Renamed capability for ModifyVolumeGroupMembership

Addressed review comments

Author: xing-yang

Diff for: csi.proto

@@ -111,8 +111,8 @@ service Controller {
         option (alpha_method) = true;
     }
 
-  rpc ModifyVolumeGroup(ModifyVolumeGroupRequest)
-    returns (ModifyVolumeGroupResponse) {
+  rpc ModifyVolumeGroupMembership(ModifyVolumeGroupMembershipRequest)
+    returns (ModifyVolumeGroupMembershipResponse) {
         option (alpha_method) = true;
     }
 
@@ -390,9 +390,11 @@ message CreateVolumeRequest {
   // choose where the provisioned volume is accessible from.
   TopologyRequirement accessibility_requirements = 7;
 
-  // The ID of the volume group where the volume will be added to.
+  // The IDs of the volume groups where the volume will be added to.
+  // Note that it is possible for a volume to be placed in one or more
+  // groups on the storage backend even if this field is not specified.
   // This field is OPTIONAL.
-  string volume_group_id = 8;
+  repeated string volume_group_id = 8 [(alpha_field) = true];
 }
 
 // Specifies what source the volume will be created from. One of the
@@ -594,9 +596,11 @@ message Volume {
   // in the "region" "R1".
   repeated Topology accessible_topology = 5;
 
-  // The ID of the volume group where the volume belongs to.
+  // The IDs of the volume groups where the volume belongs to.
+  // Note that it is possible for a volume to be placed in one or more
+  // groups on the storage backend even if this field is not specified.
   // This field is OPTIONAL.
-  string volume_group_id = 6;
+  repeated string volume_group_id = 6 [(alpha_field) = true];
 }
 
 message TopologyRequirement {
@@ -1101,14 +1105,14 @@ message VolumeGroup {
 
   // Underlying volumes in this group. The same definition in CSI
   // Volume.
-  // This field is REQUIRED.
+  // This field is OPTIONAL.
   // To support the creation of an empty group, this list can be empty.
   // However, this field is not empty in the following cases:
   // - Response from ListVolumeGroups or ControllerGetVolumeGroup if the
   //   VolumeGroup is not empty.
-  // - Response from ModifyVolumeGroup if the VolumeGroup is not
-  //   empty after modification.
-  repeated .csi.v1.Volume volumes = 3;
+  // - Response from ModifyVolumeGroupMembership if the
+  //   VolumeGroup is not empty after modification.
+  repeated Volume volumes = 3;
 }
 message DeleteVolumeGroupRequest {
   option (alpha_message) = true;
@@ -1117,8 +1121,8 @@ message DeleteVolumeGroupRequest {
   // This field is REQUIRED.
   string volume_group_id = 1;
 
-  // Secrets required by plugin to complete volume group deletion
-  // request.
+  // Secrets required by plugin to complete volume group
+  // deletion request.
   // This field is OPTIONAL. Refer to the `Secrets Requirements`
   // section on how to use this field.
   map<string, string> secrets = 2 [(csi_secret) = true];
@@ -1128,7 +1132,7 @@ message DeleteVolumeGroupResponse {
   option (alpha_message) = true;
   // Intentionally empty.
 }
-message ModifyVolumeGroupRequest {
+message ModifyVolumeGroupMembershipRequest {
   option (alpha_message) = true;
 
   // The ID of the volume group to be modified.
@@ -1151,7 +1155,7 @@ message ModifyVolumeGroupRequest {
   map<string, string> secrets = 3 [(csi_secret) = true];
 }
 
-message ModifyVolumeGroupResponse {
+message ModifyVolumeGroupMembershipResponse {
   option (alpha_message) = true;
 
   // Contains all attributes of the modified volume group.
@@ -1240,14 +1244,17 @@ message CreateVolumeGroupSnapshotRequest {
   // take a group snapshot
   repeated string volume_ids = 3;
 
