Added volume.Creater interface and simple HostPath implementation

pkg/volume/plugins.go

@@ -33,14 +33,13 @@ import (
 )
 
 // VolumeOptions contains option information about a volume.
-//
-// Currently, this struct containers only a single field for the
-// rootcontext of the volume.  This is a temporary measure in order
-// to set the rootContext of tmpfs mounts correctly; it will be replaced
-// and expanded on by future SecurityContext work.
 type VolumeOptions struct {
 	// The rootcontext to use when performing mounts for a volume.
+	// This is a temporary measure in order to set the rootContext of tmpfs mounts correctly.
+	// it will be replaced and expanded on by future SecurityContext work.
 	RootContext string
+	// CapacityMB is the size in MB of a volume.
+	CapacityMB int
 }
 
 // VolumePlugin is an interface to volume plugins that can be used on a
@@ -99,6 +98,14 @@ type DeletableVolumePlugin interface {
 	NewDeleter(spec *Spec) (Deleter, error)
 }
 
+// CreatableVolumePlugin is an extended interface of VolumePlugin and is used to create persistent volumes for the cluster.
+type CreatableVolumePlugin interface {
+	VolumePlugin
+	// NewCreater creates a new volume.Creater which knows how to create PersistentVolumes in accordance with
+	// the plugin's underlying storage provider
+	NewCreater(options VolumeOptions) (Creater, error)
+}
+
 // VolumeHost is an interface that plugins can use to access the kubelet.
 type VolumeHost interface {
 	// GetPluginDir returns the absolute path to a directory under which
@@ -345,6 +352,19 @@ func (pm *VolumePluginMgr) FindDeletablePluginBySpec(spec *Spec) (DeletableVolum
 	return nil, fmt.Errorf("no deletable volume plugin matched")
 }
 
+// FindCreatablePluginBySpec fetches a persistent volume plugin by name.  If no plugin
+// is found, returns error.
+func (pm *VolumePluginMgr) FindCreatablePluginBySpec(spec *Spec) (CreatableVolumePlugin, error) {
+	volumePlugin, err := pm.FindPluginBySpec(spec)
+	if err != nil {
+		return nil, err
+	}
+	if creatableVolumePlugin, ok := volumePlugin.(CreatableVolumePlugin); ok {
+		return creatableVolumePlugin, nil
+	}
+	return nil, fmt.Errorf("no creatable volume plugin matched")
+}
+
 // NewPersistentVolumeRecyclerPodTemplate creates a template for a recycler pod.  By default, a recycler pod simply runs
 // "rm -rf" on a volume and tests for emptiness.  Most attributes of the template will be correct for most
 // plugin implementations.  The following attributes can be overridden per plugin via configuration: