Properly handle async calls to restart the server

The watchdog thread calls the server restart function asynchronously. Prior to
this change, it attempted to do several non-safe operations from the watchdog
thread, rather than the main. Specifically, because of a separate upstream change,
it causes player entities to be ticked asynchronously, among other things.

This is dangerous.

This patch moves the old handling into a synchronous variant, for calls from the
restart command, and adds separate handling for async calls, such as those from
the watchdog thread.

When calling from the watchdog thread, we cannot assume the main thread is in a
tickable state; it may be completely deadlocked. In order to handle this, we mark
the server as stopping, in order to account for situations where the server should
complete a tick reasonbly soon, i.e. 99% of cases.

Should the server not enter a state where it is stopping within 10 seconds, We
will assume that the server has in fact deadlocked and will proceed to force
kill the server.

This modification does not force restart the server should we actually enter a
deadlocked state where the server is stopping, whereas this will in most cases
exit within a reasonable amount of time, to put a fixed limit on a process that
will have plugins and worlds saving to the disk has a high potential to result
in corruption/dataloss.

paper-server/patches/sources/net/minecraft/server/MinecraftServer.java.patch

@@ -114,7 +114,15 @@
      private static final int OVERLOADED_TICKS_THRESHOLD = 20;
      private static final long OVERLOADED_WARNING_INTERVAL_NANOS = 10L * TimeUtil.NANOSECONDS_PER_SECOND;
      private static final int OVERLOADED_TICKS_WARNING_INTERVAL = 100;
-@@ -232,8 +255,7 @@
+@@ -224,6 +247,7 @@
+     private Map<ResourceKey<Level>, ServerLevel> levels;
+     private PlayerList playerList;
+     private volatile boolean running;
++    private volatile boolean isRestarting = false; // Paper - flag to signify we're attempting to restart
+     private boolean stopped;
+     private int tickCount;
+     private int ticksUntilAutosave;
+@@ -232,8 +256,7 @@
      private boolean preventProxyConnections;
      private boolean pvp;
      private boolean allowFlight;
@@ -124,7 +132,7 @@
      private int playerIdleTimeout;
      private final long[] tickTimesNanos;
      private long aggregatedTickTimesNanos;
-@@ -277,6 +299,26 @@
+@@ -277,6 +300,26 @@
      private final SuppressedExceptionCollector suppressedExceptions;
      private final DiscontinuousFrame tickFrame;
  
@@ -151,7 +159,7 @@
      public static <S extends MinecraftServer> S spin(Function<Thread, S> serverFactory) {
          AtomicReference<S> atomicreference = new AtomicReference();
          Thread thread = new Thread(() -> {
-@@ -290,15 +332,16 @@
+@@ -290,15 +333,16 @@
              thread.setPriority(8);
          }
  
@@ -170,7 +178,7 @@
          this.metricsRecorder = InactiveMetricsRecorder.INSTANCE;
          this.onMetricsRecordingStopped = (methodprofilerresults) -> {
              this.stopRecordingMetrics();
-@@ -319,36 +362,68 @@
+@@ -319,36 +363,68 @@
          this.scoreboard = new ServerScoreboard(this);
          this.customBossEvents = new CustomBossEvents();
          this.suppressedExceptions = new SuppressedExceptionCollector();
@@ -254,7 +262,7 @@
      }
  
      private void readScoreboard(DimensionDataStorage persistentStateManager) {
-@@ -357,7 +432,7 @@
+@@ -357,7 +433,7 @@
  
      protected abstract boolean initServer() throws IOException;
  
@@ -263,7 +271,7 @@
          if (!JvmProfiler.INSTANCE.isRunning()) {
              ;
          }
-@@ -365,12 +440,8 @@
+@@ -365,12 +441,8 @@
          boolean flag = false;
          ProfiledDuration profiledduration = JvmProfiler.INSTANCE.onWorldLoadedStarted();
  
