Validate flavor image min ram when resize volume-backed instance

When resize instance, the flavors returned may not meet the image
minimum memory requirement, resizing instance ignores the minimum
memory limit of the image, which may cause the resizing be
successfully, but the instance fails to start because the memory is
too small to run the system.

Related-Bug: 2007968
Change-Id: I132e444eedc10b950a2fc9ed259cd6d9aa9bed65

nova/compute/api.py

@@ -4269,6 +4269,12 @@ class API:
             if volume_backed:
                 self._validate_flavor_image_numa_pci(
                     image, new_flavor, validate_pci=True)
+                # The server that image-backed already has the verification of
+                # image min_ram when calling _validate_flavor_image_nostatus.
+                # Here, the verification is added for the server that
+                # volume-backed.
+                if new_flavor['memory_mb'] < int(image.get('min_ram', 0)):
+                    raise exception.FlavorMemoryTooSmall()
             else:
                 self._validate_flavor_image_nostatus(
                     context, image, new_flavor, root_bdm=None,

nova/tests/functional/regressions/test_bug_2007968.py

@@ -13,6 +13,7 @@
 import fixtures
 
 from nova.tests.fixtures import libvirt as fakelibvirt
+from nova.tests.functional.api import client
 from nova.tests.functional.libvirt import base
 
 
@@ -56,5 +57,11 @@ class Bug2007968RegressionTest(base.ServersTestBase):
         # This can cause the instance for boot from volume to be allowed to
         # get to the resize verify status, but the instance's application runs
         # abnormally due to insufficient memory, and it may be killed by OOM.
-        server = self._resize_server(server, new_flavor)
-        self.assertEqual(server['status'], 'VERIFY_RESIZE')
+
+        # After the fix, compute api will directly raise FlavorMemoryTooSmall
+        # and will not continue the resize.
+        ex = self.assertRaises(client.OpenStackApiException,
+                               self._resize_server, server, new_flavor)
+        self.assertEqual(400, ex.response.status_code)
+        self.assertIn('Flavor\'s memory is too small for requested image.',
+                      ex.response.text)

nova/tests/unit/compute/test_api.py

@@ -2376,6 +2376,39 @@ class _ComputeAPIUnitTestMixIn(object):
         mock_resize.assert_not_called()
         mock_save.assert_not_called()
 
+    @mock.patch('nova.compute.utils.is_volume_backed_instance',
+                return_value=True)
+    @mock.patch('nova.servicegroup.api.API.service_is_up',
+                new=mock.Mock(return_value=True))
+    @mock.patch.object(objects.Instance, 'save')
+    @mock.patch.object(compute_api.API, '_record_action_start')
+    @mock.patch.object(quotas_obj.Quotas, 'limit_check_project_and_user')
+    @mock.patch.object(quotas_obj.Quotas, 'count_as_dict')
+    @mock.patch.object(flavors, 'get_flavor_by_flavor_id')
+    def test_resize_vol_backed_smaller_min_ram(self, mock_get_flavor,
+                                               mock_count, mock_limit,
+                                               mock_record, mock_save,
+                                               mock_is_vol_backed):
+        mock_resize = self.useFixture(fixtures.MockPatchObject(
+            self.compute_api.compute_task_api, 'resize_instance')).mock
+        # Resize down from 512 MB to 64 MB.
+        params = dict(image_ref='', system_metadata={'min_ram': 512})
+        fake_inst = self._create_instance_obj(params=params)
+        new_flavor = self._create_flavor(id=200, flavorid=200,
+                                         name='new_flavor', disabled=False,
+                                         memory_mb=64)
+        mock_get_flavor.return_value = new_flavor
+        self.assertRaises(exception.FlavorMemoryTooSmall,
+                          self.compute_api.resize, self.context,
+                          fake_inst, flavor_id=new_flavor.id)
+        mock_get_flavor.assert_called_once_with(200, read_deleted='no')
+        # Should never reach these.
+        mock_count.assert_not_called()
+        mock_limit.assert_not_called()
+        mock_record.assert_not_called()
+        mock_resize.assert_not_called()
+        mock_save.assert_not_called()
+
     @mock.patch('nova.servicegroup.api.API.service_is_up',
                 new=mock.Mock(return_value=True))
     @mock.patch.object(objects.Instance, 'save')