Auto: unconditionally set affinity when RWO or RWOP is requested.

Force HostPath to be used preemptively instead of letting the scheduler
choose where to place the first pod.

Also add support for ReadWriteOncePod.

README.md

@@ -16,10 +16,13 @@ but the `PersistentVolume` objects will have a [NodeAffinity][node affinity] con
 ![architecture with Hostpath](architecture.hostpath.drawio.svg "Architecture with Hostpath provisioning")
 
 As a third option, if the ZFS host is part of the cluster, you can let the provisioner choose
-whether [NFS][nfs] or [HostPath][hostpath] is used with the `Auto` mode. If the scheduler
-decides to place a Pod onto the ZFS host, *and* the requested access mode in the Persistent Volume
-Claim is `ReadWriteOnce` (the volume can only be accessed by pods running on the same node)
-[HostPath][hostpath] will automatically be used, otherwise [NFS][nfs] will be used.
+whether [NFS][nfs] or [HostPath][hostpath] is used with the `Auto` mode. If the requested
+[AccessModes][access modes] in the Persistent Volume Claim contains `ReadWriteOnce` (the volume
+can only be accessed by pods running on the same node), or `ReadWriteOncePod` (the volume can only
+be accessed by one single Pod at any time), then [HostPath][hostpath] will be used and
+the [NodeAffinity][node affinity] will be configured on the `PersistentVolume` objects so the
+scheduler will automatically place the corresponding Pods onto the ZFS host. Otherwise
+[NFS][nfs] will be used and [NodeAffinity][node affinity] will not be set.
 
 Currently all ZFS attributes are inherited from the parent dataset.
 
@@ -92,8 +95,8 @@ parameters:
 For NFS, you can also specify other options, as described in [exports(5)][man exports].
 
 The following example configures a storage class using the `Auto` type. The provisioner
-will decide whether [HostPath][hostpath] or [NFS][nfs] will be used based on where the
-pods are being scheduled.
+will decide whether [HostPath][hostpath] or [NFS][nfs] will be used based on the
+[AccessModess][access modes] requested by the persistent volume claim.
 
 ```yaml
 kind: StorageClass
@@ -215,3 +218,4 @@ I (@ccremer) have been allowed to take over maintenance for this repository.
 [helm chart]: https://github.com/ccremer/kubernetes-zfs-provisioner/blob/master/charts/kubernetes-zfs-provisioner/README.md
 [gentics]: https://www.gentics.com/genticscms/index.en.html
 [gentics repo]: https://github.com/gentics/kubernetes-zfs-provisioner
+[access modes]: https://kubernetes.io/docs/concepts/storage/persistent-volumes/#access-modes

charts/kubernetes-zfs-provisioner/templates/storageclass.yaml

@@ -12,9 +12,6 @@ metadata:
     {{ toYaml . | nindent 4 }}
 {{- end }}
 provisioner: {{ $.Values.provisioner.instance }}
-{{- if eq .type "auto" }}
-volumeBindingMode: WaitForFirstConsumer
-{{- end }}
 reclaimPolicy: {{ .policy | default "Delete" }}
 parameters:
   parentDataset: {{ .parentDataset }}

pkg/provisioner/provision.go

@@ -73,7 +73,7 @@ func (p *ZFSProvisioner) Provision(ctx context.Context, options controller.Provi
 		},
 		Spec: v1.PersistentVolumeSpec{
 			PersistentVolumeReclaimPolicy: reclaimPolicy,
-			AccessModes:                   createAccessModes(useHostPath),
+			AccessModes:                   createAccessModes(options, useHostPath),
 			Capacity: v1.ResourceList{
 				v1.ResourceStorage: options.PVC.Spec.Resources.Requests[v1.ResourceStorage],
 			},
@@ -91,17 +91,17 @@ func canUseHostPath(parameters *ZFSStorageClassParameters, options controller.Pr
 	case HostPath:
 		return true
 	case Auto:
-		if options.SelectedNode == nil || parameters.HostPathNodeName != options.SelectedNode.Name {
-			return false
-		}
 		if slices.Contains(options.PVC.Spec.AccessModes, v1.ReadOnlyMany) || slices.Contains(options.PVC.Spec.AccessModes, v1.ReadWriteMany) {
 			return false
 		}
 	}
 	return true
 }
 
-func createAccessModes(useHostPath bool) []v1.PersistentVolumeAccessMode {
+func createAccessModes(options controller.ProvisionOptions, useHostPath bool) []v1.PersistentVolumeAccessMode {
+	if slices.Contains(options.PVC.Spec.AccessModes, v1.ReadWriteOncePod) {
+		return []v1.PersistentVolumeAccessMode{v1.ReadWriteOncePod}
+	}
 	accessModes := []v1.PersistentVolumeAccessMode{v1.ReadWriteOnce}
 	if !useHostPath {
 		accessModes = append(accessModes, v1.ReadOnlyMany, v1.ReadWriteMany)