metadata: add content lease on existing content

When a writer is requested for an object that already
exists, add that object to the provided any lease to prevent
other operations from affecting the current lease's use of
that content.

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

metadata/content_test.go

@@ -1,6 +1,7 @@
 package metadata
 
 import (
+	"bytes"
 	"context"
 	"path/filepath"
 	"testing"
@@ -9,6 +10,11 @@ import (
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/content/local"
 	"github.com/containerd/containerd/content/testsuite"
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/leases"
+	"github.com/containerd/containerd/namespaces"
+	digest "github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
 )
 
 func createContentStore(ctx context.Context, root string) (content.Store, func() error, error) {
@@ -31,3 +37,76 @@ func createContentStore(ctx context.Context, root string) (content.Store, func()
 func TestContent(t *testing.T) {
 	testsuite.ContentSuite(t, "metadata", createContentStore)
 }
+
+func TestContentLeased(t *testing.T) {
+	ctx, db, cancel := testDB(t)
+	defer cancel()
+
+	cs := db.ContentStore()
+
+	blob := []byte("any content")
+	expected := digest.FromBytes(blob)
+
+	lctx, _, err := createLease(ctx, db, "lease-1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := content.WriteBlob(lctx, cs, "test-1", bytes.NewReader(blob), int64(len(blob)), expected); err != nil {
+		t.Fatal(err)
+	}
+	if err := checkContentLeased(lctx, db, expected); err != nil {
+		t.Fatal("lease checked failed:", err)
+	}
+
+	lctx, _, err = createLease(ctx, db, "lease-2")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := cs.Writer(lctx, "test-2", int64(len(blob)), expected); err == nil {
+		t.Fatal("expected already exist error")
+	} else if !errdefs.IsAlreadyExists(err) {
+		t.Fatal(err)
+	}
+	if err := checkContentLeased(lctx, db, expected); err != nil {
+		t.Fatal("lease checked failed:", err)
+	}
+}
+
+func createLease(ctx context.Context, db *DB, name string) (context.Context, func() error, error) {
+	if err := db.Update(func(tx *bolt.Tx) error {
+		_, err := NewLeaseManager(tx).Create(ctx, name, nil)
+		return err
+	}); err != nil {
+		return nil, nil, err
+	}
+	return leases.WithLease(ctx, name), func() error {
+		return db.Update(func(tx *bolt.Tx) error {
+			return NewLeaseManager(tx).Delete(ctx, name)
+		})
+	}, nil
+}
+
+func checkContentLeased(ctx context.Context, db *DB, dgst digest.Digest) error {
+	ns, ok := namespaces.Namespace(ctx)
+	if !ok {
+		return errors.New("no namespace in context")
+	}
+	lease, ok := leases.Lease(ctx)
+	if !ok {
+		return errors.New("no lease in context")
+	}
+
+	return db.View(func(tx *bolt.Tx) error {
+		bkt := getBucket(tx, bucketKeyVersion, []byte(ns), bucketKeyObjectLeases, []byte(lease), bucketKeyObjectContent)
+		if bkt == nil {
+			return errors.Wrapf(errdefs.ErrNotFound, "bucket not found", lease)
+		}
+		v := bkt.Get([]byte(dgst.String()))
+		if v == nil {
+			return errors.Wrap(errdefs.ErrNotFound, "object not leased")
+		}
+
+		return nil
+	})
+}