Automatically pause server if no players connected. (#2465)

Robust.Server/BaseServer.cs

@@ -1,6 +1,6 @@
 using System;
 using System.IO;
-using System.Runtime;
+using System.Linq;
 using System.Threading;
 using Prometheus;
 using Robust.Server.Console;
@@ -20,6 +20,7 @@ using Robust.Shared;
 using Robust.Shared.Asynchronous;
 using Robust.Shared.Configuration;
 using Robust.Shared.ContentPack;
+using Robust.Shared.Enums;
 using Robust.Shared.Exceptions;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
@@ -94,6 +95,7 @@ namespace Robust.Server
         private Func<ILogHandler>? _logHandlerFactory;
         private ILogHandler? _logHandler;
         private IGameLoop _mainLoop = default!;
+        private bool _autoPause;
 
         private string? _shutdownReason;
 
@@ -319,7 +321,8 @@ namespace Robust.Server
             IoCManager.Resolve<IGameTiming>().InSimulation = true;
 
             IoCManager.Resolve<INetConfigurationManager>().SetupNetworking();
-            IoCManager.Resolve<IPlayerManager>().Initialize(MaxPlayers);
+            _playerManager.Initialize(MaxPlayers);
+            _playerManager.PlayerStatusChanged += OnPlayerStatusChanged;
             IoCManager.Resolve<IPlacementManager>().Initialize();
             IoCManager.Resolve<IViewVariablesHost>().Initialize();
 
@@ -490,7 +493,7 @@ namespace Robust.Server
             _mainLoop.Update += (sender, args) => { ServerUpTime.Set(_uptimeStopwatch.Elapsed.TotalSeconds); };
 
             // set GameLoop.Running to false to return from this function.
-            _time.Paused = false;
+            _time.Paused = _autoPause;
         }
 
         internal void FinishMainLoop()
@@ -543,6 +546,49 @@ namespace Robust.Server
             Logger.InfoS("srv", $"Name: {ServerName}");
             Logger.InfoS("srv", $"TickRate: {_time.TickRate}({_time.TickPeriod.TotalMilliseconds:0.00}ms)");
             Logger.InfoS("srv", $"Max players: {MaxPlayers}");
+
+            cfgMgr.OnValueChanged(CVars.GameAutoPauseEmpty, UpdateAutoPause, true);
+        }
+
+        private void UpdateAutoPause(bool doAutoPause)
+        {
+            _autoPause = doAutoPause;
+            if (doAutoPause)
+            {
+                if (!_time.Paused && CheckIfShouldAutoPause())
+                {
+                    Logger.DebugS("srv", "game.auto_pause_empty changed, pausing");
+                    _time.Paused = true;
+                }
+            }
+            else if (_time.Paused)
+            {
+                Logger.DebugS("srv", "game.auto_pause_empty changed, unpausing");
+                _time.Paused = false;
+            }
+        }
+
+        private void OnPlayerStatusChanged(object? sender, SessionStatusEventArgs e)
+        {
+            if (!_autoPause)
+                return;
+
+            if (e.NewStatus == SessionStatus.Connected && _time.Paused)
+            {
+                Logger.DebugS("srv", "Client connecting, unpausing automatically.");
+                _time.Paused = false;
+            }
+
+            if (e.NewStatus == SessionStatus.Disconnected && CheckIfShouldAutoPause())
+            {
+                Logger.DebugS("srv", "Last client disconnected, pausing automatically.");
+                _time.Paused = true;
+            }
+        }
+
+        private bool CheckIfShouldAutoPause()
+        {
+            return _playerManager.Sessions.All(s => s.Status == SessionStatus.Disconnected);
         }
 
         // called right before main loop returns, do all saving/cleanup in here
@@ -551,6 +597,7 @@ namespace Robust.Server
             _modLoader.Shutdown();
 
             _playerManager.Shutdown();
+            _playerManager.PlayerStatusChanged -= OnPlayerStatusChanged;
 
             // shut down networking, kicking all players.
             _network.Shutdown($"Server shutting down: {_shutdownReason}");

Robust.Shared/CVars.cs

@@ -479,6 +479,12 @@ namespace Robust.Shared
         public static readonly CVarDef<bool> GameDeleteEmptyGrids =
             CVarDef.Create("game.delete_empty_grids", true, CVar.ARCHIVE | CVar.SERVER);
 
+        /// <summary>
+        /// Automatically pause simulation if there are no players connected to the game server.
+        /// </summary>
+        public static readonly CVarDef<bool> GameAutoPauseEmpty =
+            CVarDef.Create("game.auto_pause_empty", true, CVar.SERVERONLY);
+
         /*
          * LOG
          */