@@ -277,7 +285,7 @@
          if (profiledduration != null) {
              profiledduration.finish(true);
          }
-@@ -387,23 +458,232 @@
+@@ -387,23 +459,232 @@
  
      protected void forceDifficulty() {}
  
@@ -524,7 +532,7 @@
  
          if (!iworlddataserver.isInitialized()) {
              try {
-@@ -427,30 +707,8 @@
+@@ -427,30 +708,8 @@
              iworlddataserver.setInitialized(true);
          }
  
@@ -556,7 +564,7 @@
  
      private static void setInitialSpawn(ServerLevel world, ServerLevelData worldProperties, boolean bonusChest, boolean debugWorld) {
          if (debugWorld) {
-@@ -458,6 +716,21 @@
+@@ -458,6 +717,21 @@
          } else {
              ServerChunkCache chunkproviderserver = world.getChunkSource();
              ChunkPos chunkcoordintpair = new ChunkPos(chunkproviderserver.randomState().sampler().findSpawnPosition());
@@ -578,7 +586,7 @@
              int i = chunkproviderserver.getGenerator().getSpawnHeight(world);
  
              if (i < world.getMinY()) {
-@@ -516,31 +789,36 @@
+@@ -516,31 +790,36 @@
          iworlddataserver.setGameType(GameType.SPECTATOR);
      }
  
@@ -626,7 +634,7 @@
              ForcedChunksSavedData forcedchunk = (ForcedChunksSavedData) worldserver1.getDataStorage().get(ForcedChunksSavedData.factory(), "chunks");
  
              if (forcedchunk != null) {
-@@ -555,10 +833,17 @@
+@@ -555,10 +834,17 @@
              }
          }
  
@@ -648,7 +656,7 @@
      }
  
      public GameType getDefaultGameType() {
-@@ -588,12 +873,16 @@
+@@ -588,12 +874,16 @@
              worldserver.save((ProgressListener) null, flush, worldserver.noSave && !force);
          }
  
@@ -667,7 +675,7 @@
          if (flush) {
              Iterator iterator1 = this.getAllLevels().iterator();
  
-@@ -628,18 +917,41 @@
+@@ -628,18 +918,41 @@
          this.stopServer();
      }
  
@@ -704,12 +712,13 @@
          if (this.playerList != null) {
              MinecraftServer.LOGGER.info("Saving players");
              this.playerList.saveAll();
-             this.playerList.removeAll();
+-            this.playerList.removeAll();
++            this.playerList.removeAll(this.isRestarting); // Paper
 +            try { Thread.sleep(100); } catch (InterruptedException ex) {} // CraftBukkit - SPIGOT-625 - give server at least a chance to send packets
          }
  
          MinecraftServer.LOGGER.info("Saving worlds");
-@@ -693,6 +1005,15 @@
+@@ -693,6 +1006,15 @@
          } catch (IOException ioexception1) {
              MinecraftServer.LOGGER.error("Failed to unlock level {}", this.storageSource.getLevelId(), ioexception1);
          }
@@ -725,7 +734,19 @@
  
      }
  
-@@ -715,10 +1036,68 @@
+@@ -709,16 +1031,80 @@
+     }
+ 
+     public void halt(boolean waitForShutdown) {
++        // Paper start - allow passing of the intent to restart
++        this.safeShutdown(waitForShutdown, false);
++    }
++    public void safeShutdown(boolean waitForShutdown, boolean isRestarting) {
++        this.isRestarting = isRestarting;
++        // Paper end
+         this.running = false;
+         if (waitForShutdown) {
+             try {
                  this.serverThread.join();
              } catch (InterruptedException interruptedexception) {
                  MinecraftServer.LOGGER.error("Error while shutting down", interruptedexception);
@@ -794,7 +815,7 @@
  
      protected void runServer() {
          try {
-@@ -727,9 +1106,15 @@
+@@ -727,9 +1113,15 @@
              }
  
              this.nextTickTimeNanos = Util.getNanos();
@@ -811,7 +832,7 @@
              while (this.running) {
                  long i;
  
