The Bug:
The server sometimes freezes when attempting to locate structures or biomes that are far away.
On several occasions, when I attempted to locate a village using the "/locate" command, the server would freeze and then eventually crash. In my testing, this issue only appeared to occur with structures that are far away such as badlands mineshafts and villages of specific kinds, as I tried to reproduce this with other structures such as mansions and igloos without success.
A crash report regarding this has been attached and can be found below.
Stack Trace:
[^crash-2022-04-22_18.30.50-server.txt]
Description: Watching Server
java.lang.Error: Watchdog
at [email protected]/jdk.internal.misc.Unsafe.park(Native Method)
at [email protected]/java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:252)
at awo.bq(SourceFile:152)
at awo.c(SourceFile:142)
at aeo.a(SourceFile:139)
at cef.a(SourceFile:196)
at cei.a(SourceFile:156)
at cup.a(SourceFile:368)
at cup.a(SourceFile:347)
at cup.a(SourceFile:287)
at abs.a(SourceFile:52)
at abs.a(SourceFile:38)
at abs$$Lambda$3680/0x0000000801395b60.run(Unknown Source)
at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:263)
at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:177)
at dr.a(SourceFile:262)
at afi.a(SourceFile:1270)
at afi.a(SourceFile:1254)
at afi.a(SourceFile:1237)
at we.a(SourceFile:30)
at we.a(SourceFile:7)
at ry.a(SourceFile:22)
at ry$$Lambda$5081/0x0000000801777558.run(Unknown Source)
at aab.run(SourceFile:18)
at awo.d(SourceFile:157)
at aws.d(SourceFile:23)
at net.minecraft.server.MinecraftServer.b(SourceFile:782)
at net.minecraft.server.MinecraftServer.d(SourceFile:158)
at awo.x(SourceFile:131)
at net.minecraft.server.MinecraftServer.bf(SourceFile:764)
at net.minecraft.server.MinecraftServer.x(SourceFile:758)
at awo.bp(SourceFile:116)
at net.minecraft.server.MinecraftServer.w(SourceFile:742)
at net.minecraft.server.MinecraftServer.v(SourceFile:675)
at net.minecraft.server.MinecraftServer.a(SourceFile:263)
at net.minecraft.server.MinecraftServer$$Lambda$4253/0x000000080142d578.run(Unknown Source)
at [email protected]/java.lang.Thread.run(Thread.java:833)Steps to Reproduce:
Launch the latest snapshot of Minecraft and create a new world with cheats enabled.
Attempt to locate a savanna village by using the command provided below.
/locate structure minecraft:village_savannaIf the server didn't crash, teleport yourself a fair distance away from your current location and attempt to locate another village again by using the commands provided below.
/tp @s ~10000 ~ ~/locate structure minecraft:village_savannaTake note as to whether or not the server sometimes freezes when attempting to locate structures or biomes that are far away.
Observed Behavior:
The server freezes.
Expected Behavior:
The server would not freeze.
Linked issues
is duplicated by 19
MC-189880
/locate biome can cause large amounts of server lag if the specified biome is very rare or non-existant
Resolved
MC-190043
Bug / locatebiome mushroom fields
Resolved
MC-194318
Locate biome command causes lags in certain reasons
Resolved
MC-206306
/locatebiome command is extremely inefficient
Resolved
MC-206327
(Server) Using /locate in customized worlds on a structure that is very far away or doesn't exist freezes the game
Resolved
MC-212157
Glow Squids have an aneurism when you execute a faulty command
Resolved
MC-214172
Hello Mojang in the new snapshot you fixed some bugs but you have another bug that is game freeze
Resolved
MC-214530
Game freezes and stops responding when I do /locatebiome dripstone_caves
Resolved
MC-218833
Game lags after doing /locatebiome lush_caves
Resolved
MC-221992
When running /locatebiome command, singleplayer becomes unresponsive.
