Throw exception on world create while being ticked

There are no plans to support creating worlds while worlds are
being ticked themselvess.

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

@@ -150,7 +150,7 @@
      @Nullable
      private KeyPair keyPair;
      @Nullable
-@@ -277,6 +308,26 @@
+@@ -277,6 +308,27 @@
      private final SuppressedExceptionCollector suppressedExceptions;
      private final DiscontinuousFrame tickFrame;
  
@@ -173,11 +173,12 @@
 +    public final double[] recentTps = new double[ 3 ];
 +    // Spigot end
 +    public final io.papermc.paper.configuration.PaperConfigurations paperConfigurations; // Paper - add paper configuration files
++    public boolean isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
 +
      public static <S extends MinecraftServer> S spin(Function<Thread, S> serverFactory) {
          AtomicReference<S> atomicreference = new AtomicReference();
          Thread thread = new Thread(() -> {
-@@ -286,19 +337,21 @@
+@@ -286,19 +338,21 @@
          thread.setUncaughtExceptionHandler((thread1, throwable) -> {
              MinecraftServer.LOGGER.error("Uncaught exception in server thread", throwable);
          });
@@ -201,7 +202,7 @@
          this.metricsRecorder = InactiveMetricsRecorder.INSTANCE;
          this.onMetricsRecordingStopped = (methodprofilerresults) -> {
              this.stopRecordingMetrics();
-@@ -319,36 +372,68 @@
+@@ -319,36 +373,68 @@
          this.scoreboard = new ServerScoreboard(this);
          this.customBossEvents = new CustomBossEvents();
          this.suppressedExceptions = new SuppressedExceptionCollector();
@@ -285,7 +286,7 @@
      }
  
      private void readScoreboard(DimensionDataStorage persistentStateManager) {
-@@ -357,7 +442,7 @@
+@@ -357,7 +443,7 @@
  
      protected abstract boolean initServer() throws IOException;
  
@@ -294,7 +295,7 @@
          if (!JvmProfiler.INSTANCE.isRunning()) {
              ;
          }
-@@ -365,12 +450,8 @@
+@@ -365,12 +451,8 @@
          boolean flag = false;
          ProfiledDuration profiledduration = JvmProfiler.INSTANCE.onWorldLoadedStarted();
  
@@ -308,7 +309,7 @@
          if (profiledduration != null) {
              profiledduration.finish(true);
          }
-@@ -387,23 +468,241 @@
+@@ -387,23 +469,241 @@
  
      protected void forceDifficulty() {}
  
@@ -564,7 +565,7 @@
  
          if (!iworlddataserver.isInitialized()) {
              try {
-@@ -427,30 +726,8 @@
+@@ -427,30 +727,8 @@
              iworlddataserver.setInitialized(true);
          }
  
@@ -596,7 +597,7 @@
  
      private static void setInitialSpawn(ServerLevel world, ServerLevelData worldProperties, boolean bonusChest, boolean debugWorld) {
          if (debugWorld) {
-@@ -458,6 +735,21 @@
+@@ -458,6 +736,21 @@
          } else {
              ServerChunkCache chunkproviderserver = world.getChunkSource();
              ChunkPos chunkcoordintpair = new ChunkPos(chunkproviderserver.randomState().sampler().findSpawnPosition());
@@ -618,7 +619,7 @@
              int i = chunkproviderserver.getGenerator().getSpawnHeight(world);
  
              if (i < world.getMinY()) {
-@@ -516,31 +808,36 @@
+@@ -516,31 +809,36 @@
          iworlddataserver.setGameType(GameType.SPECTATOR);
      }
  
@@ -666,7 +667,7 @@
              ForcedChunksSavedData forcedchunk = (ForcedChunksSavedData) worldserver1.getDataStorage().get(ForcedChunksSavedData.factory(), "chunks");
  
              if (forcedchunk != null) {
-@@ -555,10 +852,17 @@
+@@ -555,10 +853,17 @@
              }
          }
  
@@ -688,7 +689,7 @@
      }
  
      public GameType getDefaultGameType() {
-@@ -588,12 +892,16 @@
+@@ -588,12 +893,16 @@
              worldserver.save((ProgressListener) null, flush, worldserver.noSave && !force);
          }
  
@@ -707,7 +708,7 @@
          if (flush) {
              Iterator iterator1 = this.getAllLevels().iterator();
  
-@@ -628,18 +936,45 @@
+@@ -628,18 +937,45 @@
          this.stopServer();
      }
  
