Rewrite chunk system (#8177)

Patch documentation to come

Issues with the old system that are fixed now:
- World generation does not scale with cpu cores effectively.
- Relies on the main thread for scheduling and maintaining chunk state, dropping chunk load/generate rates at lower tps.
- Unreliable prioritisation of chunk gen/load calls that block the main thread.
- Shutdown logic is utterly unreliable, as it has to wait for all chunks to unload - is it guaranteed that the chunk system is in a state on shutdown that it can reliably do this? Watchdog shutdown also typically failed due to thread checks, which is now resolved.
- Saving of data is not unified (i.e can save chunk data without saving entity data, poses problems for desync if shutdown is really abnormal.
- Entities are not loaded with chunks. This caused quite a bit of headache for Chunk#getEntities API, but now the new chunk system loads entities with chunks so that they are ready whenever the chunk loads in. Effectively brings the behavior back to 1.16 era, but still storing entities in their own separate regionfiles.

The above list is not complete. The patch documentation will complete it.

New chunk system hard relies on starlight and dataconverter, and most importantly the new concurrent utilities in ConcurrentUtil.

Some of the old async chunk i/o interface (i.e the old file io thread reroutes _some_ calls to the new file io thread) is kept for plugin compat reasons. It will be removed in the next major version of minecraft.

The old legacy chunk system patches have been moved to the removed folder in case we need them again.

1 files changed, 87 insertions, 0 deletions

diff --git a/patches/server/0230-SkeletonHorse-Additions.patch b/patches/server/0230-SkeletonHorse-Additions.patch
new file mode 100644
index 0000000000..3cf3e54089
--- /dev/null
+++ b/patches/server/0230-SkeletonHorse-Additions.patch
@@ -0,0 +1,87 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: BillyGalbreath <[email protected]>
+Date: Fri, 27 Jul 2018 22:36:31 -0500
+Subject: [PATCH] SkeletonHorse Additions
+
+
+diff --git a/src/main/java/net/minecraft/world/entity/animal/horse/SkeletonTrapGoal.java b/src/main/java/net/minecraft/world/entity/animal/horse/SkeletonTrapGoal.java
+index 114352b9e8aeea7c728b6b58047e38e2530401a9..68887c1a475c119d061c8325136c5245011cdcbb 100644
+--- a/src/main/java/net/minecraft/world/entity/animal/horse/SkeletonTrapGoal.java
++++ b/src/main/java/net/minecraft/world/entity/animal/horse/SkeletonTrapGoal.java
+@@ -17,6 +17,7 @@ import net.minecraft.world.item.enchantment.EnchantmentHelper;
+ public class SkeletonTrapGoal extends Goal {
+ 
+     private final SkeletonHorse horse;
++    private java.util.List<org.bukkit.entity.HumanEntity> eligiblePlayers; // Paper
+ 
+     public SkeletonTrapGoal(SkeletonHorse skeletonHorse) {
+         this.horse = skeletonHorse;
+@@ -24,12 +25,13 @@ public class SkeletonTrapGoal extends Goal {
+ 
+     @Override
+     public boolean canUse() {
+-        return this.horse.level.hasNearbyAlivePlayer(this.horse.getX(), this.horse.getY(), this.horse.getZ(), 10.0D);
++        return !(eligiblePlayers = this.horse.level.findNearbyBukkitPlayers(this.horse.getX(), this.horse.getY(), this.horse.getZ(), 10.0D, false)).isEmpty(); // Paper
+     }
+ 
+     @Override
+     public void tick() {
+         ServerLevel worldserver = (ServerLevel) this.horse.level;
++        if (!new com.destroystokyo.paper.event.entity.SkeletonHorseTrapEvent((org.bukkit.entity.SkeletonHorse) this.horse.getBukkitEntity(), eligiblePlayers).callEvent()) return; // Paper
+         DifficultyInstance difficultydamagescaler = worldserver.getCurrentDifficultyAt(this.horse.blockPosition());
+ 
+         this.horse.setTrap(false);
+diff --git a/src/main/java/net/minecraft/world/level/EntityGetter.java b/src/main/java/net/minecraft/world/level/EntityGetter.java
+index be2ec73b5900354a9c340b0a03affd59dbf55377..c0817ef8927f00e2fd3fbf3289f8041fcb494049 100644
+--- a/src/main/java/net/minecraft/world/level/EntityGetter.java
++++ b/src/main/java/net/minecraft/world/level/EntityGetter.java
+@@ -100,6 +100,28 @@ public interface EntityGetter {
+         return player;
+     }
+ 
++    // Paper start
++    default List<org.bukkit.entity.HumanEntity> findNearbyBukkitPlayers(double x, double y, double z, double radius, boolean notSpectator) {
++        return findNearbyBukkitPlayers(x, y, z, radius, notSpectator ? EntitySelector.NO_SPECTATORS : net.minecraft.world.entity.EntitySelector.NO_CREATIVE_OR_SPECTATOR);
++    }
++
++    default List<org.bukkit.entity.HumanEntity> findNearbyBukkitPlayers(double x, double y, double z, double radius, @Nullable Predicate<Entity> predicate) {
++        com.google.common.collect.ImmutableList.Builder<org.bukkit.entity.HumanEntity> builder = com.google.common.collect.ImmutableList.builder();
++
++        for (Player human : this.players()) {
++            if (predicate == null || predicate.test(human)) {
++                double distanceSquared = human.distanceToSqr(x, y, z);
++
++                if (radius < 0.0D || distanceSquared < radius * radius) {
++                    builder.add(human.getBukkitEntity());
++                }
++            }
++        }
++
++        return builder.build();
++    }
++    // Paper end
++
+     @Nullable
+     default Player getNearestPlayer(Entity entity, double maxDistance) {
+         return this.getNearestPlayer(entity.getX(), entity.getY(), entity.getZ(), maxDistance, false);
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeletonHorse.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeletonHorse.java
+index e42dfd154f05130ff26f4d47d6817a1a561bfd54..78bc77d9cc5797fa8edd189167bb60b75b7f920e 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeletonHorse.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeletonHorse.java
+@@ -50,4 +50,16 @@ public class CraftSkeletonHorse extends CraftAbstractHorse implements SkeletonHo
+     public void setTrapTime(int trapTime) {
+         this.getHandle().trapTime = trapTime;
+     }
++
++    // Paper start - replaced by above methods
++    @Override
++    public boolean isTrap() {
++        return getHandle().isTrap();
++    }
++
++    @Override
++    public void setTrap(boolean trap) {
++        getHandle().setTrap(trap);
++    }
++    // Paper end
+ }