Async command map building

This adds a custom pool inorder to make sure that they are closed
without much though, as it doesn't matter if the client is not sent
commands if the server is restarting. Using the default async pool caused issues to arise
due to the shutdown logic generally being much later.

paper-server/patches/sources/net/minecraft/commands/Commands.java.patch

@@ -188,7 +188,7 @@
              }
          } else {
              callback.accept(executioncontext);
-@@ -377,11 +452,37 @@
+@@ -377,22 +452,77 @@
      }
  
      public void sendCommands(ServerPlayer player) {
@@ -196,6 +196,25 @@
 +        if ( org.spigotmc.SpigotConfig.tabComplete < 0 ) return; // Spigot
 +        // CraftBukkit start
 +        // Register Vanilla commands into builtRoot as before
++        // Paper start - Perf: Async command map building
++        // Copy root children to avoid concurrent modification during building
++        final Collection<CommandNode<CommandSourceStack>> commandNodes = new java.util.ArrayList<>(this.dispatcher.getRoot().getChildren());
++        COMMAND_SENDING_POOL.execute(() -> this.sendAsync(player, commandNodes));
++    }
++
++    // Fixed pool, but with discard policy
++    public static final java.util.concurrent.ExecutorService COMMAND_SENDING_POOL = new java.util.concurrent.ThreadPoolExecutor(
++        2, 2, 0, java.util.concurrent.TimeUnit.MILLISECONDS,
++        new java.util.concurrent.LinkedBlockingQueue<>(),
++        new com.google.common.util.concurrent.ThreadFactoryBuilder()
++            .setNameFormat("Paper Async Command Builder Thread Pool - %1$d")
++            .setUncaughtExceptionHandler(new net.minecraft.DefaultUncaughtExceptionHandlerWithName(net.minecraft.server.MinecraftServer.LOGGER))
++            .build(),
++        new java.util.concurrent.ThreadPoolExecutor.DiscardPolicy()
++    );
++
++    private void sendAsync(ServerPlayer player, Collection<CommandNode<CommandSourceStack>> dispatcherRootChildren) {
++        // Paper end - Perf: Async command map building
 +        Map<CommandNode<CommandSourceStack>, CommandNode<SharedSuggestionProvider>> map = Maps.newIdentityHashMap(); // Use identity to prevent aliasing issues
 +        RootCommandNode vanillaRoot = new RootCommandNode();
 +
@@ -207,13 +226,21 @@
          RootCommandNode<SharedSuggestionProvider> rootcommandnode = new RootCommandNode();
  
          map.put(this.dispatcher.getRoot(), rootcommandnode);
-         this.fillUsableCommands(this.dispatcher.getRoot(), rootcommandnode, player.createCommandSourceStack(), map);
+-        this.fillUsableCommands(this.dispatcher.getRoot(), rootcommandnode, player.createCommandSourceStack(), map);
++        this.fillUsableCommands(dispatcherRootChildren, rootcommandnode, player.createCommandSourceStack(), map); // Paper - Perf: Async command map building; pass copy of children
 +
 +        Collection<String> bukkit = new LinkedHashSet<>();
 +        for (CommandNode node : rootcommandnode.getChildren()) {
 +            bukkit.add(node.getName());
 +        }
++        // Paper start - Perf: Async command map building
++        net.minecraft.server.MinecraftServer.getServer().execute(() -> {
++           runSync(player, bukkit, rootcommandnode);
++        });
++    }
 +
++    private void runSync(ServerPlayer player, Collection<String> bukkit, RootCommandNode<SharedSuggestionProvider> rootcommandnode) {
++        // Paper end - Perf: Async command map building
 +        PlayerCommandSendEvent event = new PlayerCommandSendEvent(player.getBukkitEntity(), new LinkedHashSet<>(bukkit));
 +        event.getPlayer().getServer().getPluginManager().callEvent(event);
 +
@@ -227,7 +254,12 @@
          player.connection.send(new ClientboundCommandsPacket(rootcommandnode));
      }
  
