test/integration: create nodes directly with kubernetes.io/hostname label

By generating the unique name in advance, the label also can be set to a
matching value directly in the Create request. This makes test startup in
test/integration/scheduler_perf a bit faster because the extra patching can be
avoided.

It also leads to a better label because previously, the unique label value
didn't match the node name. This is required for simulating dynamic resource
allocation, which relies on the label to track where an allocated claim is
available.

test/integration/framework/perf_utils.go

@@ -22,6 +22,7 @@ import (
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/rand"
 	clientset "k8s.io/client-go/kubernetes"
 	"k8s.io/klog/v2"
 	testutils "k8s.io/kubernetes/test/utils"
@@ -89,7 +90,20 @@ func (p *IntegrationTestNodePreparer) PrepareNodes(ctx context.Context, nextNode
 	for i := 0; i < numNodes; i++ {
 		var err error
 		for retry := 0; retry < retries; retry++ {
-			_, err = p.client.CoreV1().Nodes().Create(ctx, baseNode, metav1.CreateOptions{})
+			// Create nodes with the usual kubernetes.io/hostname label.
+			// For that we need to know the name in advance, if we want to
+			// do it in one request.
+			node := baseNode.DeepCopy()
+			name := node.Name
+			if name == "" {
+				name = node.GenerateName + rand.String(5)
+				node.Name = name
+			}
+			if node.Labels == nil {
+				node.Labels = make(map[string]string)
+			}
+			node.Labels["kubernetes.io/hostname"] = name
+			_, err = p.client.CoreV1().Nodes().Create(ctx, node, metav1.CreateOptions{})
 			if err == nil {
 				break
 			}