feat: Add per-plugin nodeSelector support

Adds nodeSelector field to HighNodeUtilizationArgs and
LowNodeUtilizationArgs to allow filtering nodes per plugin.

This enables different plugins in the same profile to target
different sets of nodes based on labels, solving the limitation
where only global nodeSelector was available.

Use case: Run HighNodeUtilization only on nodes blocked by
cluster-autoscaler while other plugins run on all nodes.

Changes:
- Add NodeSelector field to both plugin Args structs
- Implement node filtering logic in Balance() methods
- Add nodeMatchesSelector helper function
- Generate deepcopy code for new fields
- Add comprehensive tests for nodeSelector logic

Addresses: #1486

Author: sarthaga

pkg/framework/plugins/nodeutilization/highnodeutilization.go

@@ -52,6 +52,7 @@ type HighNodeUtilization struct {
 	resourceNames  []v1.ResourceName
 	highThresholds api.ResourceThresholds
 	usageClient    usageClient
+	nodeSelector   map[string]string
 }
 
 // NewHighNodeUtilization builds plugin from its arguments while passing a handle.
@@ -126,6 +127,7 @@ func NewHighNodeUtilization(
 			resourceNames,
 			handle.GetPodsAssignedToNodeFunc(),
 		),
+		nodeSelector: args.NodeSelector,
 	}, nil
 }
 
@@ -140,6 +142,28 @@ func (h *HighNodeUtilization) Name() string {
 func (h *HighNodeUtilization) Balance(ctx context.Context, nodes []*v1.Node) *frameworktypes.Status {
 	logger := klog.FromContext(klog.NewContext(ctx, h.logger)).WithValues("ExtensionPoint", frameworktypes.BalanceExtensionPoint)
 
+	// Filter nodes by nodeSelector if specified
+	if len(h.nodeSelector) > 0 {
+		filteredNodes := []*v1.Node{}
+		for _, node := range nodes {
+			if nodeMatchesSelector(node, h.nodeSelector) {
+				filteredNodes = append(filteredNodes, node)
+			}
+		}
+
+		if len(filteredNodes) == 0 {
+			logger.V(1).Info("No nodes match the nodeSelector, skipping")
+			return nil
+		}
+
+		logger.V(1).Info(
+			"Filtered nodes by nodeSelector",
+			"totalNodes", len(nodes),
+			"matchedNodes", len(filteredNodes),
+		)
+		nodes = filteredNodes
+	}
+
 	if err := h.usageClient.sync(ctx, nodes); err != nil {
 		return &frameworktypes.Status{
 			Err: fmt.Errorf("error getting node usage: %v", err),
@@ -273,3 +297,13 @@ func (h *HighNodeUtilization) Balance(ctx context.Context, nodes []*v1.Node) *fr
 
 	return nil
 }
+
+// nodeMatchesSelector checks if a node matches all labels in the selector
+func nodeMatchesSelector(node *v1.Node, selector map[string]string) bool {
+	for key, value := range selector {
+		if nodeValue, exists := node.Labels[key]; !exists || nodeValue != value {
+			return false
+		}
+	}
+	return true
+}

pkg/framework/plugins/nodeutilization/lownodeutilization.go

@@ -52,6 +52,7 @@ type LowNodeUtilization struct {
 	resourceNames         []v1.ResourceName
 	extendedResourceNames []v1.ResourceName
 	usageClient           usageClient
+	nodeSelector          map[string]string
 }
 
 // NewLowNodeUtilization builds plugin from its arguments while passing a
@@ -126,6 +127,7 @@ func NewLowNodeUtilization(
 		extendedResourceNames: extendedResourceNames,
 		podFilter:             podFilter,
 		usageClient:           usageClient,
+		nodeSelector:          args.NodeSelector,
 	}, nil
 }
 
@@ -140,6 +142,28 @@ func (l *LowNodeUtilization) Name() string {
 func (l *LowNodeUtilization) Balance(ctx context.Context, nodes []*v1.Node) *frameworktypes.Status {
 	logger := klog.FromContext(klog.NewContext(ctx, l.logger)).WithValues("ExtensionPoint", frameworktypes.BalanceExtensionPoint)
 