-  // secrets required for snapshot creation (pulled from
-  // VolumeSnapshotClass)
-  // This field is OPTIONAL.
+  // Secrets required by plugin to complete volume group snapshot
+  // creation request.
+  // This field is OPTIONAL. Refer to the `Secrets Requirements`
+  // section on how to use this field.
   map<string, string> secrets = 4 [(.csi.v1.csi_secret) = true];
 
-  // params passed from VolumeSnapshotClass
-  // This field is OPTIONAL.
+  // Plugin specific parameters passed in as opaque key-value pairs.
+  // This field is OPTIONAL. The Plugin is responsible for parsing and
+  // validating these parameters. COs will treat these as opaque.
   map<string, string> parameters = 5;
+
 }
 
 message CreateVolumeGroupSnapshotResponse {
@@ -1268,7 +1275,7 @@ message VolumeGroupSnapshot {
   // A list of snapshots created. Snapshot is the same
   // definition as Snapshot definition used in CSI.
   // This field is OPTIONAL.
-  repeated .csi.v1.Snapshot snapshots = 2;
+  repeated Snapshot snapshots = 2;
 
   // Identity information for the source volume group. Currently, only
   // support the case that source is volume group. This field is
@@ -1279,8 +1286,7 @@ message VolumeGroupSnapshot {
   // This field is REQUIRED.
   bool ready_to_use = 4;
 
-  // Timestamp when the point-in-time consistency group snapshot is
-  // taken.
+  // Timestamp when the volume group snapshot is taken.
   // This field is REQUIRED.
   .google.protobuf.Timestamp creation_time = 5;
 
@@ -1458,30 +1464,35 @@ message ControllerServiceCapability {
       // Indicates that the controller plugin supports adding an
       // existing volume to a volume group and removing a volume from
       // a volume group without deleting it.
-      VOLUME_GROUP_ADD_REMOVE_EXISTING_VOLUME = 15
+      MODIFY_VOLUME_GROUP_MEMBERSHIP = 15
+      [(alpha_enum_value) = true];
+
+      // Indicates that the controller plugin supports creating and
+      // deleting a volume group snapshot.
+      CREATE_DELETE_VOLUME_GROUP_SNAPSHOT = 16
       [(alpha_enum_value) = true];
 
       // Indicates whether the controller plugin supports creating a
       // volume from an individual volume snapshot if the volume
       // snapshot is part of a VolumeGroupSnapshot.
       // Use cases: selective restore, advanced recovery, etc.
-      INDIVIDUAL_SNAPSHOT_RESTORE = 16 [(alpha_enum_value) = true];
+      INDIVIDUAL_SNAPSHOT_RESTORE = 17 [(alpha_enum_value) = true];
 
       // Indicates that the controller plugin supports getting details
       // of a volume group.
-      GET_VOLUME_GROUP = 17 [(alpha_enum_value) = true];
+      GET_VOLUME_GROUP = 18 [(alpha_enum_value) = true];
 
       // Indicates that the controller plugin supports getting details
       // of a volume group snapshot.
-      GET_VOLUME_GROUP_SNAPSHOT = 18 [(alpha_enum_value) = true];
+      GET_VOLUME_GROUP_SNAPSHOT = 19 [(alpha_enum_value) = true];
 
       // Indicates that the controller plugin supports getting details
       // of a list of volume groups.
-      LIST_VOLUME_GROUPS = 19 [(alpha_enum_value) = true];
+      LIST_VOLUME_GROUPS = 20 [(alpha_enum_value) = true];
 
       // Indicates that the controller plugin supports getting details
       // of a list of volume group snapshots.
-      LIST_VOLUME_GROUP_SNAPSHOTS = 20 [(alpha_enum_value) = true];
+      LIST_VOLUME_GROUP_SNAPSHOTS = 21 [(alpha_enum_value) = true];
     }
 
     Type type = 1;