only compute delta on non-creating updates

plugin/pkg/admission/resourcequota/admission_test.go

@@ -295,8 +295,8 @@ func TestAdmitHandlesOldObjects(t *testing.T) {
 	indexer.Add(resourceQuota)
 
 	// old service was a load balancer, but updated version is a node port.
-	oldService := &api.Service{
-		ObjectMeta: api.ObjectMeta{Name: "service", Namespace: "test"},
+	existingService := &api.Service{
+		ObjectMeta: api.ObjectMeta{Name: "service", Namespace: "test", ResourceVersion: "1"},
 		Spec:       api.ServiceSpec{Type: api.ServiceTypeLoadBalancer},
 	}
 	newService := &api.Service{
@@ -306,7 +306,7 @@ func TestAdmitHandlesOldObjects(t *testing.T) {
 			Ports: []api.ServicePort{{Port: 1234}},
 		},
 	}
-	err := handler.Admit(admission.NewAttributesRecord(newService, oldService, api.Kind("Service").WithVersion("version"), newService.Namespace, newService.Name, api.Resource("services").WithVersion("version"), "", admission.Update, nil))
+	err := handler.Admit(admission.NewAttributesRecord(newService, existingService, api.Kind("Service").WithVersion("version"), newService.Namespace, newService.Name, api.Resource("services").WithVersion("version"), "", admission.Update, nil))
 	if err != nil {
 		t.Errorf("Unexpected error: %v", err)
 	}

plugin/pkg/admission/resourcequota/controller.go

@@ -369,9 +369,15 @@ func (e *quotaEvaluator) checkRequest(quotas []api.ResourceQuota, a admission.At
 		if prevItem == nil {
 			return nil, admission.NewForbidden(a, fmt.Errorf("unable to get previous usage since prior version of object was not found"))
 		}
+
+		// if we can definitively determine that this is not a case of "create on update",
+		// then charge based on the delta.  Otherwise, bill the maximum
+		metadata, err := meta.Accessor(prevItem)
+		if err == nil && len(metadata.GetResourceVersion()) > 0 {
 			prevUsage := evaluator.Usage(prevItem)
 			deltaUsage = quota.Subtract(deltaUsage, prevUsage)
 		}
+	}
 	if quota.IsZero(deltaUsage) {
 		return quotas, nil
 	}