-@@ -744,11 +1129,30 @@
+@@ -744,12 +1136,31 @@
                      if (j > MinecraftServer.OVERLOADED_THRESHOLD_NANOS + 20L * i && this.nextTickTimeNanos - this.lastOverloadWarningNanos >= MinecraftServer.OVERLOADED_WARNING_INTERVAL_NANOS + 100L * i) {
                          long k = j / i;
  
@@ -820,7 +841,7 @@
                          this.nextTickTimeNanos += k * i;
                          this.lastOverloadWarningNanos = this.nextTickTimeNanos;
                      }
-+                }
+                 }
 +                // Spigot start
 +                // Paper start - further improve server tick loop
 +                currentTime = Util.getNanos();
@@ -830,19 +851,20 @@
 +                    tps1.add(currentTps, diff);
 +                    tps5.add(currentTps, diff);
 +                    tps15.add(currentTps, diff);
-+
+ 
 +                    // Backwards compat with bad plugins
 +                    this.recentTps[0] = tps1.getAverage();
 +                    this.recentTps[1] = tps5.getAverage();
 +                    this.recentTps[2] = tps15.getAverage();
 +                    tickSection = currentTime;
-                 }
++                }
 +                // Paper end - further improve server tick loop
 +                // Spigot end
- 
++
                  boolean flag = i == 0L;
  
-@@ -757,6 +1161,8 @@
+                 if (this.debugCommandProfilerDelayStart) {
+@@ -757,6 +1168,8 @@
                      this.debugCommandProfiler = new MinecraftServer.TimeProfiler(Util.getNanos(), this.tickCount);
                  }
  
@@ -851,7 +873,7 @@
                  this.nextTickTimeNanos += i;
  
                  try {
-@@ -830,6 +1236,13 @@
+@@ -830,6 +1243,13 @@
                      this.services.profileCache().clearExecutor();
                  }
  
@@ -865,23 +887,25 @@
                  this.onServerExit();
              }
  
-@@ -889,7 +1302,14 @@
+@@ -889,9 +1309,16 @@
      }
  
      private boolean haveTime() {
 -        return this.runningTask() || Util.getNanos() < (this.mayHaveDelayedTasks ? this.delayedTasksMaxNextTickTimeNanos : this.nextTickTimeNanos);
 +        // CraftBukkit start
 +        return this.forceTicks || this.runningTask() || Util.getNanos() < (this.mayHaveDelayedTasks ? this.delayedTasksMaxNextTickTimeNanos : this.nextTickTimeNanos);
-+    }
+     }
-+
+ 
 +    private void executeModerately() {
 +        this.runAllTasks();
 +        java.util.concurrent.locks.LockSupport.parkNanos("executing tasks", 1000L);
 +        // CraftBukkit end
-     }
++    }
- 
++
      public static boolean throwIfFatalException() {
-@@ -903,7 +1323,7 @@
+         RuntimeException runtimeexception = (RuntimeException) MinecraftServer.fatalException.get();
+ 
+@@ -903,7 +1330,7 @@
      }
  
      public static void setFatalException(RuntimeException exception) {
@@ -890,7 +914,7 @@
      }
  
      @Override
-@@ -977,7 +1397,7 @@
+@@ -977,7 +1404,7 @@
          }
      }
  
@@ -899,7 +923,7 @@
          Profiler.get().incrementCounter("runTask");
          super.doRunTask(ticktask);
      }
-@@ -1025,6 +1445,7 @@
+@@ -1025,6 +1452,7 @@
      }
  
      public void tickServer(BooleanSupplier shouldKeepTicking) {
@@ -907,7 +931,7 @@
          long i = Util.getNanos();
          int j = this.pauseWhileEmptySeconds() * 20;
  
-@@ -1041,6 +1462,7 @@
+@@ -1041,6 +1469,7 @@
                      this.autoSave();
                  }
  
@@ -915,7 +939,7 @@
                  this.tickConnection();
                  return;
              }
-@@ -1055,12 +1477,13 @@
+@@ -1055,12 +1484,13 @@
          }
  