+	// Filter nodes by nodeSelector if specified
+	if len(l.nodeSelector) > 0 {
+		filteredNodes := []*v1.Node{}
+		for _, node := range nodes {
+			if nodeMatchesSelector(node, l.nodeSelector) {
+				filteredNodes = append(filteredNodes, node)
+			}
+		}
+
+		if len(filteredNodes) == 0 {
+			logger.V(1).Info("No nodes match the nodeSelector, skipping")
+			return nil
+		}
+
+		logger.V(1).Info(
+			"Filtered nodes by nodeSelector",
+			"totalNodes", len(nodes),
+			"matchedNodes", len(filteredNodes),
+		)
+		nodes = filteredNodes
+	}
+
 	if err := l.usageClient.sync(ctx, nodes); err != nil {
 		return &frameworktypes.Status{
 			Err: fmt.Errorf("error getting node usage: %v", err),

pkg/framework/plugins/nodeutilization/nodeselector_test.go

@@ -0,0 +1,132 @@
+package nodeutilization
+
+import (
+	"testing"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestNodeMatchesSelector(t *testing.T) {
+	tests := []struct {
+		name     string
+		node     *v1.Node
+		selector map[string]string
+		expected bool
+	}{
+		{
+			name: "node matches single label",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "test-node",
+					Labels: map[string]string{
+						"env": "prod",
+					},
+				},
+			},
+			selector: map[string]string{
+				"env": "prod",
+			},
+			expected: true,
+		},
+		{
+			name: "node matches multiple labels",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "test-node",
+					Labels: map[string]string{
+						"env":  "prod",
+						"zone": "us-west",
+						"type": "worker",
+					},
+				},
+			},
+			selector: map[string]string{
+				"env":  "prod",
+				"zone": "us-west",
+			},
+			expected: true,
+		},
+		{
+			name: "node does not match label value",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "test-node",
+					Labels: map[string]string{
+						"env": "dev",
+					},
+				},
+			},
+			selector: map[string]string{
+				"env": "prod",
+			},
+			expected: false,
+		},
+		{
+			name: "node missing required label",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "test-node",
+					Labels: map[string]string{
+						"zone": "us-west",
+					},
+				},
+			},
+			selector: map[string]string{
+				"env": "prod",
+			},
+			expected: false,
+		},
+		{
+			name: "empty selector matches all nodes",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "test-node",
+					Labels: map[string]string{
+						"env": "prod",
+					},
+				},
+			},
+			selector: map[string]string{},
+			expected: true,
+		},
+		{
+			name: "node with no labels and non-empty selector",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:   "test-node",
+					Labels: map[string]string{},
+				},
+			},
+			selector: map[string]string{
+				"env": "prod",
+			},
+			expected: false,
+		},
+		{
+			name: "cluster-autoscaler scale-down disabled label",
+			node: &v1.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name: "test-node",
+					Labels: map[string]string{
+						"cluster-autoscaler.kubernetes.io/scale-down-disabled": "true",
+						"node.kubernetes.io/instance-type":                    "m5.large",
+					},
+				},
+			},
+			selector: map[string]string{
+				"cluster-autoscaler.kubernetes.io/scale-down-disabled": "true",
+			},
+			expected: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := nodeMatchesSelector(tt.node, tt.selector)
+			if result != tt.expected {
+				t.Errorf("nodeMatchesSelector() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}

pkg/framework/plugins/nodeutilization/types.go

@@ -49,6 +49,11 @@ type LowNodeUtilizationArgs struct {
 
 	// evictionLimits limits the number of evictions per domain. E.g. node, namespace, total.
 	EvictionLimits *api.EvictionLimits `json:"evictionLimits,omitempty"`
+
+	// NodeSelector filters which nodes are considered for eviction.
+	// Only nodes matching all specified labels will be processed by this plugin.
+	// If not set, all nodes are considered.
+	NodeSelector map[string]string `json:"nodeSelector,omitempty"`
 }
 
 // +k8s:deepcopy-gen=true
@@ -71,6 +76,11 @@ type HighNodeUtilizationArgs struct {
 	// considered while considering resources used by pods
 	// but then filtered out before eviction
 	EvictableNamespaces *api.Namespaces `json:"evictableNamespaces,omitempty"`
+
+	// NodeSelector filters which nodes are considered for eviction.
+	// Only nodes matching all specified labels will be processed by this plugin.
+	// If not set, all nodes are considered.
+	NodeSelector map[string]string `json:"nodeSelector,omitempty"`
 }
 
 // MetricsUtilization allow to consume actual resource utilization from metrics