From a5e3317e28cfef2718540166cac509696c4368d9 Mon Sep 17 00:00:00 2001
From: Audrius Butkevicius <audrius.butkevicius@gmail.com>
Date: Sat, 13 Sep 2014 15:25:39 +0100
Subject: [PATCH] Restart monitor as part of the upgrade process (fixes #682)

---
 cmd/syncthing/gui.go     |  4 +++-
 cmd/syncthing/main.go    |  1 +
 cmd/syncthing/monitor.go | 12 ++++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/cmd/syncthing/gui.go b/cmd/syncthing/gui.go
index e0afc7d3d..a3c015337 100644
--- a/cmd/syncthing/gui.go
+++ b/cmd/syncthing/gui.go
@@ -541,7 +541,9 @@ func restPostUpgrade(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
-		restPostRestart(w, r)
+		flushResponse(`{"ok": "restarting"}`, w)
+		l.Infoln("Upgrading")
+		stop <- exitUpgrading
 	}
 }
 
diff --git a/cmd/syncthing/main.go b/cmd/syncthing/main.go
index da577afd2..b980cbf7d 100644
--- a/cmd/syncthing/main.go
+++ b/cmd/syncthing/main.go
@@ -56,6 +56,7 @@ const (
 	exitError              = 1
 	exitNoUpgradeAvailable = 2
 	exitRestarting         = 3
+	exitUpgrading          = 4
 )
 
 var l = logger.DefaultLogger
diff --git a/cmd/syncthing/monitor.go b/cmd/syncthing/monitor.go
index ad8abddca..43582c989 100644
--- a/cmd/syncthing/monitor.go
+++ b/cmd/syncthing/monitor.go
@@ -91,6 +91,18 @@ func monitorMain() {
 			if err == nil {
 				// Successfull exit indicates an intentional shutdown
 				return
+			} else if exiterr, ok := err.(*exec.ExitError); ok {
+				if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
+					switch status.ExitStatus() {
+					case exitUpgrading:
+						// Restart the monitor process to release the .old
+						// binary as part of the upgrade process.
+						l.Infoln("Restarting monitor...")
+						os.Setenv("STNORESTART", "")
+						exec.Command(args[0], args[1:]...).Start()
+						return
+					}
+				}
 			}
 		}