          --this.ticksUntilAutosave;
@@ -930,7 +954,7 @@
          gameprofilerfiller.push("tallying");
          long k = Util.getNanos() - i;
          int l = this.tickCount % 100;
-@@ -1074,7 +1497,7 @@
+@@ -1074,7 +1504,7 @@
      }
  
      private void autoSave() {
@@ -939,7 +963,7 @@
          MinecraftServer.LOGGER.debug("Autosave started");
          ProfilerFiller gameprofilerfiller = Profiler.get();
  
-@@ -1123,7 +1546,7 @@
+@@ -1123,7 +1553,7 @@
      private ServerStatus buildServerStatus() {
          ServerStatus.Players serverping_serverpingplayersample = this.buildPlayerStatus();
  
@@ -948,7 +972,7 @@
      }
  
      private ServerStatus.Players buildPlayerStatus() {
-@@ -1154,24 +1577,43 @@
+@@ -1154,24 +1584,43 @@
          this.getPlayerList().getPlayers().forEach((entityplayer) -> {
              entityplayer.connection.suspendFlushing();
          });
@@ -992,7 +1016,7 @@
  
              gameprofilerfiller.push("tick");
  
-@@ -1186,6 +1628,7 @@
+@@ -1186,6 +1635,7 @@
  
              gameprofilerfiller.pop();
              gameprofilerfiller.pop();
@@ -1000,12 +1024,10 @@
          }
  
          gameprofilerfiller.popPush("connection");
-@@ -1265,7 +1708,23 @@
+@@ -1267,6 +1717,22 @@
-     @Nullable
-     public ServerLevel getLevel(ResourceKey<Level> key) {
          return (ServerLevel) this.levels.get(key);
-+    }
+     }
-+
+ 
 +    // CraftBukkit start
 +    public void addLevel(ServerLevel level) {
 +        Map<ResourceKey<Level>, ServerLevel> oldLevels = this.levels;
@@ -1019,12 +1041,13 @@
 +        Map<ResourceKey<Level>, ServerLevel> newLevels = Maps.newLinkedHashMap(oldLevels);
 +        newLevels.remove(level.dimension());
 +        this.levels = Collections.unmodifiableMap(newLevels);
-     }
++    }
 +    // CraftBukkit end
- 
++
      public Set<ResourceKey<Level>> levelKeys() {
          return this.levels.keySet();
-@@ -1296,7 +1755,7 @@
+     }
+@@ -1296,7 +1762,7 @@
  
      @DontObfuscate
      public String getServerModName() {
@@ -1033,7 +1056,7 @@
      }
  
      public SystemReport fillSystemReport(SystemReport details) {
-@@ -1347,7 +1806,7 @@
+@@ -1347,7 +1813,7 @@
  
      @Override
      public void sendSystemMessage(Component message) {
@@ -1042,7 +1065,7 @@
      }
  
      public KeyPair getKeyPair() {
-@@ -1481,10 +1940,20 @@
+@@ -1481,10 +1947,20 @@
  
      @Override
      public String getMotd() {
@@ -1064,7 +1087,7 @@
          this.motd = motd;
      }
  
