Add "auto" provisioning type.

Automatically use hostpath if pod is on same host as zfs pool.

This addresses #85. When storage class type is set to auto,
automatically create a hostpath volume when the scheduler selects the
specified node to run the pod, otherwise fallback to using NFS.

Note this only works when volumeBindingMode is set to
WaitForFirstConsumer in the storage class. Otherwise, when set to
Immediate, volumes will be pre-provisioned before the scheduler selects a
node for the pod consuming the volume, and options.SelectedNode will be
unset.

Note that there could be unintended side-effects if multiple pods using
the volume claim are scheduled on different nodes, depending on which
pods gets scheduled first. If the first pod gets scheduled on the ZFS
host, it will automatically use a hostpath volume and node affinity will
be set so that other pods will be prevented from running on other nodes.
On the other hand, if the second pod gets scheduled on a node which is
not the ZFS host, it will use a NFS volume, and subsequent pods will
also use NFS, even if scheduled to run on the ZFS host.

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

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

charts/kubernetes-zfs-provisioner/values.yaml

@@ -37,7 +37,7 @@ storageClass:
     #   policy: "Delete"
     #   # -- NFS export properties (see `exports(5)`)
     #   shareProperties: ""
-    #   # -- Provision type, one of [`nfs`, `hostpath`]
+    #   # -- Provision type, one of [`nfs`, `hostpath`, `auto`]
     #   type: "nfs"
     #   # -- Override `kubernetes.io/hostname` from `hostName` parameter for
     #   # `HostPath` node affinity

pkg/provisioner/parameters.go

@@ -19,12 +19,20 @@ const (
 parameters:
   parentDataset: tank/volumes
   hostname: my-zfs-host.localdomain
-  type: nfs|hostpath
+  type: nfs|hostPath|auto
   shareProperties: rw=10.0.0.0/8,no_root_squash
   node: my-zfs-host
   reserveSpace: true|false
 */
 
+type ProvisioningType string
+
+const (
+	Nfs ProvisioningType = "nfs"
+	HostPath ProvisioningType = "hostPath"
+	Auto ProvisioningType = "auto"
+)
+
 type (
 	// ZFSStorageClassParameters represents the parameters on the `StorageClass`
 	// object. It is used to ease access and validate those parameters at run time.
@@ -33,18 +41,13 @@ type (
 		ParentDataset string
 		// Hostname of the target ZFS host. Will be used to connect over SSH.
 		Hostname     string
-		NFS          *NFSParameters
-		HostPath     *HostPathParameters
+		Type         ProvisioningType
+		// NFSShareProperties specifies additional properties to pass to 'zfs create sharenfs=%s'.
+		NFSShareProperties string
+		// HostPathNodeName overrides the hostname if the Kubernetes node name is different than the ZFS target host. Used for Affinity
+		HostPathNodeName string
 		ReserveSpace bool
 	}
-	NFSParameters struct {
-		// ShareProperties specifies additional properties to pass to 'zfs create sharenfs=%s'.
-		ShareProperties string
-	}
-	HostPathParameters struct {
-		// NodeName overrides the hostname if the Kubernetes node name is different than the ZFS target host. Used for Affinity
-		NodeName string
-	}
 )
 
 // NewStorageClassParameters takes a storage class parameters, validates it for invalid configuration and returns a
@@ -79,16 +82,26 @@ func NewStorageClassParameters(parameters map[string]string) (*ZFSStorageClassPa
 	typeParam := parameters[TypeParameter]
 	switch typeParam {
 	case "hostpath", "hostPath", "HostPath", "Hostpath", "HOSTPATH":
-		p.HostPath = &HostPathParameters{NodeName: parameters[NodeNameParameter]}
-		return p, nil
+		p.Type = HostPath
 	case "nfs", "Nfs", "NFS":
+		p.Type = Nfs
+	case "auto", "Auto", "AUTO":
+		p.Type = Auto
+	default:
+		return nil, fmt.Errorf("invalid '%s' parameter value: %s", TypeParameter, typeParam)
+	}
+
+	if p.Type == HostPath || p.Type == Auto {
+		p.HostPathNodeName = parameters[NodeNameParameter]
+	}
+
+	if p.Type == Nfs || p.Type == Auto {
 		shareProps := parameters[SharePropertiesParameter]
 		if shareProps == "" {
 			shareProps = "on"
 		}
-		p.NFS = &NFSParameters{ShareProperties: shareProps}
-		return p, nil
-	default:
-		return nil, fmt.Errorf("invalid '%s' parameter value: %s", TypeParameter, typeParam)
+		p.NFSShareProperties = shareProps
 	}
+
+	return p, nil
 }