-@@ -390,9 +491,10 @@
+-    private void fillUsableCommands(CommandNode<CommandSourceStack> tree, CommandNode<SharedSuggestionProvider> result, CommandSourceStack source, Map<CommandNode<CommandSourceStack>, CommandNode<SharedSuggestionProvider>> resultNodes) {
+-        Iterator iterator = tree.getChildren().iterator();
++    // Paper start - Perf: Async command map building; pass copy of children
++    private void fillUsableCommands(Collection<CommandNode<CommandSourceStack>> children, CommandNode<SharedSuggestionProvider> result, CommandSourceStack source, Map<CommandNode<CommandSourceStack>, CommandNode<SharedSuggestionProvider>> resultNodes) {
++        Iterator iterator = children.iterator();
++        // Paper end - Perf: Async command map building
  
          while (iterator.hasNext()) {
              CommandNode<CommandSourceStack> commandnode2 = (CommandNode) iterator.next();
@@ -239,7 +271,7 @@
  
                  argumentbuilder.requires((icompletionprovider) -> {
                      return true;
-@@ -415,7 +517,7 @@
+@@ -415,12 +545,12 @@
                      argumentbuilder.redirect((CommandNode) resultNodes.get(argumentbuilder.getRedirect()));
                  }
  
@@ -248,7 +280,13 @@
  
                  resultNodes.put(commandnode2, commandnode3);
                  result.addChild(commandnode3);
-@@ -481,7 +583,7 @@
+                 if (!commandnode2.getChildren().isEmpty()) {
+-                    this.fillUsableCommands(commandnode2, commandnode3, source, resultNodes);
++                    this.fillUsableCommands(commandnode2.getChildren(), commandnode3, source, resultNodes); // Paper - Perf: Async command map building; pass children directly
+                 }
+             }
+         }
+@@ -481,7 +611,7 @@
              }
  
              private <T> HolderLookup.RegistryLookup.Delegate<T> createLookup(final HolderLookup.RegistryLookup<T> original) {

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

@@ -690,7 +690,7 @@
          if (flush) {
              Iterator iterator1 = this.getAllLevels().iterator();
  
-@@ -628,18 +922,41 @@
+@@ -628,18 +922,42 @@
          this.stopServer();
      }
  
@@ -716,6 +716,7 @@
          }
  
          MinecraftServer.LOGGER.info("Stopping server");
++        Commands.COMMAND_SENDING_POOL.shutdownNow(); // Paper - Perf: Async command map building; Shutdown and don't bother finishing
 +        // CraftBukkit start
 +        if (this.server != null) {
 +            this.server.disablePlugins();
@@ -733,7 +734,7 @@
          }
  
          MinecraftServer.LOGGER.info("Saving worlds");
-@@ -693,6 +1010,15 @@
+@@ -693,6 +1011,15 @@
          } catch (IOException ioexception1) {
              MinecraftServer.LOGGER.error("Failed to unlock level {}", this.storageSource.getLevelId(), ioexception1);
          }
@@ -749,7 +750,7 @@
  
      }
  
-@@ -709,16 +1035,80 @@
+@@ -709,16 +1036,80 @@
      }
  
      public void halt(boolean waitForShutdown) {
@@ -830,7 +831,7 @@
  
      protected void runServer() {
          try {
-@@ -727,9 +1117,16 @@
+@@ -727,9 +1118,16 @@
              }
  
              this.nextTickTimeNanos = Util.getNanos();
@@ -848,7 +849,7 @@
              while (this.running) {
                  long i;
  
-@@ -744,12 +1141,31 @@
+@@ -744,12 +1142,31 @@
                      if (j > MinecraftServer.OVERLOADED_THRESHOLD_NANOS + 20L * i && this.nextTickTimeNanos - this.lastOverloadWarningNanos >= MinecraftServer.OVERLOADED_WARNING_INTERVAL_NANOS + 100L * i) {
                          long k = j / i;
  
