Add volumeattach/volumedetach API

Longhorn volumes are attached to a node where the app is running.
Since the volumes we create in eve are RWO, ie only one node can attach at a time,
during failover we need to make sure the node that failed is detached from the volume.

The node that is taking over will automatically attach to the volume if no other node is
attached. Also, generally its very safe to detach and then attach to avoid any potential corruption.

Signed-off-by: Pramodh Pallapothu <pramodh@zededa.com>

pkg/pillar/kubeapi/vitoapiserver.go

@@ -313,6 +313,92 @@ func RolloutDiskToPVC(ctx context.Context, log *base.LogObject, exists bool,
 	return nil
 }
 
+// GetPVFromPVC : Returns volume name (PV) from the PVC name
+func GetPVFromPVC(pvcName string, log *base.LogObject) (string, error) {
+	// Get the Kubernetes clientset
+	clientset, err := GetClientSet()
+	if err != nil {
+		err = fmt.Errorf("failed to get clientset: %v", err)
+		log.Error(err)
+		return "", err
+	}
+	// Get the PersistentVolumeClaim (PVC)
+	pvc, err := clientset.CoreV1().PersistentVolumeClaims(EVEKubeNameSpace).Get(context.TODO(), pvcName, metav1.GetOptions{})
+	if err != nil {
+		err = fmt.Errorf("Error fetching PersistentVolumeClaim %s: %v", pvcName, err)
+		log.Error(err)
+		return "", err
+	}
+
+	// Get the associated PersistentVolume (PV) name
+	volumeName := pvc.Spec.VolumeName
+
+	log.Noticef("PersistentVolume %s is associated with PVC %s", volumeName, pvcName)
+
+	return volumeName, nil
+}
+
+// GetVolumeAttachmentFromPV : Return volume attachment if any for that PV along with nodename.
+// longhorn attaches to the PV to serve to the apps. This API returns the attachment name and nodename.
+// We use that attachment name to delete the attachment during failover.
+// Basically the attachment of previous node needs to be deleted to attach to current node.
+func GetVolumeAttachmentFromPV(volName string, log *base.LogObject) (string, string, error) {
+	// Get the Kubernetes clientset
+	clientset, err := GetClientSet()
+	if err != nil {
+		err = fmt.Errorf("failed to get clientset: %v", err)
+		log.Error(err)
+		return "", "", err
+	}
+	// List all VolumeAttachments and find the one corresponding to the PV
+	volumeAttachments, err := clientset.StorageV1().VolumeAttachments().List(context.TODO(), metav1.ListOptions{})
+	if err != nil {
+		err = fmt.Errorf("Error listing VolumeAttachments: %v", err)
+		log.Error(err)
+		return "", "", err
+	}
+
+	// Iterate through VolumeAttachments to find one that references the PV's CSI volume handle
+	for _, va := range volumeAttachments.Items {
+		if va.Spec.Source.PersistentVolumeName != nil && *va.Spec.Source.PersistentVolumeName == volName {
+			log.Noticef("VolumeAttachment for vol %s found: %s (attached to node: %s)\n", volName, va.Name, va.Spec.NodeName)
+			return va.Name, va.Spec.NodeName, nil
+		}
+	}
+
+	return "", "", nil
+}
+
+// DeleteVolumeAttachment : Delete the volumeattachment of given name
+func DeleteVolumeAttachment(vaName string, log *base.LogObject) error {
+	// Get the Kubernetes clientset
+	clientset, err := GetClientSet()
+	if err != nil {
+		err = fmt.Errorf("failed to get clientset: %v", err)
+		log.Error(err)
+		return err
+	}
+
+	// Force delete the VolumeAttachment with grace period set to 0
+	// This will ensure attachment is really deleted before its assigned to some other node.
+	deletePolicy := metav1.DeletePropagationForeground
+	deleteOptions := metav1.DeleteOptions{
+		GracePeriodSeconds: new(int64), // Set grace period to 0 for force deletion
+		PropagationPolicy:  &deletePolicy,
+	}
+
+	// Delete the VolumeAttachment
+	err = clientset.StorageV1().VolumeAttachments().Delete(context.TODO(), vaName, deleteOptions)
+	if err != nil {
+		err = fmt.Errorf("Error deleting VolumeAttachment %s: %v", vaName, err)
+		log.Error(err)
+		return err
+	}
+
+	log.Noticef("Deleted volumeattachment %s", vaName)
+	return nil
+}
+
 func stringPtr(str string) *string {
 	return &str
 }