Add uptime to ServiceStatus (#3690)

cmd/admin-rpc-server.go

@@ -48,6 +48,12 @@ type ListLocksReply struct {
 	volLocks []VolumeLockInfo
 }
 
+// UptimeReply - wraps the uptime response over RPC.
+type UptimeReply struct {
+	AuthRPCReply
+	Uptime time.Duration
+}
+
 // Restart - Restart this instance of minio server.
 func (s *adminCmd) Restart(args *AuthRPCArgs, reply *AuthRPCReply) error {
 	if err := args.IsAuthenticated(); err != nil {
@@ -105,6 +111,27 @@ func (s *adminCmd) ReInitDisks(args *AuthRPCArgs, reply *AuthRPCReply) error {
 	return nil
 }
 
+// Uptime - returns the time when object layer was initialized on this server.
+func (s *adminCmd) Uptime(args *AuthRPCArgs, reply *UptimeReply) error {
+	if err := args.IsAuthenticated(); err != nil {
+		return err
+	}
+
+	if globalBootTime.IsZero() {
+		return errServerNotInitialized
+	}
+
+	// N B The uptime is computed assuming that the system time is
+	// monotonic. This is not the case in time pkg in Go, see
+	// https://github.com/golang/go/issues/12914. This is expected
+	// to be fixed by go1.9.
+	*reply = UptimeReply{
+		Uptime: time.Now().UTC().Sub(globalBootTime),
+	}
+
+	return nil
+}
+
 // registerAdminRPCRouter - registers RPC methods for service status,
 // stop and restart commands.
 func registerAdminRPCRouter(mux *router.Router) error {