Do not fail to build a snapshot if base image is not found

This fixes bug #968066

Change-Id: I1959e4dd7cb19acef54f0e857f4d8b3d40985b77

nova/tests/test_libvirt.py

@@ -712,6 +712,40 @@ def test_snapshot_no_image_architecture(self):
         self.assertEquals(snapshot['status'], 'active')
         self.assertEquals(snapshot['name'], snapshot_name)
 
+    @test.skip_if(missing_libvirt(), "Test requires libvirt")
+    def test_snapshot_no_original_image(self):
+        self.flags(image_service='nova.image.fake.FakeImageService')
+
+        # Start test
+        image_service = utils.import_object(FLAGS.image_service)
+
+        # Assign a non-existent image
+        test_instance = copy.deepcopy(self.test_instance)
+        test_instance["image_ref"] = '661122aa-1234-dede-fefe-babababababa'
+
+        instance_ref = db.instance_create(self.context, test_instance)
+        properties = {'instance_id': instance_ref['id'],
+                      'user_id': str(self.context.user_id)}
+        snapshot_name = 'test-snap'
+        sent_meta = {'name': snapshot_name, 'is_public': False,
+                     'status': 'creating', 'properties': properties}
+        recv_meta = image_service.create(context, sent_meta)
+
+        self.mox.StubOutWithMock(connection.LibvirtConnection, '_conn')
+        connection.LibvirtConnection._conn.lookupByName = self.fake_lookup
+        self.mox.StubOutWithMock(connection.utils, 'execute')
+        connection.utils.execute = self.fake_execute
+
+        self.mox.ReplayAll()
+
+        conn = connection.LibvirtConnection(False)
+        conn.snapshot(self.context, instance_ref, recv_meta['id'])
+
+        snapshot = image_service.show(context, recv_meta['id'])
+        self.assertEquals(snapshot['properties']['image_state'], 'available')
+        self.assertEquals(snapshot['status'], 'active')
+        self.assertEquals(snapshot['name'], snapshot_name)
+
     def test_attach_invalid_volume_type(self):
         self.create_fake_libvirt_mock()
         connection.LibvirtConnection._conn.lookupByName = self.fake_lookup

nova/virt/libvirt/connection.py

@@ -619,7 +619,11 @@ def snapshot(self, context, instance, image_href):
 
         (image_service, image_id) = nova.image.get_image_service(
             context, instance['image_ref'])
-        base = image_service.show(context, image_id)
+        try:
+            base = image_service.show(context, image_id)
+        except exception.ImageNotFound:
+            base = {}
+
         _image_service = nova.image.get_image_service(context, image_href)
         snapshot_image_service, snapshot_image_id = _image_service
         snapshot = snapshot_image_service.show(context, snapshot_image_id)
@@ -635,7 +639,7 @@ def snapshot(self, context, instance, image_href):
                                    'ramdisk_id': instance['ramdisk_id'],
                                    }
                     }
-        if 'architecture' in base['properties']:
+        if 'architecture' in base.get('properties', {}):
             arch = base['properties']['architecture']
             metadata['properties']['architecture'] = arch