-@@ -1507,7 +1976,7 @@
+@@ -1507,7 +1983,7 @@
      }
  
      public ServerConnectionListener getConnection() {
@@ -1073,7 +1096,7 @@
      }
  
      public boolean isReady() {
-@@ -1634,11 +2103,11 @@
+@@ -1634,11 +2110,11 @@
  
      public CompletableFuture<Void> reloadResources(Collection<String> dataPacks) {
          CompletableFuture<Void> completablefuture = CompletableFuture.supplyAsync(() -> {
@@ -1087,7 +1110,7 @@
          }, this).thenCompose((immutablelist) -> {
              MultiPackResourceManager resourcemanager = new MultiPackResourceManager(PackType.SERVER_DATA, immutablelist);
              List<Registry.PendingTags<?>> list = TagLoader.loadTagsForExistingRegistries(resourcemanager, this.registries.compositeAccess());
-@@ -1654,6 +2123,7 @@
+@@ -1654,6 +2130,7 @@
          }).thenAcceptAsync((minecraftserver_reloadableresources) -> {
              this.resources.close();
              this.resources = minecraftserver_reloadableresources;
@@ -1095,7 +1118,7 @@
              this.packRepository.setSelected(dataPacks);
              WorldDataConfiguration worlddataconfiguration = new WorldDataConfiguration(MinecraftServer.getSelectedPacks(this.packRepository, true), this.worldData.enabledFeatures());
  
-@@ -1952,7 +2422,7 @@
+@@ -1952,7 +2429,7 @@
              final List<String> list = Lists.newArrayList();
              final GameRules gamerules = this.getGameRules();
  
@@ -1104,7 +1127,7 @@
                  @Override
                  public <T extends GameRules.Value<T>> void visit(GameRules.Key<T> key, GameRules.Type<T> type) {
                      list.add(String.format(Locale.ROOT, "%s=%s\n", key.getId(), gamerules.getRule(key)));
-@@ -2058,7 +2528,7 @@
+@@ -2058,7 +2535,7 @@
              try {
                  label51:
                  {
@@ -1113,7 +1136,7 @@
  
                      try {
                          arraylist = Lists.newArrayList(NativeModuleLister.listModules());
-@@ -2105,8 +2575,23 @@
+@@ -2105,8 +2582,23 @@
          if (bufferedwriter != null) {
              bufferedwriter.close();
          }
@@ -1137,7 +1160,7 @@
  
      private ProfilerFiller createProfiler() {
          if (this.willStartRecordingMetrics) {
-@@ -2225,18 +2710,24 @@
+@@ -2225,18 +2717,24 @@
      }
  
      public void logChatMessage(Component message, ChatType.Bound params, @Nullable String prefix) {

paper-server/patches/sources/net/minecraft/server/players/PlayerList.java.patch

@@ -729,14 +729,10 @@
              this.sendAllPlayerInfoIn = 0;
          }
  
-@@ -537,9 +832,28 @@
+@@ -541,6 +836,25 @@
-             ServerPlayer entityplayer = (ServerPlayer) iterator.next();
+ 
+     }
  
-             entityplayer.connection.send(packet);
-+        }
-+
-+    }
-+
 +    // CraftBukkit start - add a world/entity limited version
 +    public void broadcastAll(Packet packet, net.minecraft.world.entity.player.Player entityhuman) {
 +        for (int i = 0; i < this.players.size(); ++i) {
@@ -751,13 +747,14 @@
 +    public void broadcastAll(Packet packet, Level world) {
 +        for (int i = 0; i < world.players().size(); ++i) {
 +            ((ServerPlayer) world.players().get(i)).connection.send(packet);
-         }
++        }
- 
++
-     }
++    }
 +    // CraftBukkit end
- 
++
      public void broadcastAll(Packet<?> packet, ResourceKey<Level> dimension) {
          Iterator iterator = this.players.iterator();
+ 
 @@ -554,7 +868,7 @@
  
      }
@@ -880,14 +877,21 @@
      }
  
      public int getPlayerCount() {
-@@ -786,12 +1111,29 @@
+@@ -786,12 +1111,36 @@
      }
  