@@ -880,7 +881,7 @@
                  boolean flag = i == 0L;
  
                  if (this.debugCommandProfilerDelayStart) {
-@@ -757,6 +1173,8 @@
+@@ -757,6 +1174,8 @@
                      this.debugCommandProfiler = new MinecraftServer.TimeProfiler(Util.getNanos(), this.tickCount);
                  }
  
@@ -889,7 +890,7 @@
                  this.nextTickTimeNanos += i;
  
                  try {
-@@ -830,6 +1248,13 @@
+@@ -830,6 +1249,13 @@
                      this.services.profileCache().clearExecutor();
                  }
  
@@ -903,7 +904,7 @@
                  this.onServerExit();
              }
  
-@@ -889,9 +1314,16 @@
+@@ -889,9 +1315,16 @@
      }
  
      private boolean haveTime() {
@@ -921,7 +922,7 @@
      public static boolean throwIfFatalException() {
          RuntimeException runtimeexception = (RuntimeException) MinecraftServer.fatalException.get();
  
-@@ -903,7 +1335,7 @@
+@@ -903,7 +1336,7 @@
      }
  
      public static void setFatalException(RuntimeException exception) {
@@ -930,7 +931,7 @@
      }
  
      @Override
-@@ -977,7 +1409,7 @@
+@@ -977,7 +1410,7 @@
          }
      }
  
@@ -939,7 +940,7 @@
          Profiler.get().incrementCounter("runTask");
          super.doRunTask(ticktask);
      }
-@@ -1025,6 +1457,7 @@
+@@ -1025,6 +1458,7 @@
      }
  
      public void tickServer(BooleanSupplier shouldKeepTicking) {
@@ -947,7 +948,7 @@
          long i = Util.getNanos();
          int j = this.pauseWhileEmptySeconds() * 20;
  
-@@ -1041,6 +1474,7 @@
+@@ -1041,6 +1475,7 @@
                      this.autoSave();
                  }
  
@@ -955,7 +956,7 @@
                  this.tickConnection();
                  return;
              }
-@@ -1055,12 +1489,13 @@
+@@ -1055,12 +1490,13 @@
          }
  
          --this.ticksUntilAutosave;
@@ -970,7 +971,7 @@
          gameprofilerfiller.push("tallying");
          long k = Util.getNanos() - i;
          int l = this.tickCount % 100;
-@@ -1074,7 +1509,7 @@
+@@ -1074,7 +1510,7 @@
      }
  
      private void autoSave() {
@@ -979,7 +980,7 @@
          MinecraftServer.LOGGER.debug("Autosave started");
          ProfilerFiller gameprofilerfiller = Profiler.get();
  
-@@ -1123,7 +1558,7 @@
+@@ -1123,7 +1559,7 @@
      private ServerStatus buildServerStatus() {
          ServerStatus.Players serverping_serverpingplayersample = this.buildPlayerStatus();
  
@@ -988,7 +989,7 @@
      }
  
      private ServerStatus.Players buildPlayerStatus() {
-@@ -1133,7 +1568,7 @@
+@@ -1133,7 +1569,7 @@
          if (this.hidesOnlinePlayers()) {
              return new ServerStatus.Players(i, list.size(), List.of());
          } else {
@@ -997,7 +998,7 @@
              ObjectArrayList<GameProfile> objectarraylist = new ObjectArrayList(j);
              int k = Mth.nextInt(this.random, 0, list.size() - j);
  
-@@ -1154,24 +1589,55 @@
+@@ -1154,24 +1590,55 @@
          this.getPlayerList().getPlayers().forEach((entityplayer) -> {
              entityplayer.connection.suspendFlushing();
          });
@@ -1053,7 +1054,7 @@
  
              gameprofilerfiller.push("tick");
  
