Fix creation empty file if exception on backup

Change-Id: I237ed62003c811a9844c4078dfce89ba715810a7

octane/commands/backup.py

@@ -13,7 +13,9 @@
 import contextlib
 import logging
 import os
+import shutil
 import tarfile
+import tempfile
 
 from cliff import command
 
@@ -28,10 +30,18 @@ def backup(path_to_backup, archivators):
         ext = ext[1:]
     else:
         ext = ""
-    tar_obj = tarfile.open(path_to_backup, "w|{0}".format(ext))
-    with contextlib.closing(tar_obj) as archive:
-        for manager in archivators:
-            manager(archive).backup()
+    abs_path_to_backup = os.path.abspath(path_to_backup)
+    prefix = ".{0}.".format(os.path.basename(abs_path_to_backup))
+    dirname = os.path.dirname(abs_path_to_backup)
+    with tempfile.NamedTemporaryFile(dir=dirname, prefix=prefix) as temp:
+        tar_obj = tarfile.open(fileobj=temp, mode="w|{0}".format(ext))
+        with contextlib.closing(tar_obj) as archive:
+            for manager in archivators:
+                manager(archive).backup()
+            if not archive.getmembers():
+                raise Exception("Nothing to backup")
+        shutil.move(temp.name, abs_path_to_backup)
+        temp.delete = False
 
 
 class BaseBackupCommand(command.Command):

octane/tests/test_backup.py

@@ -9,6 +9,7 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations
 # under the License.
+
 import pytest
 import sys
 
@@ -43,13 +44,34 @@ def test_parser_empty(mocker, octane_app, cmd, archivators, path):
     ("path.bz2", "w|bz2"),
     ("path.hz2", "w|"),
 ])
-def test_backup_admin_node_backup_file(mocker, path, mode):
+@pytest.mark.parametrize("empty", [True, False])
+def test_backup_admin_node_backup_file(mocker, path, mode, empty):
     manager = mocker.Mock()
     tar_obj = mocker.patch("tarfile.open")
-    backup.backup(path, [manager])
+    if empty:
+        tar_obj.return_value.getmembers.return_value = []
+    tmp_file = mocker.patch("tempfile.NamedTemporaryFile")
+    tmp_file.return_value.__enter__.return_value = tmp_file
+    move_mock = mocker.patch("shutil.move")
+    dir_path = "/abs"
+    abs_path = "{0}/{1}".format(dir_path, path)
+    os_abs_path_mock = mocker.patch("os.path.abspath", return_value=abs_path)
+    if empty:
+        with pytest.raises(Exception) as exc:
+            backup.backup(path, [manager])
+        assert "Nothing to backup" == exc.value.message
+    else:
+        backup.backup(path, [manager])
+    os_abs_path_mock.assert_called_once_with(path)
     manager.assert_called_once_with(tar_obj.return_value)
     manager.return_value.backup.assert_called_once_with()
+    tmp_file.assert_called_once_with(dir=dir_path, prefix=".{0}.".format(path))
     if path is not None:
-        tar_obj.assert_called_once_with(path, mode)
+        tar_obj.assert_called_once_with(fileobj=tmp_file, mode=mode)
+        if empty:
+            assert not move_mock.called
+        else:
+            move_mock.assert_called_once_with(tmp_file.name, abs_path)
     else:
         tar_obj.assert_called_once_with(fileobj=sys.stdout, mode=mode)
+        assert not move_mock.called