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, 39 insertions, 0 deletions

diff --git a/patches/server/0325-Configurable-projectile-relative-velocity.patch b/patches/server/0325-Configurable-projectile-relative-velocity.patch
new file mode 100644
index 0000000000..024876f999
--- /dev/null
+++ b/patches/server/0325-Configurable-projectile-relative-velocity.patch
@@ -0,0 +1,39 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Lucavon <[email protected]>
+Date: Tue, 23 Jul 2019 20:29:20 -0500
+Subject: [PATCH] Configurable projectile relative velocity
+
+This patch adds an option "disable relative projectile velocity", which, when
+enabled, will cause projectiles to ignore the shooter's current velocity,
+like they did in Minecraft 1.8 and prior.
+If a player is falling, for example, their shooting range will be drastically
+reduced, as a downwards velocity is applied to the projectile. This prevents
+players from saving themselves from falling off floating islands, for example,
+as a thrown ender pearl will not make it back to the island, while it would
+have in 1.8.
+
+While this could easily be done with plugins, too, there are multiple problems:
+P1) If multiple plugins cancel the velocity by subtracting the shooter's velocity
+from the projectile's velocity, the projectile's velocity would be different.
+As there's no way to detect whether the projectile's velocity has already been
+adjusted to ignore the player's velocity, plugins can't not do it if it's not
+necessary.
+P2) I've noticed some inconsistencies, e.g. weird velocity when shooting while
+using an elytra. Checking for those inconsistencies is possible, but not as
+efficient as just not applying the velocity in the first place.
+P3) Solutions for 1) and especially 2) might not be future-proof, while this
+server-internal fix makes this change future-proof.
+
+diff --git a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
+index 2dfe2e655026e6da1f548779ab3b455a6e42fb0c..66c3f374a779cd3a4548393ba23e9219f1caf6d3 100644
+--- a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
++++ b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
+@@ -161,7 +161,7 @@ public abstract class Projectile extends Entity {
+         this.shoot((double) f5, (double) f6, (double) f7, speed, divergence);
+         Vec3 vec3d = shooter.getDeltaMovement();
+ 
+-        this.setDeltaMovement(this.getDeltaMovement().add(vec3d.x, shooter.isOnGround() ? 0.0D : vec3d.y, vec3d.z));
++        if (!shooter.level.paperConfig().misc.disableRelativeProjectileVelocity) this.setDeltaMovement(this.getDeltaMovement().add(vec3d.x, shooter.isOnGround() ? 0.0D : vec3d.y, vec3d.z)); // Paper - allow disabling relative velocity
+     }
+ 
+     // CraftBukkit start - call projectile hit event