/v1"
-	snapshot "github.com/containerd/containerd/api/services/snapshot/v1"
+	snapshotapi "github.com/containerd/containerd/api/services/snapshot/v1"
 	tasks "github.com/containerd/containerd/api/services/tasks/v1"
 	version "github.com/containerd/containerd/api/services/version/v1"
+	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/content/local"
 	"github.com/containerd/containerd/events"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/metadata"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/snapshot"
 	metrics "github.com/docker/go-metrics"
 	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
 	"golang.org/x/net/context"
@@ -176,15 +178,34 @@ func loadPlugins(config *Config) ([]*plugin.Registration, error) {
 	plugin.Register(&plugin.Registration{
 		Type: plugin.MetadataPlugin,
 		ID:   "bolt",
+		Requires: []plugin.Type{
+			plugin.ContentPlugin,
+			plugin.SnapshotPlugin,
+		},
 		Init: func(ic *plugin.InitContext) (interface{}, error) {
 			if err := os.MkdirAll(ic.Root, 0711); err != nil {
 				return nil, err
 			}
+			cs, err := ic.Get(plugin.ContentPlugin)
+			if err != nil {
+				return nil, err
+			}
+
+			rawSnapshotters, err := ic.GetAll(plugin.SnapshotPlugin)
+			if err != nil {
+				return nil, err
+			}
+
+			snapshotters := make(map[string]snapshot.Snapshotter)
+			for name, sn := range rawSnapshotters {
+				snapshotters[name] = sn.(snapshot.Snapshotter)
+			}
+
 			db, err := bolt.Open(filepath.Join(ic.Root, "meta.db"), 0644, nil)
 			if err != nil {
 				return nil, err
 			}
-			return metadata.NewDB(db), nil
+			return metadata.NewDB(db, cs.(content.Store), snapshotters), nil
 		},
 	})
 
@@ -204,7 +225,7 @@ func interceptor(
 		ctx = log.WithModule(ctx, "tasks")
 	case containers.ContainersServer:
 		ctx = log.WithModule(ctx, "containers")
-	case content.ContentServer:
+	case contentapi.ContentServer:
 		ctx = log.WithModule(ctx, "content")
 	case images.ImagesServer:
 		ctx = log.WithModule(ctx, "images")
@@ -212,7 +233,7 @@ func interceptor(
 		// No need to change the context
 	case version.VersionServer:
 		ctx = log.WithModule(ctx, "version")
-	case snapshot.SnapshotsServer:
+	case snapshotapi.SnapshotsServer:
 		ctx = log.WithModule(ctx, "snapshot")
 	case diff.DiffServer:
 		ctx = log.WithModule(ctx, "diff")

services/content/service.go

@@ -39,7 +39,6 @@ func init() {
 		Type: plugin.GRPCPlugin,
 		ID:   "content",
 		Requires: []plugin.Type{
-			plugin.ContentPlugin,
 			plugin.MetadataPlugin,
 		},
 		Init: NewService,
@@ -47,19 +46,13 @@ func init() {
 }
 
 func NewService(ic *plugin.InitContext) (interface{}, error) {
-	c, err := ic.Get(plugin.ContentPlugin)
-	if err != nil {
-		return nil, err
-	}
 	m, err := ic.Get(plugin.MetadataPlugin)
 	if err != nil {
 		return nil, err
 	}
 
-	cs := metadata.NewContentStore(m.(*metadata.DB), c.(content.Store))
-
 	return &Service{
-		store:     cs,
+		store:     m.(*metadata.DB).ContentStore(),
 		publisher: ic.Events,
 	}, nil
 }

services/snapshot/service.go

@@ -14,7 +14,6 @@ import (
 	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/snapshot"
 	protoempty "github.com/golang/protobuf/ptypes/empty"
-	"github.com/pkg/errors"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 )
@@ -24,7 +23,6 @@ func init() {
 		Type: plugin.GRPCPlugin,
 		ID:   "snapshots",
 		Requires: []plugin.Type{
-			plugin.SnapshotPlugin,
 			plugin.MetadataPlugin,
 		},
 		Init: newService,
@@ -34,30 +32,18 @@ func init() {
 var empty = &protoempty.Empty{}
 
 type service struct {
-	snapshotters map[string]snapshot.Snapshotter
+	db        *metadata.DB
 	publisher events.Publisher
 }
 
 func newService(ic *plugin.InitContext) (interface{}, error) {
-	rawSnapshotters, err := ic.GetAll(plugin.SnapshotPlugin)
-	if err != nil {
-		return nil, err
-	}
 	md, err := ic.Get(plugin.MetadataPlugin)
 	if err != nil {
 		return nil, err
 	}
-	snapshotters := make(map[string]snapshot.Snapshotter)
-	for name, sn := range rawSnapshotters {
-		snapshotters[name] = metadata.NewSnapshotter(md.(*metadata.DB), name, sn.(snapshot.Snapshotter))
-	}
-
-	if len(snapshotters) == 0 {
-		return nil, errors.Errorf("failed to create snapshotter service: no snapshotters loaded")
-	}
 
 	return &service{
-		snapshotters: snapshotters,
+		db:        md.(*metadata.DB),
 		publisher: ic.Events,
 	}, nil
 }
@@ -67,8 +53,8 @@ func (s *service) getSnapshotter(name string) (snapshot.Snapshotter, error) {
 		return nil, errdefs.ToGRPCf(errdefs.ErrInvalidArgument, "snapshotter argument missing")
 	}
 
-	sn, ok := s.snapshotters[name]
+	sn := s.db.Snapshotter(name)
-	if !ok {
+	if sn == nil {
 		return nil, errdefs.ToGRPCf(errdefs.ErrInvalidArgument, "snapshotter not loaded: %s", name)
 	}
 	return sn, nil

services/tasks/service.go

@@ -44,7 +44,6 @@ func init() {
 		Requires: []plugin.Type{
 			plugin.RuntimePlugin,
 			plugin.MetadataPlugin,
-			plugin.ContentPlugin,
 		},
 		Init: New,
 	})
@@ -59,11 +58,7 @@ func New(ic *plugin.InitContext) (interface{}, error) {
 	if err != nil {
 		return nil, err
 	}
-	ct, err := ic.Get(plugin.ContentPlugin)
+	cs := m.(*metadata.DB).ContentStore()
-	if err != nil {
-		return nil, err
-	}
-	cs := metadata.NewContentStore(m.(*metadata.DB), ct.(content.Store))
 	runtimes := make(map[string]runtime.Runtime)
 	for _, rr := range rt {
 		r := rr.(runtime.Runtime)