Fail backup if it already exists in object storage

Signed-off-by: Andy Goldstein <andy.goldstein@gmail.com>

pkg/plugin/framework/object_store_client.go

@@ -96,6 +96,21 @@ func (c *ObjectStoreGRPCClient) PutObject(bucket, key string, body io.Reader) er
 	}
 }
 
+// ObjectExists checks if there is an object with the given key in the object storage bucket.
+func (c *ObjectStoreGRPCClient) ObjectExists(bucket, key string) (bool, error) {
+	req := &proto.ObjectExistsRequest{
+		Bucket: bucket,
+		Key:    key,
+	}
+
+	res, err := c.grpcClient.ObjectExists(context.Background(), req)
+	if err != nil {
+		return false, err
+	}
+
+	return res.Exists, nil
+}
+
 // GetObject retrieves the object with the given key from the specified
 // bucket in object storage.
 func (c *ObjectStoreGRPCClient) GetObject(bucket, key string) (io.ReadCloser, error) {

pkg/plugin/framework/object_store_server.go

@@ -128,6 +128,27 @@ func (s *ObjectStoreGRPCServer) PutObject(stream proto.ObjectStore_PutObjectServ
 	return nil
 }
 
+// ObjectExists checks if there is an object with the given key in the object storage bucket.
+func (s *ObjectStoreGRPCServer) ObjectExists(ctx context.Context, req *proto.ObjectExistsRequest) (response *proto.ObjectExistsResponse, err error) {
+	defer func() {
+		if recoveredErr := handlePanic(recover()); recoveredErr != nil {
+			err = recoveredErr
+		}
+	}()
+
+	impl, err := s.getImpl(req.Plugin)
+	if err != nil {
+		return nil, newGRPCError(err)
+	}
+
+	exists, err := impl.ObjectExists(req.Bucket, req.Key)
+	if err != nil {
+		return nil, err
+	}
+
+	return &proto.ObjectExistsResponse{Exists: exists}, nil
+}
+
 // GetObject retrieves the object with the given key from the specified
 // bucket in object storage.
 func (s *ObjectStoreGRPCServer) GetObject(req *proto.GetObjectRequest, stream proto.ObjectStore_GetObjectServer) (err error) {