Paper/patches/server/0274-Async-command-map-building.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Callahan <mr.callahhh@gmail.com>
Date: Wed, 8 Apr 2020 02:42:14 -0500
Subject: [PATCH] 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.

diff --git a/src/main/java/net/minecraft/commands/Commands.java b/src/main/java/net/minecraft/commands/Commands.java
index 2008fd542eaf1c2fac776ae1751c227a3b6dde4b..e812cc865baaa1ee03872f7969ee98600b82483b 100644
--- a/src/main/java/net/minecraft/commands/Commands.java
+++ b/src/main/java/net/minecraft/commands/Commands.java
@@ -455,6 +455,24 @@ public class Commands {
         if ( org.spigotmc.SpigotConfig.tabComplete < 0 ) return; // Spigot
         // CraftBukkit start
         // Register Vanilla commands into builtRoot as before
+        // Paper start - Perf: Async command map building
+        COMMAND_SENDING_POOL.execute(() -> {
+                this.sendAsync(player);
+        });
+    }
+
+    public static final java.util.concurrent.ThreadPoolExecutor COMMAND_SENDING_POOL = new java.util.concurrent.ThreadPoolExecutor(
+        0, 2, 60L, java.util.concurrent.TimeUnit.SECONDS,
+        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) {
+        // 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();
 
@@ -472,7 +490,14 @@ public class Commands {
         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);
 
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 13aa191235ac6bb1d00d89ae29c750595cc6be78..0f1a7b649d398a875b57746530242e3ced595bfd 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -944,6 +944,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         }
 
         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();