Ignore update request when nothing has changed in object.

In api client library, do not send update to server if none of the
attributes were updated. In api server, ignore PUTs when there is
no body or empty body.

Change-Id: Ia060380abb737c4ed7c869af15e23375f99fff41
Closes-Bug: #1502237

src/api-lib/vnc_api.py

@@ -376,13 +376,17 @@ def _object_update(self, res_type, obj):
         if not obj.uuid:
             obj.uuid = self.fq_name_to_id(res_type, obj.get_fq_name())
 
-        # Ignore fields with None value in json representation
-        json_param = json.dumps(obj, default=self._obj_serializer)
-        json_body = '{"%s":%s}' %(res_type, json_param)
+        # Generate PUT on object only if some attr was modified
+        content = None
+        if obj.get_pending_updates():
+            # Ignore fields with None value in json representation
+            json_param = json.dumps(obj, default=self._obj_serializer)
+            json_body = '{"%s":%s}' %(res_type, json_param)
+
+            id = obj.uuid
+            uri = obj_cls.resource_uri_base[res_type] + '/' + id
+            content = self._request_server(rest.OP_PUT, uri, data=json_body)
 
-        id = obj.uuid
-        uri = obj_cls.resource_uri_base[res_type] + '/' + id
-        content = self._request_server(rest.OP_PUT, uri, data=json_body)
         for ref_name in obj._pending_ref_updates:
              ref_orig = set([(x.get('uuid'),
                              tuple(x.get('to', [])), x.get('attr'))

src/config/api-server/tests/test_crud_basic.py

@@ -1614,6 +1614,26 @@ def test_vmi_links_to_native_ri(self):
         logger.info("...link to Native RI done.")
     # end test_vmi_links_to_native_ri
 
+    def test_nop_on_empty_body_update(self):
+        # library api test
+        vn_fq_name = VirtualNetwork().fq_name
+        vn_obj = self._vnc_lib.virtual_network_read(fq_name=vn_fq_name)
+        mod_time = vn_obj.id_perms.last_modified
+        resp = self._vnc_lib.virtual_network_update(vn_obj)
+        self.assertIsNone(resp)
+        vn_obj = self._vnc_lib.virtual_network_read(fq_name=vn_fq_name)
+        self.assertEqual(mod_time, vn_obj.id_perms.last_modified)
+
+        # rest api test
+        listen_ip = self._api_server_ip
+        listen_port = self._api_server._args.listen_port
+        url = 'http://%s:%s/virtual-network/%s' %(
+            listen_ip, listen_port, vn_obj.uuid)
+        resp = requests.put(url)
+        self.assertEqual(resp.status_code, 200)
+        self.assertEqual(resp.text, '')
+    # end test_nop_on_empty_body_update
+
 # end class TestVncCfgApiServer
 
 class TestVncCfgApiServerRequests(test_case.ApiServerTestCase):

src/config/api-server/vnc_cfg_api_server.py

@@ -556,6 +556,13 @@ def http_resource_read(self, resource_type, id):
     def http_resource_update(self, resource_type, id):
         r_class = self.get_resource_class(resource_type)
         obj_type = resource_type.replace('-', '_')
+        # Early return if there is no body or an empty body
+        request = get_request()
+        if (not hasattr(request, 'json') or
+            not request.json or
+            not request.json[resource_type]):
+            return
+
         obj_dict = get_request().json[resource_type]
         try:
             self._extension_mgrs['resourceApi'].map_method(