      public void removeAll() {
 -        for (int i = 0; i < this.players.size(); ++i) {
 -            ((ServerPlayer) this.players.get(i)).connection.disconnect((Component) Component.translatable("multiplayer.disconnect.server_shutdown"));
++        // Paper start - Extract method to allow for restarting flag
++        this.removeAll(false);
++    }
++
++    public void removeAll(boolean isRestarting) {
++        // Paper end
 +        // CraftBukkit start - disconnect safely
 +        for (ServerPlayer player : this.players) {
++            if (isRestarting) player.connection.disconnect(net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer.legacySection().deserialize(org.spigotmc.SpigotConfig.restartMessage)); else // Paper
 +            player.connection.disconnect(java.util.Objects.requireNonNullElseGet(this.server.server.shutdownMessage(), net.kyori.adventure.text.Component::empty)); // CraftBukkit - add custom shutdown message // Paper - Adventure
          }
 +        // CraftBukkit end
@@ -912,7 +916,7 @@
      public void broadcastSystemMessage(Component message, boolean overlay) {
          this.broadcastSystemMessage(message, (entityplayer) -> {
              return message;
-@@ -819,24 +1161,43 @@
+@@ -819,24 +1168,43 @@
      }
  
      public void broadcastChatMessage(PlayerChatMessage message, ServerPlayer sender, ChatType.Bound params) {
@@ -959,7 +963,7 @@
          }
  
          if (flag1 && sender != null) {
-@@ -845,20 +1206,27 @@
+@@ -845,20 +1213,27 @@
  
      }
  
@@ -992,7 +996,7 @@
                  Path path = file2.toPath();
  
                  if (FileUtil.isPathNormalized(path) && FileUtil.isPathPortable(path) && path.startsWith(file.getPath()) && file2.isFile()) {
-@@ -867,7 +1235,7 @@
+@@ -867,7 +1242,7 @@
              }
  
              serverstatisticmanager = new ServerStatsCounter(this.server, file1);
@@ -1001,7 +1005,7 @@
          }
  
          return serverstatisticmanager;
-@@ -875,13 +1243,13 @@
+@@ -875,13 +1250,13 @@
  
      public PlayerAdvancements getPlayerAdvancements(ServerPlayer player) {
          UUID uuid = player.getUUID();
@@ -1017,7 +1021,7 @@
          }
  
          advancementdataplayer.setPlayer(player);
-@@ -932,15 +1300,28 @@
+@@ -932,15 +1307,28 @@
      }
  