Resolved
MC-257701
Using the /locate directive causes the chunk to stop loading
Resolved
MC-261097
Woodland Mansion generation conditions are not configurable and lag /locate when not fulfilled
Resolved
MC-262028
Every blocks cannot interact after typing command /locate structure minecraft:snowy_village
Resolved
MC-264083
Mobs Freezes after I do /locate twice
Resolved
MC-264325
Loading structures when there are none causes lag
Resolved
MC-264464
Using /locate on a structure in a structureless void lags out game
Resolved
MC-264747
Leaving while /locate-ing causes your game to freeze.
Resolved
MC-271119
Locating structures in worlds without structures breaks the game
Resolved
MC-274760
Cartographer villager teporarily frezzes game
Resolved
relates to 3
MC-130449
Cartographer villager freezes or crashes the game when unlocking explorer maps
Resolved
MC-201704
Leveling up a Cartographer to Journeyman or searching for a Woodland Mansion, Nether Fossil, or End City with /locate causes a tick freeze in custom worlds with no terrain
Resolved
MC-249136
Freeze/server-side lag spike sometimes occurs when attempting to locate a buried treasure or opening/breaking a chest containing a map
Resolved
Attachments
Comments 13
Thank you @unknown for this information; I've updated this ticket accordingly. 🙂
Affects 1.19-pre1. (Also Mojang if you're revisiting the /locate implementation maybe take a look at MC-138887?)
This also happens very often with custom structures.
Further investigating concludes that this issue is not exclusive to villages; I also experienced this when attempting to locate a badlands (mesa) mineshaft. Since I'm the reporter of this ticket, I've made the appropriate changes to reflect this new information.
This also indeed appears to affect biomes as well as structures. This ticket has been updated accordingly to reflect this.
Supposedly fixed with MC-126244, this also happens with structure generation turned off. Locating a structure (maybe also happens with explorer maps) would completely freeze the server. On a multiplayer server, all clients would get disconnected due to a time out and wouldn't able to reconnect again.
Affects 1.19.4 prerelease 3. The game stops updating, and you can fall out of the world forever. When you try to close the world it just stays in saving world screen making you have to force quit the game.
In 23w32a
Affects the new pre release 1.20.2-pre 1. Had really bad lag spike when opening a cartographer when it tried to find a witch hut.
Here's the situation as of 24w04a, as far as I can tell.
In the past, extended server freezes (often leading to crashes on dedicated servers) could be caused by locating certain types of structures, most notably buried treasures (MC-249136), or by trying to locate a structure which does not exist nearby/in the current dimension. Both of these issues have now been fixed, so any lag from running the locate command will rarely last more than a few seconds- still significant enough to interfere with mining and combat, but not even close to triggering the watchdog on dedicated servers. As to whether optimizations to the core locate algorithm could further reduce the server hang time, I suspect* that some improvements could be made but that bringing the runtime below 0.05s (1 tick) 100% of the time is unrealistic. This being the case, unless Mojang has some other threshold of when server hangs form /locate constitute a bug, they should either:
Resolve this as Won't Fix, since the most egregious cases have been dealt with and no further improvements can be made without substantial changes; or,
Leave this open pending a rewrite of the command system which allows expensive commands like /locate to run on a separate thread and return their results/success at a later time or not at all. Of the existing commands, /locate is probably the only one that would use this functionality.
Personally I would recommend the latter. The locate algorithm is most often used in creative worlds and when generating structure maps, so the result and success values aren't really essential. I did once make an algorithm for a data pack which used the result value as part of a ray marching algorithm to locate and teleport the player to the nearest structure (the structure in question being an entry/exit portal in a custom dimension), and there are probably other niche applications for this value, but in the grand scheme of things safeguarding server performance is more important.
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*To my knowledge no one has analyzed the locate algorithm in detail and suggested efficiency improvements, but the existence of MC-138887 proves that it isn't perfect as is.
Can confirm for 1.21.3
Can confirm for 1.21.5
Avoma
I would reword this report if I were you; this is the server freezing (also happens in singleplayer), not crashing (not in singleplayer); the crashing is caused by watchdog, which is a forced crash if the server takes too long (and can be changed in the server.properties, even turned off).