@@ -754,7 +755,7 @@
          }
  
          MinecraftServer.LOGGER.info("Saving worlds");
-@@ -693,6 +1028,15 @@
+@@ -693,6 +1029,15 @@
          } catch (IOException ioexception1) {
              MinecraftServer.LOGGER.error("Failed to unlock level {}", this.storageSource.getLevelId(), ioexception1);
          }
@@ -770,7 +771,7 @@
  
      }
  
-@@ -709,6 +1053,14 @@
+@@ -709,6 +1054,14 @@
      }
  
      public void halt(boolean waitForShutdown) {
@@ -785,7 +786,7 @@
          this.running = false;
          if (waitForShutdown) {
              try {
-@@ -720,6 +1072,64 @@
+@@ -720,6 +1073,64 @@
  
      }
  
@@ -850,7 +851,7 @@
      protected void runServer() {
          try {
              if (!this.initServer()) {
-@@ -727,9 +1137,16 @@
+@@ -727,9 +1138,16 @@
              }
  
              this.nextTickTimeNanos = Util.getNanos();
@@ -868,7 +869,7 @@
              while (this.running) {
                  long i;
  
-@@ -744,11 +1161,30 @@
+@@ -744,12 +1162,31 @@
                      if (j > MinecraftServer.OVERLOADED_THRESHOLD_NANOS + 20L * i && this.nextTickTimeNanos - this.lastOverloadWarningNanos >= MinecraftServer.OVERLOADED_WARNING_INTERVAL_NANOS + 100L * i) {
                          long k = j / i;
  
@@ -887,7 +888,7 @@
 +                    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();
@@ -896,10 +897,11 @@
 +                }
 +                // Paper end - further improve server tick loop
 +                // Spigot end
- 
++
                  boolean flag = i == 0L;
  
-@@ -757,6 +1193,8 @@
+                 if (this.debugCommandProfilerDelayStart) {
+@@ -757,6 +1194,8 @@
                      this.debugCommandProfiler = new MinecraftServer.TimeProfiler(Util.getNanos(), this.tickCount);
                  }
  
@@ -908,7 +910,7 @@
                  this.nextTickTimeNanos += i;
  
                  try {
-@@ -830,6 +1268,13 @@
+@@ -830,6 +1269,13 @@
                      this.services.profileCache().clearExecutor();
                  }
  
@@ -922,7 +924,7 @@
                  this.onServerExit();
              }
  
-@@ -889,9 +1334,16 @@
+@@ -889,9 +1335,16 @@
      }
  
      private boolean haveTime() {
@@ -940,7 +942,7 @@
      public static boolean throwIfFatalException() {
          RuntimeException runtimeexception = (RuntimeException) MinecraftServer.fatalException.get();
  
-@@ -903,7 +1355,7 @@
+@@ -903,7 +1356,7 @@
      }
  
      public static void setFatalException(RuntimeException exception) {
@@ -949,7 +951,7 @@
      }
  
      @Override
-@@ -961,6 +1413,7 @@
+@@ -961,6 +1414,7 @@
          if (super.pollTask()) {
              return true;
          } else {
@@ -957,7 +959,7 @@
              if (this.tickRateManager.isSprinting() || this.haveTime()) {
                  Iterator iterator = this.getAllLevels().iterator();
  
-@@ -968,16 +1421,16 @@
+@@ -968,16 +1422,16 @@
                      ServerLevel worldserver = (ServerLevel) iterator.next();
  
                      if (worldserver.getChunkSource().pollTask()) {
@@ -977,7 +979,7 @@
          Profiler.get().incrementCounter("runTask");
          super.doRunTask(ticktask);
      }
-@@ -1025,6 +1478,7 @@
+@@ -1025,6 +1479,7 @@
      }
  
      public void tickServer(BooleanSupplier shouldKeepTicking) {
@@ -985,7 +987,7 @@
          long i = Util.getNanos();
          int j = this.pauseWhileEmptySeconds() * 20;
  
-@@ -1041,11 +1495,13 @@
+@@ -1041,11 +1496,13 @@
                      this.autoSave();
                  }
  
@@ -999,7 +1001,7 @@
          ++this.tickCount;
          this.tickRateManager.tick();
          this.tickChildren(shouldKeepTicking);
-@@ -1055,12 +1511,18 @@
+@@ -1055,12 +1512,18 @@
          }
  
          --this.ticksUntilAutosave;
@@ -1019,7 +1021,7 @@
          gameprofilerfiller.push("tallying");
          long k = Util.getNanos() - i;
          int l = this.tickCount % 100;
-@@ -1069,12 +1531,17 @@
+@@ -1069,12 +1532,17 @@
          this.aggregatedTickTimesNanos += k;
          this.tickTimesNanos[l] = k;
          this.smoothedTickTimeMillis = this.smoothedTickTimeMillis * 0.8F + (float) k / (float) TimeUtil.NANOSECONDS_PER_MILLISECOND * 0.19999999F;
@@ -1038,7 +1040,7 @@
          MinecraftServer.LOGGER.debug("Autosave started");
          ProfilerFiller gameprofilerfiller = Profiler.get();
  
