Server Crashes With a ConcurrentModificationException :(

Hey guys, I have been having a problem with my server crashing since updating to the latest RB. It seems to be pretty random, possibly when a player disconnects.

Code:

Unexpected exception
java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.next(Unknown Source)
at net.minecraft.server.World.tickEntities(World.java:1163)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:507)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)

This is the error that gets dumped to the log file. Looks like it has nothing to do with any plugins, it happens with the latest RB and 1615 which I am using at the moment. I suspected Spout and am using the latest dev version of the SpoutPlugin, it also happened with the latest RB.

looks like the same issue was reported here http://forums.bukkit.org/threads/cb-1531-server-hang-up-concurrentmodificationexception.47826/ too.

Anyone else seeing the same thing or have any idea how to stop it happening ?

 

This has to do with plugins. Some plugins are running asynchronous from the server and are having problems updating the world. Turn your plugins off and see what happens.

 

This is a dangerous error which kills your server's main thread; post your plugins and I'll see if I can recognize any suspicious ones.

 

This is the full list

• AutoMod
• ClassicAnimalSpawning
• CommandBook
• Help
• InfiniteLiquids
• InfinitePlots
• LogBlock
• LogBlockQuestioner
• mcbans
• ModTRS
• MSMHelper
• Multiverse-Core
• Multiverse-NetherPortals
• Multiverse-Portals
• NoCheat
• NoFloatingTrees
• OpenInv
• Permissions
• PermissionsBukkit
• PerWorldInventories
• RawcriticsOreObfuscationPluginSpout
• SimpleChestLock
• Simple Prefix
• SkylandsPlus
• SlotGroups
• Spout
• VanishNoPacket
• WorldEdit
• WorldGuard
• WorldRules

It only happens about once a day on average so very hard to test removing some. It hasn't happened since I downgraded Multiverse-NetherPortals and Multiverse-Portals to match the version of core but that could just be coincidence.

The only one of these that does anything to do with entities is ClassicAnimalSpawning which I wrote and is not released but that uses a sync task.

Slightly embarrassingly I just looked at my code for ClassicAnimalSpawning and it was using a async task so I guess that was the problem.

There is a lesson in all of this, typos can be dangerous.

Thanks for pointing me in the right direction anyway

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

I've had the same problem with one of my plugins before