Fix server update restarts when server paused. (#8509)

Content.Server/ServerUpdates/ServerUpdateManager.cs

@@ -0,0 +1,109 @@
+using System.Linq;
+using Content.Server.Chat.Managers;
+using Content.Shared.CCVar;
+using Robust.Server;
+using Robust.Server.Player;
+using Robust.Server.ServerStatus;
+using Robust.Shared.Configuration;
+using Robust.Shared.Enums;
+using Robust.Shared.Timing;
+
+namespace Content.Server.ServerUpdates;
+
+/// <summary>
+/// Responsible for restarting the server for update, when not disruptive.
+/// </summary>
+public sealed class ServerUpdateManager
+{
+    [Dependency] private readonly IGameTiming _gameTiming = default!;
+    [Dependency] private readonly IWatchdogApi _watchdog = default!;
+    [Dependency] private readonly IPlayerManager _playerManager = default!;
+    [Dependency] private readonly IChatManager _chatManager = default!;
+    [Dependency] private readonly IBaseServer _server = default!;
+    [Dependency] private readonly IConfigurationManager _cfg = default!;
+
+    [ViewVariables]
+    private bool _updateOnRoundEnd;
+
+    private TimeSpan? _restartTime;
+
+    public void Initialize()
+    {
+        _watchdog.UpdateReceived += WatchdogOnUpdateReceived;
+        _playerManager.PlayerStatusChanged += PlayerManagerOnPlayerStatusChanged;
+    }
+
+    public void Update()
+    {
+        if (_restartTime != null && _restartTime < _gameTiming.RealTime)
+        {
+            DoShutdown();
+        }
+    }
+
+    /// <summary>
+    /// Notify that the round just ended, which is a great time to restart if necessary!
+    /// </summary>
+    /// <returns>True if the server is going to restart.</returns>
+    public bool RoundEnded()
+    {
+        if (_updateOnRoundEnd)
+        {
+            DoShutdown();
+            return true;
+        }
+
+        return false;
+    }
+
+    private void PlayerManagerOnPlayerStatusChanged(object? sender, SessionStatusEventArgs e)
+    {
+        switch (e.NewStatus)
+        {
+            case SessionStatus.Connecting:
+                _restartTime = null;
+                break;
+            case SessionStatus.Disconnected:
+                ServerEmptyUpdateRestartCheck();
+                break;
+        }
+    }
+
+    private void WatchdogOnUpdateReceived()
+    {
+        _chatManager.DispatchServerAnnouncement(Loc.GetString("server-updates-received"));
+        _updateOnRoundEnd = true;
+        ServerEmptyUpdateRestartCheck();
+    }
+
+    /// <summary>
+    ///     Checks whether there are still players on the server,
+    /// and if not starts a timer to automatically reboot the server if an update is available.
+    /// </summary>
+    private void ServerEmptyUpdateRestartCheck()
+    {
+        // Can't simple check the current connected player count since that doesn't update
+        // before PlayerStatusChanged gets fired.
+        // So in the disconnect handler we'd still see a single player otherwise.
+        var playersOnline = _playerManager.Sessions.Any(p => p.Status != SessionStatus.Disconnected);
+        if (playersOnline || !_updateOnRoundEnd)
+        {
+            // Still somebody online.
+            return;
+        }
+
+        if (_restartTime != null)
+        {
+            // Do nothing because I guess we already have a timer running..?
+            return;
+        }
+
+        var restartDelay = TimeSpan.FromSeconds(_cfg.GetCVar(CCVars.UpdateRestartDelay));
+        _restartTime = restartDelay + _gameTiming.RealTime;
+    }
+
+    private void DoShutdown()
+    {
+        _server.Shutdown(Loc.GetString("server-updates-shutdown"));
+    }
+}