e2e: fetch volume metrics from Kubelet

Test if metrics are available at all. The actual values are a little
difficult to validate.

BlockMode volumes support metrics since Kubernetes 1.22.

See-also: kubernetes/kubernetes#97972
Signed-off-by: Niels de Vos <ndevos@redhat.com>

e2e/node.go

@@ -2,7 +2,9 @@ package e2e
 
 import (
 	"context"
+	"errors"
 
+	core "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/kubernetes/test/e2e/framework"
@@ -42,3 +44,20 @@ func checkNodeHasLabel(c kubernetes.Interface, labelKey, labelValue string) erro
 	}
 	return nil
 }
+
+// List all nodes in the cluster (we have one), and return the IP-address.
+// Possibly need to add a selector, pick the node where a Pod is running?
+func getKubeletIP(c kubernetes.Interface) (string, error) {
+	nodes, err := c.CoreV1().Nodes().List(context.TODO(), metav1.ListOptions{})
+	if err != nil {
+		return "", err
+	}
+
+	for _, address := range nodes.Items[0].Status.Addresses {
+		if address.Type == core.NodeInternalIP {
+			return address.Address, nil
+		}
+	}
+
+	return "", errors.New("could not find internal IP for node")
+}