-@@ -1123,7 +1590,7 @@
+@@ -1123,7 +1591,7 @@
      private ServerStatus buildServerStatus() {
          ServerStatus.Players serverping_serverpingplayersample = this.buildPlayerStatus();
  
@@ -1047,7 +1049,7 @@
      }
  
      private ServerStatus.Players buildPlayerStatus() {
-@@ -1133,7 +1600,7 @@
+@@ -1133,7 +1601,7 @@
          if (this.hidesOnlinePlayers()) {
              return new ServerStatus.Players(i, list.size(), List.of());
          } else {
@@ -1056,7 +1058,7 @@
              ObjectArrayList<GameProfile> objectarraylist = new ObjectArrayList(j);
              int k = Mth.nextInt(this.random, 0, list.size() - j);
  
-@@ -1154,24 +1621,56 @@
+@@ -1154,24 +1622,58 @@
          this.getPlayerList().getPlayers().forEach((entityplayer) -> {
              entityplayer.connection.suspendFlushing();
          });
@@ -1065,7 +1067,8 @@
          gameprofilerfiller.push("commandFunctions");
          this.getFunctions().tick();
          gameprofilerfiller.popPush("levels");
-         Iterator iterator = this.getAllLevels().iterator();
+-        Iterator iterator = this.getAllLevels().iterator();
++        //Iterator iterator = this.getAllLevels().iterator(); // Paper - Throw exception on world create while being ticked; moved down
  
 +        // CraftBukkit start
 +        // Run tasks that are waiting on processing
@@ -1093,6 +1096,8 @@
 +            }
 +        }
 +
++        this.isIteratingOverLevels = true; // Paper - Throw exception on world create while being ticked
++        Iterator iterator = this.getAllLevels().iterator(); // Paper - Throw exception on world create while being ticked; move down
          while (iterator.hasNext()) {
              ServerLevel worldserver = (ServerLevel) iterator.next();
 +            worldserver.hasPhysicsEvent = org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - BlockPhysicsEvent
@@ -1113,15 +1118,17 @@
  
              gameprofilerfiller.push("tick");
  
-@@ -1186,6 +1685,7 @@
+@@ -1186,7 +1688,9 @@
  
              gameprofilerfiller.pop();
              gameprofilerfiller.pop();
 +            worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions
          }
++        this.isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
  
          gameprofilerfiller.popPush("connection");
-@@ -1267,6 +1767,22 @@
+         this.tickConnection();
+@@ -1267,6 +1771,22 @@
          return (ServerLevel) this.levels.get(key);
      }
  
@@ -1144,7 +1151,7 @@
      public Set<ResourceKey<Level>> levelKeys() {
          return this.levels.keySet();
      }
-@@ -1296,7 +1812,7 @@
+@@ -1296,7 +1816,7 @@
  
      @DontObfuscate
      public String getServerModName() {
@@ -1153,7 +1160,7 @@
      }
  
      public SystemReport fillSystemReport(SystemReport details) {
-@@ -1347,7 +1863,7 @@
+@@ -1347,7 +1867,7 @@
  
      @Override
      public void sendSystemMessage(Component message) {
@@ -1162,7 +1169,7 @@
      }
  
      public KeyPair getKeyPair() {
-@@ -1385,11 +1901,14 @@
+@@ -1385,11 +1905,14 @@
          }
      }
  
@@ -1182,7 +1189,7 @@
          }
      }
  
-@@ -1403,7 +1922,7 @@
+@@ -1403,7 +1926,7 @@
          while (iterator.hasNext()) {
              ServerLevel worldserver = (ServerLevel) iterator.next();
  
@@ -1191,7 +1198,7 @@
          }
  
      }
-@@ -1481,10 +2000,20 @@
+@@ -1481,10 +2004,20 @@
  
      @Override
      public String getMotd() {
@@ -1213,7 +1220,7 @@
          this.motd = motd;
      }
  
-@@ -1507,7 +2036,7 @@
+@@ -1507,7 +2040,7 @@
      }
  
      public ServerConnectionListener getConnection() {
@@ -1222,7 +1229,7 @@
      }
  
      public boolean isReady() {
-@@ -1632,13 +2161,19 @@
+@@ -1632,13 +2165,19 @@
          return this.functionManager;
      }
  
