spec: Preliminary volume expansion API.

csi.proto

@@ -57,6 +57,9 @@ service Controller {
 
   rpc ListSnapshots (ListSnapshotsRequest)
     returns (ListSnapshotsResponse) {}
+
+  rpc ControllerExpandVolume (ControllerExpandVolumeRequest)
+    returns (ControllerExpandVolumeResponse) {}
 }
 
 service Node {
@@ -75,6 +78,11 @@ service Node {
   rpc NodeGetVolumeStats (NodeGetVolumeStatsRequest)
     returns (NodeGetVolumeStatsResponse) {}
 
+
+  rpc NodeExpandVolume(NodeExpandVolumeRequest)
+    returns (NodeExpandVolumeResponse) {}
+
+
   rpc NodeGetCapabilities (NodeGetCapabilitiesRequest)
     returns (NodeGetCapabilitiesResponse) {}
 
@@ -116,7 +124,6 @@ message PluginCapability {
   message Service {
     enum Type {
       UNKNOWN = 0;
-
       // CONTROLLER_SERVICE indicates that the Plugin provides RPCs for
       // the ControllerService. Plugins SHOULD provide this capability.
       // In rare cases certain plugins MAY wish to omit the
@@ -138,9 +145,55 @@ message PluginCapability {
     Type type = 1;
   }
 
+  message VolumeExpansion {
+    enum Type {
+      UNKNOWN = 0;
+
+      // ONLINE indicates that volumes may be expanded when published to
+      // a node. When a Plugin implements this capability it MUST
+      // implement either the EXPAND_VOLUME controller capability or the
+      // EXPAND_VOLUME node capability or both. When a plugin supports
+      // ONLINE volume expansion and also has the EXPAND_VOLUME
+      // controller capability then the plugin MUST support expansion of
+      // volumes currently published and available on a node. When a
+      // plugin supports ONLINE volume expansion and also has the
+      // EXPAND_VOLUME node capability then the plugin MAY support
+      // expansion of node-published volume via NodeExpandVolume.
+      //
+      // Example 1: Given a shared filesystem volume (e.g. GlusterFs),
+      //   the Plugin may set the ONLINE volume expansion capability and
+      //   implement ControllerExpandVolume but not NodeExpandVolume.
+      //
+      // Example 2: Given a block storage volume type (e.g. EBS), the
+      //   Plugin may set the ONLINE volume expansion capability and
+      //   implement both ControllerExpandVolume and NodeExpandVolume.
+      //
+      // Example 3: Given a Plugin that supports volume expansion only
+      //   on upon a node, the Plugin may set the ONLINE volume
+      //   expansion capability and implement NodeExpandVolume but not
+      //   ControllerExpandVolume.
+      ONLINE = 1;
+
+      // OFFLINE indicates that volumes currently published and
+      // available on a node SHALL NOT be expanded via
+      // ControllerExpandVolume. When a plugin supports OFFLINE volume
+      // expansion it MUST implement either the EXPAND_VOLUME controller
+      // capability or both the EXPAND_VOLUME controller capability and
+      // the EXPAND_VOLUME node capability.
+      //
+      // Example 1: Given a block storage volume type (e.g. Azure Disk)
+      //   that does not support expansion of "node-attached" (i.e.
+      //   controller-published) volumes, the Plugin may indicate
+      //   OFFLINE volume expansion support and implement both
+      //   ControllerExpandVolume and NodeExpandVolume.
+      OFFLINE = 2;
+    }
+  }
+
   oneof type {
     // Service that the plugin supports.
     Service service = 1;
+    VolumeExpansion volume_expansion = 2;
   }
 }
 message ProbeRequest {
@@ -817,14 +870,19 @@ message ControllerServiceCapability {
       // snapshot.
       CREATE_DELETE_SNAPSHOT = 5;
       LIST_SNAPSHOTS = 6;
+
       // Plugins supporting volume cloning at the storage level MAY
       // report this capability. The source volume MUST be managed by
       // the same plugin. Not all volume sources and parameters
       // combinations MAY work.
       CLONE_VOLUME = 7;
+
       // Indicates the SP supports ControllerPublishVolume.readonly
       // field.
       PUBLISH_READONLY = 8;
+
+      // See VolumeExpansion for details.
+      EXPAND_VOLUME = 9;
     }
 
     Type type = 1;
@@ -967,6 +1025,28 @@ message ListSnapshotsResponse {
   // An empty string is equal to an unspecified field value.
   string next_token = 2;
 }
+message ControllerExpandVolumeRequest {
+  // The ID of the volume to expand. This field is REQUIRED.
+  string volume_id = 1;
+
+  // This allows CO to specify the capacity requirements of the volume
+  // after expansion. This field is REQUIRED.
+  CapacityRange capacity_range = 2;
+
+  // Secrets required by the plugin for expanding the volume.
+  // This field is OPTIONAL.
+  map<string, string> secrets = 3 [(csi_secret) = true];
+}
+
+message ControllerExpandVolumeResponse {
+  // Capacity of volume after expansion. This field is REQUIRED.
+  int64 capacity_bytes = 1;
+
+  // Whether node expansion is required for the volume. When true
+  // the CO MUST make NodeExpandVolume RPC call on the node. This field
+  // is REQUIRED.
+  bool node_expansion_required = 2;
+}
 message NodeStageVolumeRequest {
   // The ID of the volume to publish. This field is REQUIRED.
   string volume_id = 1;
@@ -1144,6 +1224,8 @@ message NodeServiceCapability {
       // then it MUST implement NodeGetVolumeStats RPC
       // call for fetching volume statistics.
       GET_VOLUME_STATS = 2;
+      // See VolumeExpansion for details.
+      EXPAND_VOLUME = 3;
     }
 
     Type type = 1;
@@ -1194,3 +1276,23 @@ message NodeGetInfoResponse {
   // "Z2".
   Topology accessible_topology = 3;
 }
+message NodeExpandVolumeRequest {
+  // The ID of the volume. This field is REQUIRED.
+  string volume_id = 1;
+
+  // The path on which volume is available. This field is REQUIRED.
+  string volume_path = 2;
+
+  // This allows CO to specify the capacity requirements of the volume
+  // after expansion. If capacity_range is omitted then a plugin MAY
+  // inspect the file system of the volume to determine the maximum
+  // capacity to which the volume can be expanded. In such cases a
+  // plugin MAY expand the volume to its maximum capacity.
+  // This field is OPTIONAL.
+  CapacityRange capacity_range = 3;
+}
+
+message NodeExpandVolumeResponse {
+  // The capacity of the volume in bytes. This field is OPTIONAL.
+  int64 capacity_bytes = 1;
+}