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Remove wall-time / unused skip tick protection (#11412)

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Spigot still maintains some partial implementation of "tick skipping", a
practice in which the MinecraftServer.currentTick field is updated not
by an increment of one per actual tick, but instead set to
System.currentTimeMillis() / 50. This behaviour means that the tracked
tick may "skip" a tick value in case a previous tick took more than the
expected 50ms.

To compensate for this in important paths, spigot/craftbukkit
implements "wall-time". Instead of incrementing/decrementing ticks on
block entities/entities by one for each call to their tick() method,
they instead increment/decrement important values, like
an ItemEntity's age or pickupDelay, by the difference of
`currentTick - lastTick`, where `lastTick` is the value of
`currentTick` during the last tick() call.

These "fixes" however do not play nicely with minecraft's simulation
distance as entities/block entities implementing the above behaviour
would "catch up" their values when moving from a non-ticking chunk to a
ticking one as their `lastTick` value remains stuck on the last tick in
a ticking chunk and hence lead to a large "catch up" once ticked again.

Paper completely removes the "tick skipping" behaviour (See patch
"Further-improve-server-tick-loop"), making the above precautions
completely unnecessary, which also rids paper of the previous described
incompatibility with non-ticking chunks.
This commit is contained in:
Bjarne Koll 2024-09-19 16:36:07 +02:00 • committed by GitHub
parent 5c82955733
commit c5a10665b8
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GPG key ID: B5690EEEBB952194
794 changed files with 402 additions and 282 deletions
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90
patches/server/0300-Duplicate-UUID-Resolve-Option.patch Normal file
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@ -0,0 +1,90 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 21 Jul 2018 14:27:34 -0400
Subject: [PATCH] Duplicate UUID Resolve Option
Due to a bug in https://github.com/PaperMC/Paper/commit/2e29af3df05ec0a383f48be549d1c03200756d24
which was added all the way back in March of 2016, it was unknown (potentially not at the time)
that an entity might actually change the seed of the random object.
At some point, EntitySquid did start setting the seed. Due to this shared random, this caused
every entity to use a Random object with a predictable seed.
This has caused entities to potentially generate with the same UUID....
Over the years, servers have had entities disappear, but no sign of trouble
because CraftBukkit removed the log lines indicating that something was wrong.
We have fixed the root issue causing duplicate UUID's, however we now have chunk
files full of entities that have the same UUID as another entity!
When these chunks load, the 2nd entity will not be added to the world correctly.
If that chunk loads in a different order in the future, then it will reverse and the
missing one is now the one added to the world and not the other. This results in very
inconsistent entity behavior.
This change allows you to recover any duplicate entity by generating a new UUID for it.
This also lets you delete them instead if you don't want to risk having new entities added to
the world that you previously did not see.
But for those who are ok with leaving this inconsistent behavior, you may use WARN or NOTHING options.
It is recommended you regenerate the entities, as these were legit entities, and deserve your love.
diff --git a/src/main/java/net/minecraft/world/level/chunk/status/ChunkStatusTasks.java b/src/main/java/net/minecraft/world/level/chunk/status/ChunkStatusTasks.java
index 82fc5133325a127890984d51c1381883759eb444..ae16cf5c803caae636860dd9b1a83abe479ca5a4 100644
--- a/src/main/java/net/minecraft/world/level/chunk/status/ChunkStatusTasks.java
+++ b/src/main/java/net/minecraft/world/level/chunk/status/ChunkStatusTasks.java
@@ -189,10 +189,51 @@ public class ChunkStatusTasks {
entity.discard(null); // CraftBukkit - add Bukkit remove cause
needsRemoval = true;
}
+ checkDupeUUID(world, entity); // Paper - duplicate uuid resolving
return !needsRemoval;
}));
// CraftBukkit end
}
}
+
+ // Paper start - duplicate uuid resolving
+ // rets true if to prevent the entity from being added
+ public static boolean checkDupeUUID(ServerLevel level, net.minecraft.world.entity.Entity entity) {
+ io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode mode = level.paperConfig().entities.spawning.duplicateUuid.mode;
+ if (mode != io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode.WARN
+ && mode != io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode.DELETE
+ && mode != io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode.SAFE_REGEN) {
+ return false;
+ }
+ net.minecraft.world.entity.Entity other = level.getEntity(entity.getUUID());
+
+ if (other == null || other == entity) {
+ return false;
+ }
+
+ if (mode == io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode.SAFE_REGEN && other != null && !other.isRemoved()
+ && Objects.equals(other.getEncodeId(), entity.getEncodeId())
+ && entity.getBukkitEntity().getLocation().distance(other.getBukkitEntity().getLocation()) < level.paperConfig().entities.spawning.duplicateUuid.safeRegenDeleteRange
+ ) {
+ entity.discard(null);
+ return true;
+ }
+ if (!other.isRemoved()) {
+ switch (mode) {
+ case SAFE_REGEN: {
+ entity.setUUID(java.util.UUID.randomUUID());
+ break;
+ }
+ case DELETE: {
+ entity.discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.DISCARD);
+ return true;
+ }
+ default:
+ break;
+ }
+ }
+ return false;
+ }
+ // Paper end - duplicate uuid resolving
}