From 1dca9bc6ed1ebe815a22618c6a97fb6cbf8a3627 Mon Sep 17 00:00:00 2001
From: Jayesh Srivastava <jayesh0200@gmail.com>
Date: Mon, 23 Jun 2025 22:21:57 +0530
Subject: [PATCH] Fix MachinePool nodeRef UID mismatch after K8s upgrade

---
 .../machinepool_controller_noderef.go         | 29 +++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/exp/internal/controllers/machinepool_controller_noderef.go b/exp/internal/controllers/machinepool_controller_noderef.go
index 35d37cda44dd..f025af5b055f 100644
--- a/exp/internal/controllers/machinepool_controller_noderef.go
+++ b/exp/internal/controllers/machinepool_controller_noderef.go
@@ -70,8 +70,33 @@ func (r *MachinePoolReconciler) reconcileNodeRefs(ctx context.Context, s *scope)
 		readyReplicas = mp.Status.Deprecated.V1Beta1.ReadyReplicas
 	}
 	if ptr.Deref(mp.Status.Replicas, 0) == readyReplicas && len(mp.Status.NodeRefs) == int(readyReplicas) {
-		v1beta1conditions.MarkTrue(mp, clusterv1.ReplicasReadyV1Beta1Condition)
-		return ctrl.Result{}, nil
+		// Validate that the UIDs in NodeRefs are still valid
+		if s.nodeRefMap != nil {
+			// Create a name-to-node mapping for efficient lookup
+			nodeNameMap := make(map[string]*corev1.Node)
+			for _, node := range s.nodeRefMap {
+				nodeNameMap[node.Name] = node
+			}
+
+			validNodeRefs := true
+			for _, nodeRef := range mp.Status.NodeRefs {
+				foundNode, exists := nodeNameMap[nodeRef.Name]
+
+				// If node not found or UID doesn't match, mark as invalid
+				if !exists || foundNode.UID != nodeRef.UID {
+					validNodeRefs = false
+					break
+				}
+			}
+
+			if validNodeRefs {
+				v1beta1conditions.MarkTrue(mp, clusterv1.ReplicasReadyV1Beta1Condition)
+				return ctrl.Result{}, nil
+			}
+		} else {
+			// If nodeRefMap is nil, we can't validate UIDs, so proceed with reconciliation
+			log.V(2).Info("NodeRefMap is nil, proceeding with reconciliation to validate NodeRefs")
+		}
 	}
 
 	// Check that the MachinePool has valid ProviderIDList.