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, 43 insertions, 0 deletions

diff --git a/patches/server/0485-Extend-block-drop-capture-to-capture-all-items-added.patch b/patches/server/0485-Extend-block-drop-capture-to-capture-all-items-added.patch
new file mode 100644
index 0000000000..1517704ce1
--- /dev/null
+++ b/patches/server/0485-Extend-block-drop-capture-to-capture-all-items-added.patch
@@ -0,0 +1,43 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shane Freeder <[email protected]>
+Date: Thu, 17 Sep 2020 00:36:05 +0100
+Subject: [PATCH] Extend block drop capture to capture all items added to the
+ world
+
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index bcf74fc7ec97a4e8e0f78eecd64dd508841e080b..af06eb25172ff4ea3fdf2757ce17622e7f4075ae 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -1327,6 +1327,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
+             // WorldServer.LOGGER.warn("Tried to add entity {} but it was marked as removed already", EntityTypes.getKey(entity.getType())); // CraftBukkit
+             return false;
+         } else {
++            // Paper start - capture all item additions to the world
++            if (captureDrops != null && entity instanceof net.minecraft.world.entity.item.ItemEntity) {
++                captureDrops.add((net.minecraft.world.entity.item.ItemEntity) entity);
++                return true;
++            }
++            // Paper end
+             // SPIGOT-6415: Don't call spawn event when reason is null. For example when an entity teleports to a new world.
+             if (spawnReason != null && !CraftEventFactory.doEntityAddEventCalling(this, entity, spawnReason)) {
+                 return false;
+diff --git a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+index 431ff490760f54be76847c7b370dbbb4b65de102..1b45c1483a7ebad47162483b51036f9dfcdf62f6 100644
+--- a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
++++ b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+@@ -428,10 +428,12 @@ public class ServerPlayerGameMode {
+                     // return true; // CraftBukkit
+                 }
+                 // CraftBukkit start
++                java.util.List<net.minecraft.world.entity.item.ItemEntity> itemsToDrop = level.captureDrops; // Paper - store current list
++                level.captureDrops = null; // Paper - Remove this earlier so that we can actually drop stuff
+                 if (event.isDropItems()) {
+-                    org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockDropItemEvent(bblock, state, this.player, level.captureDrops);
++                    org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockDropItemEvent(bblock, state, this.player, itemsToDrop); // Paper - use stored ref
+                 }
+-                level.captureDrops = null;
++                //world.captureDrops = null; // Paper - move up
+ 
+                 // Drop event experience
+                 if (flag && event != null) {