Load Chunks for Login Asynchronously

No longer will trigger Synchronous Chunk Loads when a player logs
in to the server.

Will delay PlayerJoinEvent until the chunk has been loaded.

Should have massive performance benefits for larger servers with
lots of players logging in and out.

Spigot-Server-Patches/0487-Load-Chunks-for-Login-Asynchronously.patch

@@ -0,0 +1,41 @@
+From 5bfa76db63cb31d5187548eea7b1cc94f3ab2c3e Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Sun, 19 Apr 2020 04:28:29 -0400
+Subject: [PATCH] Load Chunks for Login Asynchronously
+
+
+diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
+index e737381b3..83ceb3f99 100644
+--- a/src/main/java/net/minecraft/server/PlayerList.java
++++ b/src/main/java/net/minecraft/server/PlayerList.java
+@@ -106,8 +106,9 @@ public abstract class PlayerList {
+         // CraftBukkit start - Better rename detection
+         if (nbttagcompound != null && nbttagcompound.hasKey("bukkit")) {
+             NBTTagCompound bukkit = nbttagcompound.getCompound("bukkit");
+-            s = bukkit.hasKeyOfType("lastKnownName", 8) ? bukkit.getString("lastKnownName") : s;
++            s = bukkit.hasKeyOfType("lastKnownName", 8) ? bukkit.getString("lastKnownName") : s; // Diff below
+         }
++        String lastKnownName = s; // Paper
+         if (nbttagcompound == null) entityplayer.moveToSpawn(worldserver); // Paper - only move to spawn on first login, otherwise, stay where you are....
+         // CraftBukkit end
+ 
+@@ -132,6 +133,16 @@ public abstract class PlayerList {
+         entityplayer.setYawPitch(loc.getYaw(), loc.getPitch());
+         // Spigot end
+ 
++        // Paper start - async load spawn in chunk
++        WorldServer finalWorldserver = worldserver;
++        worldserver.getChunkProvider().getChunkAtAsynchronously(loc.getBlockX() >> 4, loc.getBlockZ() >> 4, true, (chunk -> {
++            if (networkmanager.isConnected()) {
++                postChunkLoadJoin(entityplayer, finalWorldserver, nbttagcompound, networkmanager, lastKnownName, networkmanager.getSocketAddress().toString());
++            }
++        }));
++    }
++    private void postChunkLoadJoin(EntityPlayer entityplayer, WorldServer worldserver, NBTTagCompound nbttagcompound, NetworkManager networkmanager, String s, String s1) {
++        // Paper end
+         // CraftBukkit - Moved message to after join
+         // PlayerList.LOGGER.info("{}[{}] logged in with entity id {} at ({}, {}, {})", entityplayer.getDisplayName().getString(), s1, entityplayer.getId(), entityplayer.locX(), entityplayer.locY(), entityplayer.locZ());
+         WorldData worlddata = worldserver.getWorldData();
+-- 
+2.25.1
+