api: add gRPC definition for version endpoint.

api/api.proto

@@ -80,16 +80,30 @@ message DeletePasswordResp {
   bool not_found = 1;
 }
 
+// VersionReq is a request to fetch version info.
+message VersionReq {}
+
+// VersionResp holds the version info of components.
+message VersionResp {
+  // Semantic version of the server.
+  string server = 1;
+  // Numeric version of the API. It increases everytime a new call is added to the API.
+  // Clients should use this info to determine if the server supports specific features.
+  int32 api = 2;
+}
+
 // Dex represents the dex gRPC service.
 service Dex {
-  // CreateClient attempts to create the client.
+  // CreateClient creates a client.
   rpc CreateClient(CreateClientReq) returns (CreateClientResp) {};
-  // DeleteClient attempts to delete the provided client.
+  // DeleteClient deletes the provided client.
   rpc DeleteClient(DeleteClientReq) returns (DeleteClientResp) {};
-  // CreatePassword attempts to create the password.
+  // CreatePassword creates a password.
   rpc CreatePassword(CreatePasswordReq) returns (CreatePasswordResp) {};
-  // UpdatePassword attempts to modify existing password.
+  // UpdatePassword modifies existing password.
   rpc UpdatePassword(UpdatePasswordReq) returns (UpdatePasswordResp) {};
-  // DeletePassword attempts to delete the password.
+  // DeletePassword deletes the password.
   rpc DeletePassword(DeletePasswordReq) returns (DeletePasswordResp) {};
+  // GetVersion returns version information of the server.
+  rpc GetVersion(VersionReq) returns (VersionResp) {};
 }

server/api.go

@@ -10,8 +10,13 @@ import (
 
 	"github.com/coreos/dex/api"
 	"github.com/coreos/dex/storage"
+	"github.com/coreos/dex/version"
 )
 
+// apiVersion increases everytime a new call is added to the API. Clients should use this info
+// to determine if the server supports specific features.
+const apiVersion = 0
+
 // NewAPI returns a server which implements the gRPC API interface.
 func NewAPI(s storage.Storage) api.DexServer {
 	return dexAPI{s: s}
@@ -159,3 +164,10 @@ func (d dexAPI) DeletePassword(ctx context.Context, req *api.DeletePasswordReq)
 	return &api.DeletePasswordResp{}, nil
 
 }
+
+func (d dexAPI) GetVersion(ctx context.Context, req *api.VersionReq) (*api.VersionResp, error) {
+	return &api.VersionResp{
+		Server: version.Version,
+		Api:    apiVersion,
+	}, nil
+}