@@ -1244,7 +1251,7 @@
          }, this).thenCompose((immutablelist) -> {
              MultiPackResourceManager resourcemanager = new MultiPackResourceManager(PackType.SERVER_DATA, immutablelist);
              List<Registry.PendingTags<?>> list = TagLoader.loadTagsForExistingRegistries(resourcemanager, this.registries.compositeAccess());
-@@ -1654,17 +2189,21 @@
+@@ -1654,17 +2193,21 @@
          }).thenAcceptAsync((minecraftserver_reloadableresources) -> {
              this.resources.close();
              this.resources = minecraftserver_reloadableresources;
@@ -1266,7 +1273,7 @@
          }, this);
  
          if (this.isSameThread()) {
-@@ -1789,14 +2328,15 @@
+@@ -1789,14 +2332,15 @@
          if (this.isEnforceWhitelist()) {
              PlayerList playerlist = source.getServer().getPlayerList();
              UserWhiteList whitelist = playerlist.getWhiteList();
@@ -1284,7 +1291,7 @@
                  }
              }
  
-@@ -1952,7 +2492,7 @@
+@@ -1952,7 +2496,7 @@
              final List<String> list = Lists.newArrayList();
              final GameRules gamerules = this.getGameRules();
  
@@ -1293,7 +1300,7 @@
                  @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 +2598,7 @@
+@@ -2058,7 +2602,7 @@
              try {
                  label51:
                  {
@@ -1302,19 +1309,22 @@
  
                      try {
                          arraylist = Lists.newArrayList(NativeModuleLister.listModules());
-@@ -2108,6 +2648,21 @@
+@@ -2105,9 +2649,24 @@
- 
+         if (bufferedwriter != null) {
-     }
+             bufferedwriter.close();
- 
+         }
++
++    }
++
 +    // CraftBukkit start
 +    public boolean isDebugging() {
 +        return false;
 +    }
-+
+ 
 +    public static MinecraftServer getServer() {
 +        return SERVER; // Paper
-+    }
+     }
-+
+ 
 +    @Deprecated
 +    public static RegistryAccess getDefaultRegistryAccess() {
 +        return CraftRegistry.getMinecraftRegistry();
@@ -1324,7 +1334,7 @@
      private ProfilerFiller createProfiler() {
          if (this.willStartRecordingMetrics) {
              this.metricsRecorder = ActiveMetricsRecorder.createStarted(new ServerMetricsSamplersProvider(Util.timeSource, this.isDedicatedServer()), Util.timeSource, Util.ioPool(), new MetricsPersister("server"), this.onMetricsRecordingStopped, (path) -> {
-@@ -2225,18 +2780,24 @@
+@@ -2225,18 +2784,24 @@
      }
  
      public void logChatMessage(Component message, ChatType.Bound params, @Nullable String prefix) {
@@ -1353,13 +1363,11 @@
      }
  
      public boolean logIPs() {
-@@ -2377,6 +2938,32 @@
+@@ -2379,4 +2944,30 @@
-     }
- 
      public static record ServerResourcePackInfo(UUID id, String url, String hash, boolean isRequired, @Nullable Component prompt) {
-+
-+    }
  
+     }
++
 +    // Paper start - Add tick times API and /mspt command
 +    public static class TickTimes {
 +        private final long[] times;
@@ -1383,6 +1391,6 @@
 +            }
 +            return ((double) total / (double) times.length) * 1.0E-6D;
 +        }
-     }
++    }
 +    // Paper end - Add tick times API and /mspt command
  }

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -919,6 +919,11 @@ public final class CraftServer implements Server {
         return new ArrayList<World>(this.worlds.values());
     }
 
+    @Override
+    public boolean isTickingWorlds() {
+        return console.isIteratingOverLevels;
+    }
+
     public DedicatedPlayerList getHandle() {
         return this.playerList;
     }
@@ -1182,6 +1187,7 @@ public final class CraftServer implements Server {
     @Override
     public World createWorld(WorldCreator creator) {
         Preconditions.checkState(this.console.getAllLevels().iterator().hasNext(), "Cannot create additional worlds on STARTUP");
+        //Preconditions.checkState(!this.console.isIteratingOverLevels, "Cannot create a world while worlds are being ticked"); // Paper - Cat - Temp disable. We'll see how this goes.
         Preconditions.checkArgument(creator != null, "WorldCreator cannot be null");
 
         String name = creator.name();
@@ -1358,6 +1364,7 @@ public final class CraftServer implements Server {
 
     @Override
     public boolean unloadWorld(World world, boolean save) {
+        //Preconditions.checkState(!this.console.isIteratingOverLevels, "Cannot unload a world while worlds are being ticked"); // Paper - Cat - Temp disable. We'll see how this goes.
         if (world == null) {
             return false;
         }