snapshot/storage: namespace snapshot drivers

Signed-off-by: Stephen J Day <stephen.day@docker.com>

snapshot/storage/bolt.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 
 	"github.com/boltdb/bolt"
+	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/snapshot"
 	db "github.com/containerd/containerd/snapshot/storage/proto"
 	"github.com/gogo/protobuf/proto"
@@ -136,7 +137,7 @@ func CreateActive(ctx context.Context, key, parent string, readonly bool) (a Act
 			return snapshot.ErrSnapshotExist
 		}
 
-		id, err := bkt.NextSequence()
+		id, err := nextSequence(ctx)
 		if err != nil {
 			return errors.Wrap(err, "unable to get identifier")
 		}
@@ -309,28 +310,68 @@ func CommitActive(ctx context.Context, key, name string, usage snapshot.Usage) (
 	return
 }
 
+// nextSequence maintains the snapshot ids in the same space across namespaces
+// to avoid collisions on the filesystem, which is typically not namespace
+// aware. This will also be useful to ensure that snapshots can be used across
+// namespaces in the future, by projecting parent relationships into an
+// alternate namespace without fixing up identifiers.
+func nextSequence(ctx context.Context) (uint64, error) {
+	t, ok := ctx.Value(transactionKey{}).(*boltFileTransactor)
+	if !ok {
+		return 0, ErrNoTransaction
+	}
+
+	bkt := t.tx.Bucket(bucketKeyStorageVersion)
+	if bkt == nil {
+		return 0, errors.New("version bucket required for sequence")
+	}
+
+	return bkt.NextSequence()
+}
+
 func withBucket(ctx context.Context, fn func(context.Context, *bolt.Bucket, *bolt.Bucket) error) error {
+	namespace, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return err
+	}
 	t, ok := ctx.Value(transactionKey{}).(*boltFileTransactor)
 	if !ok {
 		return ErrNoTransaction
 	}
-	bkt := t.tx.Bucket(bucketKeyStorageVersion)
-	if bkt == nil {
+	nbkt := t.tx.Bucket(bucketKeyStorageVersion)
+	if nbkt == nil {
 		return errors.Wrap(snapshot.ErrSnapshotNotExist, "bucket does not exist")
 	}
+
+	bkt := nbkt.Bucket([]byte(namespace))
+	if bkt == nil {
+		return errors.Wrap(snapshot.ErrSnapshotNotExist, "namespace not available in snapshotter")
+	}
+
 	return fn(ctx, bkt.Bucket(bucketKeySnapshot), bkt.Bucket(bucketKeyParents))
 }
 
 func createBucketIfNotExists(ctx context.Context, fn func(context.Context, *bolt.Bucket, *bolt.Bucket) error) error {
+	namespace, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return err
+	}
+
 	t, ok := ctx.Value(transactionKey{}).(*boltFileTransactor)
 	if !ok {
 		return ErrNoTransaction
 	}
 
-	bkt, err := t.tx.CreateBucketIfNotExists(bucketKeyStorageVersion)
+	nbkt, err := t.tx.CreateBucketIfNotExists(bucketKeyStorageVersion)
 	if err != nil {
 		return errors.Wrap(err, "failed to create version bucket")
 	}
+
+	bkt, err := nbkt.CreateBucketIfNotExists([]byte(namespace))
+	if err != nil {
+		return err
+	}
+
 	sbkt, err := bkt.CreateBucketIfNotExists(bucketKeySnapshot)
 	if err != nil {
 		return errors.Wrap(err, "failed to create snapshots bucket")

snapshot/storage/metastore_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"testing"
 
+	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/snapshot"
 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
@@ -44,7 +45,7 @@ func MetaStoreSuite(t *testing.T, name string, meta func(root string) (*MetaStor
 // makeTest creates a testsuite with a writable transaction
 func makeTest(t *testing.T, name string, metaFn metaFactory, fn testFunc) func(t *testing.T) {
 	return func(t *testing.T) {
-		ctx := context.Background()
+		ctx := namespaces.WithNamespace(context.Background(), "testing-snapshot-metadata")
 		tmpDir, err := ioutil.TempDir("", "metastore-test-"+name+"-")
 		if err != nil {
 			t.Fatal(err)