tools/oxenstored: Start live update process

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Reviewed-by: Pau Ruiz Safont <pau.safont@citrix.com>
Reviewed-by: Christian Lindig <christian.lindig@citrix.com>

tools/ocaml/xenstored/logging.ml

@@ -327,6 +327,9 @@ let end_transaction ~tid ~con =
 	if !access_log_transaction_ops && tid <> 0
 	then access_logging ~tid ~con (XbOp Xenbus.Xb.Op.Transaction_end) ~level:Debug
 
+let live_update () =
+	xb_op ~tid:0 ~con:"" ~ty:Xenbus.Xb.Op.Debug "Live update begin"
+
 let xb_answer ~tid ~con ~ty data =
 	let print, level = match ty with
 		| Xenbus.Xb.Op.Error when String.startswith "ENOENT" data -> !access_log_read_ops , Warn

tools/ocaml/xenstored/process.ml

@@ -111,6 +111,7 @@ let string_of_t t =
 let launch_exn t =
 	let executable, rest = args_of_t t in
 	let args = Array.of_list (executable :: rest) in
+	info "Launching %s, args: %s" executable (String.concat " " rest);
 	Unix.execv args.(0) args
 
 let validate_exn t =
@@ -147,7 +148,7 @@ let parse_live_update args =
 		| "-s" :: _ ->
 			let timeout = ref 60 in
 			let force = ref false in
-			Arg.parse_argv ~current:(ref 1) (Array.of_list args)
+			Arg.parse_argv ~current:(ref 0) (Array.of_list args)
 				[ ( "-t"
 				  , Arg.Set_int timeout
 				  , "timeout in seconds to wait for active transactions to finish"
@@ -197,7 +198,8 @@ let do_debug con t _domains cons data =
 	then None
 	else try match split None '\000' data with
 	| "live-update" :: params ->
-		LiveUpdate.parse_live_update params
+		let dropped_trailing_nul = params |> List.rev |> List.tl |> List.rev in
+		LiveUpdate.parse_live_update dropped_trailing_nul
 	| "print" :: msg :: _ ->
 		Logging.xb_op ~tid:0 ~ty:Xenbus.Xb.Op.Debug ~con:"=======>" msg;
 		None

tools/ocaml/xenstored/xenstored.ml

@@ -483,18 +483,29 @@ let _ =
 		in
 
 	Systemd.sd_notify_ready ();
+	let live_update = ref false in
 	while not (!quit && Connections.prevents_quit cons = [])
 	do
 		try
-			main_loop ()
+			main_loop ();
+			live_update := Process.LiveUpdate.should_run cons;
+			if !live_update || !quit then begin
+				(* don't initiate live update if saving state fails *)
+				DB.to_file store cons Disk.xs_daemon_database;
+				quit := true;
+			end
 		with exc ->
-			error "caught exception %s" (Printexc.to_string exc);
+			let bt = Printexc.get_backtrace () in
+			error "caught exception %s: %s" (Printexc.to_string exc) bt;
 			if cf.reraise_top_level then
 				raise exc
 	done;
 	info "stopping xenstored";
-	DB.to_file store cons Disk.xs_daemon_database;
 	(* unlink pidfile so that launch-xenstore works again *)
 	Unixext.unlink_safe pidfile;
 	(match cf.pidfile with Some pidfile -> Unixext.unlink_safe pidfile | None -> ());
-	()
+
+	if !live_update then begin
+		Logging.live_update ();
+		Process.LiveUpdate.launch_exn !Process.LiveUpdate.state
+	end