rbd: implement Manager.GetVolumeGroupSnapshotByID

The GetVolumeGroupSnapshotByID function makes it possible to get a
VolumeGroupSnapshot object from the Manager by passing a request-id.
This makes it simple for the Group Controller Server to check if a
VolumeGroupSnapshot already exists, so it is not needed to try and
re-create an existing one.

Signed-off-by: Niels de Vos <ndevos@ibm.com>

internal/rbd/manager.go

@@ -320,6 +320,23 @@ func (mgr *rbdManager) CreateVolumeGroup(ctx context.Context, name string) (type
 	return vg, nil
 }
 
+func (mgr *rbdManager) GetVolumeGroupSnapshotByID(
+	ctx context.Context,
+	id string,
+) (types.VolumeGroupSnapshot, error) {
+	creds, err := mgr.getCredentials()
+	if err != nil {
+		return nil, err
+	}
+
+	vgs, err := rbd_group.GetVolumeGroupSnapshot(ctx, id, mgr.csiID, creds, mgr)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get volume group with id %q: %w", id, err)
+	}
+
+	return vgs, nil
+}
+
 func (mgr *rbdManager) CreateVolumeGroupSnapshot(
 	ctx context.Context,
 	vg types.VolumeGroup,

internal/rbd/types/manager.go

@@ -53,6 +53,10 @@ type Manager interface {
 	// and records details about it in the journal.
 	CreateVolumeGroup(ctx context.Context, name string) (VolumeGroup, error)
 
+	// GetVolumeGroupSnapshotByID resolves the VolumeGroupSnapshot from the
+	// CSI id/handle.
+	GetVolumeGroupSnapshotByID(ctx context.Context, id string) (VolumeGroupSnapshot, error)
+
 	// CreateVolumeGroupSnapshot instructs the Manager to create a
 	// VolumeGroupSnapshot from the VolumeGroup. All snapshots in the
 	// returned VolumeGroupSnapshot have been taken while I/O on the