pkg/provisioner/parameters_test.go

@@ -77,7 +77,7 @@ func TestNewStorageClassParameters(t *testing.T) {
 					SharePropertiesParameter: "rw",
 				},
 			},
-			want: &ZFSStorageClassParameters{NFS: &NFSParameters{ShareProperties: "rw"}},
+			want: &ZFSStorageClassParameters{NFSShareProperties: "rw"},
 		},
 		{
 			name: "GivenCorrectSpec_WhenTypeNfsWithoutProperties_ThenReturnNfsParametersWithDefault",
@@ -88,7 +88,7 @@ func TestNewStorageClassParameters(t *testing.T) {
 					TypeParameter:          "nfs",
 				},
 			},
-			want: &ZFSStorageClassParameters{NFS: &NFSParameters{ShareProperties: "on"}},
+			want: &ZFSStorageClassParameters{NFSShareProperties: "on"},
 		},
 		{
 			name: "GivenCorrectSpec_WhenTypeHostPath_ThenReturnHostPathParameters",
@@ -100,7 +100,7 @@ func TestNewStorageClassParameters(t *testing.T) {
 					NodeNameParameter:      "my-node",
 				},
 			},
-			want: &ZFSStorageClassParameters{HostPath: &HostPathParameters{NodeName: "my-node"}},
+			want: &ZFSStorageClassParameters{HostPathNodeName: "my-node"},
 		},
 	}
 	for _, tt := range tests {
@@ -112,8 +112,8 @@ func TestNewStorageClassParameters(t *testing.T) {
 				return
 			}
 			assert.NoError(t, err)
-			assert.Equal(t, tt.want.NFS, result.NFS)
-			assert.Equal(t, tt.want.HostPath, result.HostPath)
+			assert.Equal(t, tt.want.NFSShareProperties, result.NFSShareProperties)
+			assert.Equal(t, tt.want.HostPathNodeName, result.HostPathNodeName)
 		})
 	}
 }

pkg/provisioner/provision.go

@@ -24,8 +24,10 @@ func (p *ZFSProvisioner) Provision(ctx context.Context, options controller.Provi
 	datasetPath := fmt.Sprintf("%s/%s", parameters.ParentDataset, options.PVName)
 	properties := make(map[string]string)
 
-	if parameters.NFS != nil {
-		properties["sharenfs"] = parameters.NFS.ShareProperties
+	useHostPath := true
+	if parameters.Type == "nfs" || parameters.Type == "auto" && (options.SelectedNode == nil || parameters.HostPathNodeName != options.SelectedNode.Name) {
+		useHostPath = false
+		properties[ShareNfsProperty] = parameters.NFSShareProperties
 	}
 
 	var reclaimPolicy v1.PersistentVolumeReclaimPolicy
@@ -77,24 +79,15 @@ func (p *ZFSProvisioner) Provision(ctx context.Context, options controller.Provi
 			Capacity: v1.ResourceList{
 				v1.ResourceStorage: options.PVC.Spec.Resources.Requests[v1.ResourceStorage],
 			},
-			PersistentVolumeSource: createVolumeSource(parameters, dataset),
-			NodeAffinity:           createNodeAffinity(parameters),
+			PersistentVolumeSource: createVolumeSource(parameters, dataset, useHostPath),
+			NodeAffinity:           createNodeAffinity(parameters, useHostPath),
 		},
 	}
 	return pv, controller.ProvisioningFinished, nil
 }
 
-func createVolumeSource(parameters *ZFSStorageClassParameters, dataset *zfs.Dataset) v1.PersistentVolumeSource {
-	if parameters.NFS != nil {
-		return v1.PersistentVolumeSource{
-			NFS: &v1.NFSVolumeSource{
-				Server:   parameters.Hostname,
-				Path:     dataset.Mountpoint,
-				ReadOnly: false,
-			},
-		}
-	}
-	if parameters.HostPath != nil {
+func createVolumeSource(parameters *ZFSStorageClassParameters, dataset *zfs.Dataset, useHostPath bool) v1.PersistentVolumeSource {
+	if useHostPath {
 		hostPathType := v1.HostPathDirectory
 		return v1.PersistentVolumeSource{
 			HostPath: &v1.HostPathVolumeSource{
@@ -103,27 +96,34 @@ func createVolumeSource(parameters *ZFSStorageClassParameters, dataset *zfs.Data
 			},
 		}
 	}
-	klog.Exitf("Programmer error: Missing implementation for volume source: %v", parameters)
-	return v1.PersistentVolumeSource{}
+
+	return v1.PersistentVolumeSource{
+		NFS: &v1.NFSVolumeSource{
+			Server:   parameters.Hostname,
+			Path:     dataset.Mountpoint,
+			ReadOnly: false,
+		},
+	}
 }
 
-func createNodeAffinity(parameters *ZFSStorageClassParameters) *v1.VolumeNodeAffinity {
-	if parameters.HostPath != nil {
-		node := parameters.HostPath.NodeName
-		if node == "" {
-			node = parameters.Hostname
-		}
-		return &v1.VolumeNodeAffinity{Required: &v1.NodeSelector{NodeSelectorTerms: []v1.NodeSelectorTerm{
-			{
-				MatchExpressions: []v1.NodeSelectorRequirement{
-					{
-						Values:   []string{node},
-						Operator: v1.NodeSelectorOpIn,
-						Key:      v1.LabelHostname,
-					},
+func createNodeAffinity(parameters *ZFSStorageClassParameters, useHostPath bool) *v1.VolumeNodeAffinity {
+	if !useHostPath {
+		return nil
+	}
+
+	node := parameters.HostPathNodeName
+	if node == "" {
+		node = parameters.Hostname
+	}
+	return &v1.VolumeNodeAffinity{Required: &v1.NodeSelector{NodeSelectorTerms: []v1.NodeSelectorTerm{
+		{
+			MatchExpressions: []v1.NodeSelectorRequirement{
+				{
+					Values:   []string{node},
+					Operator: v1.NodeSelectorOpIn,
+					Key:      v1.LabelHostname,
 				},
 			},
-		}}}
-	}
-	return nil
+		},
+	}}}
 }

pkg/provisioner/provisioner.go

@@ -11,6 +11,7 @@ const (
 
 	RefQuotaProperty       = "refquota"
 	RefReservationProperty = "refreservation"
+	ShareNfsProperty       = "sharenfs"
 	ManagedByProperty      = "io.kubernetes.pv.zfs:managed_by"
 	ReclaimPolicyProperty  = "io.kubernetes.pv.zfs:reclaim_policy"
 )