-@@ -1186,6 +1652,7 @@
+@@ -1186,6 +1653,7 @@
  
              gameprofilerfiller.pop();
              gameprofilerfiller.pop();
@@ -1061,7 +1062,7 @@
          }
  
          gameprofilerfiller.popPush("connection");
-@@ -1265,8 +1732,24 @@
+@@ -1265,8 +1733,24 @@
      @Nullable
      public ServerLevel getLevel(ResourceKey<Level> key) {
          return (ServerLevel) this.levels.get(key);
@@ -1086,7 +1087,7 @@
      public Set<ResourceKey<Level>> levelKeys() {
          return this.levels.keySet();
      }
-@@ -1296,7 +1779,7 @@
+@@ -1296,7 +1780,7 @@
  
      @DontObfuscate
      public String getServerModName() {
@@ -1095,7 +1096,7 @@
      }
  
      public SystemReport fillSystemReport(SystemReport details) {
-@@ -1347,7 +1830,7 @@
+@@ -1347,7 +1831,7 @@
  
      @Override
      public void sendSystemMessage(Component message) {
@@ -1104,7 +1105,7 @@
      }
  
      public KeyPair getKeyPair() {
-@@ -1481,10 +1964,20 @@
+@@ -1481,10 +1965,20 @@
  
      @Override
      public String getMotd() {
@@ -1126,7 +1127,7 @@
          this.motd = motd;
      }
  
-@@ -1507,7 +2000,7 @@
+@@ -1507,7 +2001,7 @@
      }
  
      public ServerConnectionListener getConnection() {
@@ -1135,7 +1136,7 @@
      }
  
      public boolean isReady() {
-@@ -1634,11 +2127,11 @@
+@@ -1634,11 +2128,11 @@
  
      public CompletableFuture<Void> reloadResources(Collection<String> dataPacks) {
          CompletableFuture<Void> completablefuture = CompletableFuture.supplyAsync(() -> {
@@ -1149,7 +1150,7 @@
          }, this).thenCompose((immutablelist) -> {
              MultiPackResourceManager resourcemanager = new MultiPackResourceManager(PackType.SERVER_DATA, immutablelist);
              List<Registry.PendingTags<?>> list = TagLoader.loadTagsForExistingRegistries(resourcemanager, this.registries.compositeAccess());
-@@ -1654,6 +2147,7 @@
+@@ -1654,6 +2148,7 @@
          }).thenAcceptAsync((minecraftserver_reloadableresources) -> {
              this.resources.close();
              this.resources = minecraftserver_reloadableresources;
@@ -1157,7 +1158,7 @@
              this.packRepository.setSelected(dataPacks);
              WorldDataConfiguration worlddataconfiguration = new WorldDataConfiguration(MinecraftServer.getSelectedPacks(this.packRepository, true), this.worldData.enabledFeatures());
  
-@@ -1952,7 +2446,7 @@
+@@ -1952,7 +2447,7 @@
              final List<String> list = Lists.newArrayList();
              final GameRules gamerules = this.getGameRules();
  
@@ -1166,7 +1167,7 @@
                  @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 +2552,7 @@
+@@ -2058,7 +2553,7 @@
              try {
                  label51:
                  {
@@ -1175,7 +1176,7 @@
  
                      try {
                          arraylist = Lists.newArrayList(NativeModuleLister.listModules());
-@@ -2105,8 +2599,23 @@
+@@ -2105,8 +2600,23 @@
          if (bufferedwriter != null) {
              bufferedwriter.close();
          }
@@ -1199,7 +1200,7 @@
  
      private ProfilerFiller createProfiler() {
          if (this.willStartRecordingMetrics) {
-@@ -2225,18 +2734,24 @@
+@@ -2225,18 +2735,24 @@
      }
  
      public void logChatMessage(Component message, ChatType.Bound params, @Nullable String prefix) {