DRA resourceslice controller: use preconditions for Delete

It's better to verify UID and ResourceVersion of the ResourceSlice that we want
to delete. If anything changed, the decision to remove it might not apply
anymore and we need to check again.

Author: pohly

staging/src/k8s.io/dynamic-resource-allocation/resourceslice/resourceslicecontroller.go

@@ -605,8 +605,22 @@ func (c *Controller) syncPool(ctx context.Context, poolName string) error {
 
 	// Remove stale slices.
 	for _, slice := range obsoleteSlices {
-		logger.V(5).Info("Deleting obsolete resource slice", "slice", klog.KObj(slice))
-		if err := c.kubeClient.ResourceV1alpha3().ResourceSlices().Delete(ctx, slice.Name, metav1.DeleteOptions{}); err != nil && !apierrors.IsNotFound(err) {
+		options := metav1.DeleteOptions{
+			Preconditions: &metav1.Preconditions{
+				UID:             &slice.UID,
+				ResourceVersion: &slice.ResourceVersion,
+			},
+		}
+		// It can happen that we sync again shortly after deleting a
+		// slice and before the slice gets removed from the informer
+		// cache. The MutationCache can't help here because it does not
+		// track pending deletes.
+		//
+		// If this happens, we get a "not found error" and nothing
+		// changes on the server. The only downside is the extra API
+		// call. This isn't as bad as extra creates.
+		logger.V(5).Info("Deleting obsolete resource slice", "slice", klog.KObj(slice), "deleteOptions", options)
+		if err := c.kubeClient.ResourceV1alpha3().ResourceSlices().Delete(ctx, slice.Name, options); err != nil && !apierrors.IsNotFound(err) {
 			return fmt.Errorf("delete resource slice: %w", err)
 		}
 	}