Preserve old observedGen if incoming attempts to clear it

pkg/registry/core/pod/strategy.go

@@ -227,9 +227,38 @@ func (podStatusStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.
 		newPod.Status.QOSClass = oldPod.Status.QOSClass
 	}
 
+	preserveOldObservedGeneration(newPod, oldPod)
 	podutil.DropDisabledPodFields(newPod, oldPod)
 }
 
+// If a client request tries to clear `observedGeneration`, in the pod status or
+// conditions, we preserve the original value.
+func preserveOldObservedGeneration(newPod, oldPod *api.Pod) {
+	if newPod.Status.ObservedGeneration == 0 {
+		newPod.Status.ObservedGeneration = oldPod.Status.ObservedGeneration
+	}
+
+	// Remember observedGeneration values from old status conditions.
+	// This is a list per type because validation permits multiple conditions with the same type.
+	oldConditionGenerations := map[api.PodConditionType][]int64{}
+	for _, oldCondition := range oldPod.Status.Conditions {
+		oldConditionGenerations[oldCondition.Type] = append(oldConditionGenerations[oldCondition.Type], oldCondition.ObservedGeneration)
+	}
+
+	// For any conditions in the new status without observedGeneration set, preserve the old value.
+	for i, newCondition := range newPod.Status.Conditions {
+		oldGeneration := int64(0)
+		if oldGenerations, ok := oldConditionGenerations[newCondition.Type]; ok && len(oldGenerations) > 0 {
+			oldGeneration = oldGenerations[0]
+			oldConditionGenerations[newCondition.Type] = oldGenerations[1:]
+		}
+
+		if newCondition.ObservedGeneration == 0 {
+			newPod.Status.Conditions[i].ObservedGeneration = oldGeneration
+		}
+	}
+}
+
 func (podStatusStrategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList {
 	pod := obj.(*api.Pod)
 	oldPod := old.(*api.Pod)

pkg/registry/core/pod/strategy_test.go

@@ -3396,6 +3396,161 @@ func TestStatusPrepareForUpdate(t *testing.T) {
 				},
 			},
 		},
+		{
+			description: "preserve old status.observedGeneration if empty",
+			oldPod: &api.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Status: api.PodStatus{
+					ObservedGeneration: 20,
+				},
+			},
+			newPod: &api.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+			},
+			expected: &api.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Status: api.PodStatus{
+					ObservedGeneration: 20,
+				},
+			},
+		},
+		{
+			description: "preserve old conditions.observedGeneration if empty",
+			oldPod: &api.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Status: api.PodStatus{
+					Conditions: []api.PodCondition{
+						{
+							Type:   "old=without,new=without",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:               "old=with,new=without",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:   "old=without,new=with",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:               "old=with,new=with",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:               "removed-condition",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:   "duplicate type",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 2,
+						},
+					},
+				},
+			},
+			newPod: &api.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Status: api.PodStatus{
+					Conditions: []api.PodCondition{
+						{
+							Type:   "old=without,new=without",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:   "old=with,new=without",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:               "old=without,new=with",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:               "old=with,new=with",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:               "new-condition",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:   "duplicate type",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 2,
+						},
+					},
+				},
+			},
+			expected: &api.Pod{
+				ObjectMeta: metav1.ObjectMeta{Name: "pod"},
+				Status: api.PodStatus{
+					Conditions: []api.PodCondition{
+						{
+							Type:   "old=without,new=without",
+							Status: api.ConditionTrue,
+						},
+						{
+							Type:               "old=with,new=without",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:               "old=without,new=with",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:               "old=with,new=with",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 20,
+						},
+						{
+							Type:               "new-condition",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 1,
+						},
+						{
+							Type:               "duplicate type",
+							Status:             api.ConditionTrue,
+							ObservedGeneration: 2,
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for _, tc := range testCases {