A list of plugins that I found out that causes issues with Parallel World Ticking.
This is not a full comprehensive list because I only use a few public plugins, most of the plugins I use on SparklyPower are made by myself.
The movement checks can crash the server due to concurrency issues (more below), disable them in the config.
[03:14:05] [serverlevel-tick-worker-8/ERROR]: THE SERVER IS GOING TO CRASH! - Thread serverlevel-tick-worker-8 failed main thread check: Cannot query another world's (world) chunk (25, 16) in a ServerLevelTickThread - Is tick thread? true; Is server level tick thread? true; Currently ticking level: ArenasPvP; Is iterating over levels? true; Are we going to hard throw? false
java.lang.Throwable: null
at net.minecraft.server.level.ServerChunkCache.getChunk(ServerChunkCache.java:272) ~[?:?]
at net.minecraft.world.level.Level.getChunk(Level.java:900) ~[?:?]
at net.minecraft.world.level.Level.getBlockState(Level.java:1175) ~[?:?]
at org.bukkit.craftbukkit.v1_20_R2.block.CraftBlock.getType(CraftBlock.java:238) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at fr.neatmonster.nocheatplus.compat.bukkit.BlockCacheBukkit.fetchTypeId(BlockCacheBukkit.java:52) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.map.BlockCache.getOrCreateNode(BlockCache.java:317) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.map.BlockCache.getType(BlockCache.java:379) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.map.BlockProperties.collectFlagsSimple(BlockProperties.java:4454) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.location.RichBoundsLocation.collectBlockFlags(RichBoundsLocation.java:1327) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.location.RichBoundsLocation.collectBlockFlags(RichBoundsLocation.java:1309) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.checks.moving.model.LocationData.setExtraProperties(LocationData.java:92) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.checks.moving.model.MoveData.setWithExtraProperties(MoveData.java:207) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.checks.moving.MovingData.resetPlayerPositions(MovingData.java:585) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.checks.moving.util.AuxMoving.resetPositionsAndMediumProperties(AuxMoving.java:116) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.checks.moving.MovingListener.onPlayerTeleportMonitor(MovingListener.java:1989) ~[NoCheatPlus.jar:?]
at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:580) ~[?:?]
at fr.neatmonster.nocheatplus.event.mini.MultiListenerRegistry$AutoListener.onEvent(MultiListenerRegistry.java:82) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.event.mini.MiniListenerNode.onEvent(MiniListenerNode.java:157) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.event.mini.EventRegistryBukkit$4.execute(EventRegistryBukkit.java:124) ~[NoCheatPlus.jar:?]
at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:77) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperEventManager.callEvent(PaperEventManager.java:54) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.callEvent(PaperPluginManagerImpl.java:126) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:615) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at org.bukkit.craftbukkit.v1_20_R2.entity.CraftPlayer.teleport(CraftPlayer.java:1354) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.craftbukkit.v1_20_R2.entity.CraftPlayer.teleport(CraftPlayer.java:1252) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at net.perfectdreams.dreamcore.utils.extensions.EntityExtensionsKt.teleportToServerSpawn(EntityExtensions.kt:13) ~[DreamCore-reobf.jar:?]
at net.perfectdreams.dreamcore.utils.extensions.EntityExtensionsKt.teleportToServerSpawnWithEffects(EntityExtensions.kt:20) ~[DreamCore-reobf.jar:?]
at net.perfectdreams.dreamcore.utils.extensions.EntityExtensionsKt.teleportToServerSpawnWithEffects$default(EntityExtensions.kt:19) ~[DreamCore-reobf.jar:?]
at net.perfectdreams.dreamxizum.utils.ArenaXizum.finishArena(ArenaXizum.kt:185) ~[DreamXizum-reobf.jar:?]
at net.perfectdreams.dreamxizum.listeners.XizumListener.onDeath(XizumListener.kt:55) ~[DreamXizum-reobf.jar:?]
at com.destroystokyo.paper.event.executor.asm.generated.GeneratedEventExecutor732.execute(Unknown Source) ~[?:?]
at org.bukkit.plugin.EventExecutor$2.execute(EventExecutor.java:77) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:77) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperEventManager.callEvent(PaperEventManager.java:54) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.callEvent(PaperPluginManagerImpl.java:126) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:615) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at org.bukkit.craftbukkit.v1_20_R2.event.CraftEventFactory.callPlayerDeathEvent(CraftEventFactory.java:984) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at net.minecraft.server.level.ServerPlayer.die(ServerPlayer.java:961) ~[?:?]
at net.minecraft.world.entity.LivingEntity.hurt(LivingEntity.java:1548) ~[?:?]
at net.minecraft.world.entity.player.Player.hurt(Player.java:973) ~[?:?]
at net.minecraft.server.level.ServerPlayer.hurt(ServerPlayer.java:1130) ~[?:?]
at net.minecraft.world.entity.projectile.AbstractArrow.onHitEntity(AbstractArrow.java:402) ~[?:?]
at net.minecraft.world.entity.projectile.Projectile.onHit(Projectile.java:206) ~[?:?]
at net.minecraft.world.entity.projectile.Projectile.preOnHit(Projectile.java:197) ~[?:?]
at net.minecraft.world.entity.projectile.AbstractArrow.preOnHit(AbstractArrow.java:296) ~[?:?]
at net.minecraft.world.entity.projectile.AbstractArrow.tick(AbstractArrow.java:232) ~[?:?]
at net.minecraft.world.entity.projectile.Arrow.tick(Arrow.java:112) ~[?:?]
at net.minecraft.server.level.ServerLevel.tickNonPassenger(ServerLevel.java:1392) ~[?:?]
at net.minecraft.world.level.Level.guardEntityTick(Level.java:1314) ~[?:?]
at net.minecraft.server.level.ServerLevel.lambda$tick$8(ServerLevel.java:906) ~[?:?]
at net.minecraft.world.level.entity.EntityTickList.forEach(EntityTickList.java:49) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:886) ~[?:?]
at net.minecraft.server.MinecraftServer.lambda$tickChildren$16(MinecraftServer.java:1600) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572) ~[?:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:317) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
at java.lang.Thread.run(Thread.java:1583) ~[?:?]
