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Specify InlineVolumeSpec field in VolumeAttachmentSource for in-line handling 

Signed-off-by: Deep Debroy <ddebroy@docker.com>
This commit is contained in:
Deep Debroy 2019-04-29 11:19:32 -07:00
parent befd4ea1e2
commit cf0b2483f9
1 changed files with 28 additions and 40 deletions
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68
contributors/design-proposals/storage/csi-migration.md
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@ -179,10 +179,9 @@ type CSITranslator interface {
// by the `Driver` field in the CSI Source. The input PV object will not be modified.
TranslateCSIPVToInTree(pv *v1.PersistentVolume) (*v1.PersistentVolume, error) {
// TranslateInTreeVolumeToCSI takes an inline intree volume and will translate
// the in-tree volume source to a CSIPersistentVolumeSource
// A PV object containing the CSIPersistentVolumeSource in it's spec is returned
TranslateInTreeInlineVolumeToCSI(volume *v1.Volume (*v1.PersistentVolume, error) {
// TranslateInTreeInlineVolumeToPVSpec takes an inline intree volume and will translate
// the in-tree volume source to a PersistentVolumeSpec containing a CSIPersistentVolumeSource
TranslateInTreeInlineVolumeToPVSpec(volume *v1.Volume) (*v1.PersistentVolumeSpec, error) {
// IsMigratableByName tests whether there is Migration logic for the in-tree plugin
// for the given `pluginName`
@ -191,12 +190,6 @@ type CSITranslator interface {
// GetCSINameFromIntreeName maps the name of a CSI driver to its in-tree version
GetCSINameFromIntreeName(pluginName string) (string, error) {
// GetAccessModes returns a default access mode based on the plugin and volume spec
GetAccessModes(pluginName string, vol *v1.Volume) (csi.VolumeCapability_AccessMode, error) {
// GetMountOptions returns a default mount option based on the plugin and volume spec
GetMountOptions(pluginName string, vol *v1.Volume) (string) {
// IsPVMigratable tests whether there is Migration logic for the given Persistent Volume
IsPVMigratable(pv *v1.PersistentVolume) bool {
@ -244,54 +237,49 @@ with the in-tree plugin, the VolumeAttachment object becomes orphaned.
### In-line Volumes
In-line controller calls are a special case because there is no PV. In this case
we will translate the in-line volume source into a CSIPersistentVolumeSource
and copy it to the field `VolumeAttachment.Spec.Source.VolumeAttachmentSource.InlineCSIVolumeSource`.
The VolumeAttachment name must be made with the CSI Translated version of the
In-line controller calls are a special case because there is no PV. In this case,
we will translate the in-line Volume into a PersistentVolumeSpec using
plugin-specific translation logic in the CSI translation library method,
`TranslateInTreeInlineVolumeToPVSpec`. The resulting PersistentVolumeSpec will
and be stored in a new field `VolumeAttachment.Spec.Source.VolumeAttachmentSource.InlineVolumeSpec`.
The plugin-specific CSI translation logic invoked by `TranslateInTreeInlineVolumeToPVSpec`
will need to populate the `CSIPersistentVolumeSource` field along with appropriate
values for `AccessModes` and `MountOptions` fields in
`VolumeAttachment.Spec.Source.VolumeAttachmentSource.InlineVolumeSpec`. Since
`AccessModes` and `MountOptions` are not specified for inline volumes, default values
for these fields suitable for the CSI plugin will need to be populated in addition
to translation logic to populate `CSIPersistentVolumeSource`.
The VolumeAttachment name must be made with the CSI translated version of the
VolumeSource in order for it to be discoverable by Detach and WaitForAttach
(described in more detail below).
The CSI Attacher will have to be modified to also check for `InlineCSIVolumeSource`
besides the `PersistentVolumeName`. Only one of the two may be specified. If `PersistentVolumeName`
is empty and `InlineCSIVolumeSource` is set, the CSI Attacher will not look for
an associated PV in it's PV informer cache as it implies the inline volume scenario
The CSI Attacher will have to be modified to also check for `InlineVolumeSpec`
besides the `PersistentVolumeName`. Only one of the two may be specified. If `PersistentVolumeName`
is empty and `InlineVolumeSpec` is set, the CSI Attacher will not look for
an associated PV in it's PV informer cache as it implies the inline volume scenario
(where no PVs are created).
The CSI Attacher will have access to most of the data it requires for handling in-line
volumes attachment (through the CSI plugins) from `InlineCSIVolumeSource`. However
a few fields require special handling due to the absence of a PV where such fields
are assigned desired values. Specifically, reasonable `MountOptions` and
`AccessModes` settings need to be determined by plugin-specific APIs:
`GetMountOptions` and `GetAccessModes` that sets the default values for
these parameters and satisfies the broadest of scenarios supported by the CSI
plugin. Some specific example:
1. If GCEPersistentDiskVolumeSource.ReadOnly is true, `GetAccessModes` for GCE PD
can return csi.VolumeCapability_AccessMode_MULTI_NODE_READER_ONLY. If
If GCEPersistentDiskVolumeSource.ReadOnly is false, `GetAccessModes` for GCE PD
can return csi.VolumeCapability_AccessMode_SINGLE_NODE_WRITER
2. The EBS CSI driver only supports csi.VolumeCapability_AccessMode_SINGLE_NODE_WRITER
today . So `GetAccessModes` for EBS can always return
csi.VolumeCapability_AccessMode_SINGLE_NODE_WRITER until further modes are supported.
3. For shared FS plugins like AzureFile or CephFS, `GetAccessModes` may return
csi.VolumeCapability_AccessMode_MULTI_NODE_MULTI_WRITER
The CSI Attacher will have access to all the data it requires for handling in-line
volumes attachment (through the CSI plugins) from fields in the `InlineVolumeSpec`.
The new VolumeAttachmentSource API will look as such:
```
// VolumeAttachmentSource represents a volume that should be attached.
// Right now only PersistenVolumes can be attached via external attacher,
// in future we may allow also inline volumes in pods.
// Inline volumes and Persistent volumes can be attached via external attacher.
// Exactly one member can be set.
type VolumeAttachmentSource struct {
// Name of the persistent volume to attach.
// +optional
PersistentVolumeName *string `json:"persistentVolumeName,omitempty" protobuf:"bytes,1,opt,name=persistentVolumeName"`
// Translated VolumeSource from a pod to a CSIPersistentVolumeSource
// to support shimming of in-tree inline volumes to a CSI backend.
// A PersistentVolumeSpec whose fields contain translated data from a pod's inline
// VolumeSource to support shimming of in-tree inline volumes to a CSI backend.
// This field is alpha-level and is only honored by servers that
// enable the CSIMigration feature.
// +optional
InlineCSIVolumeSource *v1.CSIPersistentVolumeSource `json:"inlineCSIVolumeSource,omitempty" protobuf:"bytes,2,opt,name=inlineCSIVolumeSource"`
InlineVolumeSpec *v1.PersistentVolumeSpec `json:"inlineVolumeSpec,omitempty" protobuf:"bytes,2,opt,name=inlineVolumeSpec"`
}
```