Skip finalizers for non-MCM nodes

pkg/util/provider/machinecontroller/node.go

@@ -61,6 +61,15 @@ func (c *controller) updateNode(oldObj, newObj any) {
 		return
 	}
 
+	// Do not process node updates if there is no associated machine
+	// In case of transient errors while fetching machine, do not retry
+	// as the update handler will be triggered again due to kubelet updates.
+	machine, err := c.getMachineFromNode(node.Name)
+	if err != nil {
+		klog.Errorf("unable to handle update event for node %q, couldn't fetch associated machine. Error: %v", node.Name, err)
+		return
+	}
+
 	// delete the machine if the node is deleted
 	if node.DeletionTimestamp != nil {
 		err := c.triggerMachineDeletion(context.Background(), node.Name)
@@ -69,18 +78,11 @@ func (c *controller) updateNode(oldObj, newObj any) {
 		}
 		return
 	}
-	// Check if finalizer was removed - re-add it
-	if c.hasNodeFinalizerBeenRemoved(oldNode, node, NodeFinalizerName) {
-		c.enqueueNodeAfter(node, time.Duration(machineutils.MediumRetry), fmt.Sprintf("MCM finalizer was removed from node %q, re-queuing", node.Name))
-		return
-	}
 
-	machine, err := c.getMachineFromNode(node.Name)
-	if err != nil {
-		klog.Errorf("unable to handle update event for node %q, couldn't fetch associated machine. Error: %v", node.Name, err)
+	if !HasFinalizer(node, NodeFinalizerName) {
+		c.enqueueNodeAfter(node, time.Duration(machineutils.MediumRetry), fmt.Sprintf("MCM finalizer missing from node %q, re-queuing", node.Name))
 		return
 	}
-
 	// to reconcile on addition/removal of essential taints in machine lifecycle, example - critical component taint
 	if addedOrRemovedEssentialTaints(oldNode, node, machineutils.EssentialTaints) {
 		c.enqueueMachine(machine, fmt.Sprintf("handling node UPDATE event. Atleast one of essential taints on node %q has changed", getNodeName(machine)))
@@ -145,6 +147,17 @@ func (c *controller) reconcileClusterNodeKey(key string) error {
 		return nil
 	}
 
+	// Ignore node updates without an associated machine. Retry only for errors other than errNoMachineMatch;
+	// transient fetch errors will be eventually requeued by the update handler due to kubelet updates.
+	if _, err := c.getMachineFromNode(node.Name); err != nil {
+		if errors.Is(err, errNoMachineMatch) {
+			klog.Errorf("ClusterNode %q: No machine found matching node, skipping adding finalizers", key)
+			return nil
+		}
+		klog.Errorf("ClusterNode %q: error fetching machine for node: %v", key, err)
+		return err
+	}
+
 	if node.DeletionTimestamp != nil {
 		err := c.triggerMachineDeletion(context.Background(), node.Name)
 		if err != nil {
@@ -271,10 +284,6 @@ func (c *controller) updateNodeFinalizers(ctx context.Context, node *corev1.Node
 	return nil
 }
 
-func (c *controller) hasNodeFinalizerBeenRemoved(oldNode, newNode *corev1.Node, finalizerName string) bool {
-	return HasFinalizer(oldNode, finalizerName) && !HasFinalizer(newNode, finalizerName)
-}
-
 // HasFinalizer checks if the given object has the specified finalizer.
 func HasFinalizer(o metav1.Object, finalizer string) bool {
 	return sets.NewString(o.GetFinalizers()...).Has(finalizer)