The Change Tracker also has a concurrency bug. NoCheatPlus uses setAccess to control which world is being used in BlockCacheBukkit. This is fine in a sequential ticking server, but in a parallel ticking server, there is a race condition where one server level tick thread changes the world to World1, then another thread changes the world to World2, then whoops, a crash happens!
This also breaks the movement checks above: While the movement checks do have synchronized in their methods, the falling block checks don't, and both use the same BlockCache instance (handled by setAccess).
To work around this, disable changetracker.active and changetracker.pistons.
I think that NoCheatPlus may have other concurrency issues too due to its use of setAccess around the code. In fact, I think that NoCheatPlus has the same issues in Folia too, even tho NoCheatPlus is marked as "Folia supported".
[03:35:04] [serverlevel-tick-worker-6/ERROR]: THE SERVER IS GOING TO CRASH! - Thread serverlevel-tick-worker-6 failed main thread check: Cannot query another world's (world) chunk (-817, -45) in a ServerLevelTickThread - Is tick thread? true; Is server level tick thread? true; Currently ticking level: Resources; Is iterating over levels? true; Are we going to hard throw? false
java.lang.Throwable: null
at net.minecraft.server.level.ServerChunkCache.getChunk(ServerChunkCache.java:272) ~[?:?]
at net.minecraft.world.level.Level.getChunk(Level.java:900) ~[?:?]
at net.minecraft.world.level.Level.getBlockState(Level.java:1175) ~[?:?]
at org.bukkit.craftbukkit.v1_20_R2.block.CraftBlock.getType(CraftBlock.java:238) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at fr.neatmonster.nocheatplus.compat.bukkit.BlockCacheBukkit.fetchTypeId(BlockCacheBukkit.java:52) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.map.BlockCache.getOrCreateNode(BlockCache.java:317) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.utilities.map.BlockCache.getOrCreateBlockCacheNode(BlockCache.java:442) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeTracker.addBlock(BlockChangeTracker.java:571) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeTracker.addBlocks(BlockChangeTracker.java:433) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeTracker.addBlocks(BlockChangeTracker.java:394) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeListener.onEntityChangeBlock(BlockChangeListener.java:300) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeListener.access$200(BlockChangeListener.java:56) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeListener$2.onEvent(BlockChangeListener.java:99) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.compat.blocks.changetracker.BlockChangeListener$2.onEvent(BlockChangeListener.java:93) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.event.mini.MiniListenerNode.onEvent(MiniListenerNode.java:157) ~[NoCheatPlus.jar:?]
at fr.neatmonster.nocheatplus.event.mini.EventRegistryBukkit$4.execute(EventRegistryBukkit.java:124) ~[NoCheatPlus.jar:?]
at co.aikar.timings.TimedEventExecutor.execute(TimedEventExecutor.java:77) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at io.papermc.paper.plugin.manager.PaperEventManager.callEvent(PaperEventManager.java:54) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.callEvent(PaperPluginManagerImpl.java:126) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:615) ~[sparklypaper-api-1.20.2-R0.1-SNAPSHOT.jar:?]
at org.bukkit.craftbukkit.v1_20_R2.event.CraftEventFactory.callEntityChangeBlockEvent(CraftEventFactory.java:1411) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at org.bukkit.craftbukkit.v1_20_R2.event.CraftEventFactory.callEntityChangeBlockEvent(CraftEventFactory.java:1403) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at net.minecraft.world.entity.item.FallingBlockEntity.fall(FallingBlockEntity.java:98) ~[?:?]
at net.minecraft.world.entity.item.FallingBlockEntity.fall(FallingBlockEntity.java:92) ~[?:?]
at net.minecraft.world.level.block.FallingBlock.tick(FallingBlock.java:37) ~[?:?]
at net.minecraft.world.level.block.state.BlockBehaviour$BlockStateBase.tick(BlockBehaviour.java:1205) ~[?:?]
at net.minecraft.server.level.ServerLevel.tickBlock(ServerLevel.java:1340) ~[?:?]
at net.minecraft.world.ticks.LevelTicks.runCollectedTicks(LevelTicks.java:197) ~[?:?]
at net.minecraft.world.ticks.LevelTicks.tick(LevelTicks.java:94) ~[?:?]
at net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:848) ~[?:?]
at net.minecraft.server.MinecraftServer.lambda$tickChildren$16(MinecraftServer.java:1600) ~[sparklypaper-1.20.2.jar:git-SparklyPaper-"049a8e5"]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572) ~[?:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:317) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
at java.lang.Thread.run(Thread.java:1583) ~[?:?]
If a player mounted on a Warden teleports to another world, the server crashes.
This is caused by MyPetORG/MyPet#1647 and can even cause issues in vanilla Paper. In vanilla Paper, instead of crashing the server, the player is teleported back to the Warden's location.
Fork that removes the affecting code: https://github.com/SparklyPower/MyPet
If a NPC with a sleeping trait is teleported to another world, the server crashes because Citizens attempts to query the NPC's "bed" when ticking the entity, and because the entity is in a whole different world... things explode.