      public void reloadResources() {

paper-server/src/main/java/org/spigotmc/RestartCommand.java

@@ -46,86 +46,134 @@ public class RestartCommand extends Command
         AsyncCatcher.enabled = false; // Disable async catcher incase it interferes with us
         try
         {
-            String[] split = restartScript.split( " " );
+            // Paper - extract method and cleanup
-            if ( split.length > 0 && new File( split[0] ).isFile() )
+            boolean isRestarting = addShutdownHook( restartScript );
+            if ( isRestarting )
             {
-                System.out.println( "Attempting to restart with " + restartScript );
+                System.out.println( "Attempting to restart with " + SpigotConfig.restartScript );
-
-                // Disable Watchdog
-                WatchdogThread.doStop();
-
-                // Kick all players
-                for ( ServerPlayer p : (List<ServerPlayer>) MinecraftServer.getServer().getPlayerList().players )
-                {
-                    p.connection.disconnect( CraftChatMessage.fromStringOrEmpty( SpigotConfig.restartMessage, true ) );
-                }
-                // Give the socket a chance to send the packets
-                try
-                {
-                    Thread.sleep( 100 );
-                } catch ( InterruptedException ex )
-                {
-                }
-                // Close the socket so we can rebind with the new process
-                MinecraftServer.getServer().getConnection().stop();
-
-                // Give time for it to kick in
-                try
-                {
-                    Thread.sleep( 100 );
-                } catch ( InterruptedException ex )
-                {
-                }
-
-                // Actually shutdown
-                try
-                {
-                    MinecraftServer.getServer().close();
-                } catch ( Throwable t )
-                {
-                }
-
-                // This will be done AFTER the server has completely halted
-                Thread shutdownHook = new Thread()
-                {
-                    @Override
-                    public void run()
-                    {
-                        try
-                        {
-                            String os = System.getProperty( "os.name" ).toLowerCase(java.util.Locale.ENGLISH);
-                            if ( os.contains( "win" ) )
-                            {
-                                Runtime.getRuntime().exec( "cmd /c start " + restartScript );
-                            } else
-                            {
-                                Runtime.getRuntime().exec( "sh " + restartScript );
-                            }
-                        } catch ( Exception e )
-                        {
-                            e.printStackTrace();
-                        }
-                    }
-                };
-
-                shutdownHook.setDaemon( true );
-                Runtime.getRuntime().addShutdownHook( shutdownHook );
             } else
             {
                 System.out.println( "Startup script '" + SpigotConfig.restartScript + "' does not exist! Stopping server." );
-
-                // Actually shutdown
-                try
-                {
-                    MinecraftServer.getServer().close();
-                } catch ( Throwable t )
-                {
-                }
             }
-            System.exit( 0 );
+            // Stop the watchdog
+            WatchdogThread.doStop();
+
+            shutdownServer( isRestarting );
+            // Paper end
         } catch ( Exception ex )
         {
             ex.printStackTrace();
         }
     }
+
+    // Paper start - sync copied from above with minor changes, async added
+    private static void shutdownServer(boolean isRestarting)
+    {
+        if ( MinecraftServer.getServer().isSameThread() )
+        {
+            // Kick all players
+            for ( ServerPlayer p : com.google.common.collect.ImmutableList.copyOf( MinecraftServer.getServer().getPlayerList().players ) )
+            {
+                p.connection.disconnect( CraftChatMessage.fromStringOrEmpty( SpigotConfig.restartMessage, true ) );
+            }
+            // Give the socket a chance to send the packets
+            try
+            {
+                Thread.sleep( 100 );
+            } catch ( InterruptedException ex )
+            {
+            }
+
+            closeSocket();
+
+            // Actually shutdown
+            try
+            {
+                MinecraftServer.getServer().close(); // calls stop()
+            } catch ( Throwable t )
+            {
+            }
+
+            // Actually stop the JVM
+            System.exit( 0 );
+
+        } else
+        {
+            // Mark the server to shutdown at the end of the tick
+            MinecraftServer.getServer().safeShutdown( false, isRestarting );
+
+            // wait 10 seconds to see if we're actually going to try shutdown
+            try
+            {
+                Thread.sleep( 10000 );
+            }
+            catch (InterruptedException ignored)
+            {
+            }
+
+            // Check if we've actually hit a state where the server is going to safely shutdown
+            // if we have, let the server stop as usual
+            if (MinecraftServer.getServer().isStopped()) return;
+
+            // If the server hasn't stopped by now, assume worse case and kill
+            closeSocket();
+            System.exit( 0 );
+        }
+    }
+    // Paper end
+
+    // Paper - Split from moved code
+    private static void closeSocket()
+    {
+        // Close the socket so we can rebind with the new process
+        MinecraftServer.getServer().getConnection().stop();
+
+        // Give time for it to kick in
+        try
+        {
+            Thread.sleep( 100 );
+        } catch ( InterruptedException ex )
+        {
+        }
+    }
+    // Paper end
+
+    // Paper start - copied from above and modified to return if the hook registered
+    private static boolean addShutdownHook(String restartScript)
+    {
+        String[] split = restartScript.split( " " );
+        if ( split.length > 0 && new File( split[0] ).isFile() )
+        {
+            Thread shutdownHook = new Thread()
+            {
+                @Override
+                public void run()
+                {
+                    try
+                    {
+                        String os = System.getProperty( "os.name" ).toLowerCase(java.util.Locale.ENGLISH);
+                        if ( os.contains( "win" ) )
+                        {
+                            Runtime.getRuntime().exec( "cmd /c start " + restartScript );
+                        } else
+                        {
+                            Runtime.getRuntime().exec( "sh " + restartScript );
+                        }
+                    } catch ( Exception e )
+                    {
+                        e.printStackTrace();
+                    }
+                }
+            };
+
+            shutdownHook.setDaemon( true );
+            Runtime.getRuntime().addShutdownHook( shutdownHook );
+            return true;
+        } else
+        {
+            return false;
+        }
+    }
+    // Paper end
+
 }