Allow 1.5% tolerance in memory capacity when comparing nodegroups

cluster-autoscaler/processors/nodegroupset/compare_nodegroups.go

@@ -31,11 +31,9 @@ const (
 	// MaxFreeDifferenceRatio describes how free resources (allocatable - daemon and system pods)
 	// can differ between groups in the same NodeGroupSet
 	MaxFreeDifferenceRatio = 0.05
-)
-
-var (
-	// MaxMemoryDifference describes how much memory capacity can differ but still be considered equal.
-	MaxMemoryDifference = resource.MustParse("256Mi")
+	// MaxCapacityMemoryDifferenceRatio describes how Node.Status.Capacity.Memory can differ between
+	// groups in the same NodeGroupSet
+	MaxCapacityMemoryDifferenceRatio = 0.015
 )
 
 // BasicIgnoredLabels define a set of basic labels that should be ignored when comparing the similarity
@@ -58,18 +56,25 @@ type NodeInfoComparator func(n1, n2 *schedulerframework.NodeInfo) bool
 func compareResourceMapsWithTolerance(resources map[apiv1.ResourceName][]resource.Quantity,
 	maxDifferenceRatio float64) bool {
 	for _, qtyList := range resources {
-		if len(qtyList) != 2 {
-			return false
-		}
-		larger := math.Max(float64(qtyList[0].MilliValue()), float64(qtyList[1].MilliValue()))
-		smaller := math.Min(float64(qtyList[0].MilliValue()), float64(qtyList[1].MilliValue()))
-		if larger-smaller > larger*maxDifferenceRatio {
+		if !compareResourceListWithTolerance(qtyList, maxDifferenceRatio) {
 			return false
 		}
 	}
 	return true
 }
 
+func compareResourceListWithTolerance(qtyList []resource.Quantity, maxDifferenceRatio float64) bool {
+	if len(qtyList) != 2 {
+		return false
+	}
+	larger := math.Max(float64(qtyList[0].MilliValue()), float64(qtyList[1].MilliValue()))
+	smaller := math.Min(float64(qtyList[0].MilliValue()), float64(qtyList[1].MilliValue()))
+	if larger-smaller > larger*maxDifferenceRatio {
+		return false
+	}
+	return true
+}
+
 func compareLabels(nodes []*schedulerframework.NodeInfo, ignoredLabels map[string]bool) bool {
 	labels := make(map[string][]string)
 	for _, node := range nodes {
@@ -133,11 +138,7 @@ func IsCloudProviderNodeInfoSimilar(n1, n2 *schedulerframework.NodeInfo, ignored
 		}
 		switch kind {
 		case apiv1.ResourceMemory:
-			// For memory capacity we allow a small tolerance
-			difference := absSub(qtyList[0], qtyList[1])
-
-			// Cmp compares two quantities and returns -1 for less than, 0 for equal, 1 for greater than
-			if difference.Cmp(MaxMemoryDifference) > 0 {
+			if !compareResourceListWithTolerance(qtyList, MaxCapacityMemoryDifferenceRatio) {
 				return false
 			}
 		default:
@@ -164,16 +165,3 @@ func IsCloudProviderNodeInfoSimilar(n1, n2 *schedulerframework.NodeInfo, ignored
 
 	return true
 }
-
-// absSub returns the absolute value of a - b
-func absSub(a, b resource.Quantity) *resource.Quantity {
-	q := &resource.Quantity{}
-	a.DeepCopyInto(q)
-	q.Sub(b)
-
-	if q.Sign() == -1 {
-		q.Neg()
-	}
-
-	return q
-}

cluster-autoscaler/processors/nodegroupset/compare_nodegroups_test.go

@@ -101,20 +101,20 @@ func TestNodesSimilarVariousRequirementsAndPods(t *testing.T) {
 
 func TestNodesSimilarVariousMemoryRequirements(t *testing.T) {
 	comparator := CreateGenericNodeInfoComparator([]string{})
-	n1 := BuildTestNode("node1", 1000, MaxMemoryDifference.Value())
+	n1 := BuildTestNode("node1", 1000, 1000)
 
 	// Different memory capacity within tolerance
-	n2 := BuildTestNode("node2", 1000, MaxMemoryDifference.Value())
-	n2.Status.Capacity[apiv1.ResourceMemory] = *resource.NewQuantity(2*MaxMemoryDifference.Value(), resource.DecimalSI)
+	n2 := BuildTestNode("node2", 1000, 1000)
+	n2.Status.Capacity[apiv1.ResourceMemory] = *resource.NewQuantity(1000-(1000*MaxCapacityMemoryDifferenceRatio)+1, resource.DecimalSI)
 	checkNodesSimilar(t, n1, n2, comparator, true)
 
 	// Different memory capacity exceeds tolerance
-	n3 := BuildTestNode("node3", 1000, MaxMemoryDifference.Value())
-	n3.Status.Capacity[apiv1.ResourceMemory] = *resource.NewQuantity(2*MaxMemoryDifference.Value()+1, resource.DecimalSI)
+	n3 := BuildTestNode("node3", 1000, 1000)
+	n3.Status.Capacity[apiv1.ResourceMemory] = *resource.NewQuantity(1000-(1000*MaxCapacityMemoryDifferenceRatio)+1, resource.DecimalSI)
 	checkNodesSimilar(t, n1, n3, comparator, false)
 }
 
-func TestNodesSimilarVariousLargeMemoryRequirements(t *testing.T) {
+func TestNodesSimilarVariousLargeMemoryRequirementsM5XLarge(t *testing.T) {
 	comparator := CreateGenericNodeInfoComparator([]string{})
 
 	// Use realistic memory capacity (taken from real nodes)
@@ -130,10 +130,30 @@ func TestNodesSimilarVariousLargeMemoryRequirements(t *testing.T) {
 	checkNodesSimilar(t, n1, n2, comparator, true)
 
 	// Different memory capacity exceeds tolerance
-	// Same value as q1 but with MaxMemoryDifference added twice
-	q3 := resource.MustParse("16116152Ki")
-	q3.Add(MaxMemoryDifference)
-	q3.Add(MaxMemoryDifference)
+	// Value of q1 * 1.02
+	q3 := resource.MustParse("16438475Ki")
+	n3 := BuildTestNode("node3", 1000, q3.Value())
+	checkNodesSimilar(t, n1, n3, comparator, false)
+}
+
+func TestNodesSimilarVariousLargeMemoryRequirementsM516XLarge(t *testing.T) {
+	comparator := CreateGenericNodeInfoComparator([]string{})
+
+	// Use realistic memory capacity (taken from real nodes)
+	// 257217528 KB ~= 256GiB (m5.16xLarge)
+	q1 := resource.MustParse("259970052Ki")
+	q2 := resource.MustParse("257217528Ki")
+
+	n1 := BuildTestNode("node1", 1000, q1.Value())
+
+	// Different memory capacity within tolerance
+	// Value taken from another m5.xLarge in a different zone
+	n2 := BuildTestNode("node2", 1000, q2.Value())
+	checkNodesSimilar(t, n1, n2, comparator, true)
+
+	// Different memory capacity exceeds tolerance
+	// Value of q1 * 1.02
+	q3 := resource.MustParse("265169453Ki")
 	n3 := BuildTestNode("node3", 1000, q3.Value())
 	checkNodesSimilar(t, n1, n3, comparator, false)
 }