Mobs aren't spawning properly with 2+ players online.

We have an issue with mob spawning, in particular passive mobs but also hostiles as well. After the server's been up for a while and several people are on, there are no passive mobs to be found and hostile mob spawn rate drastically drops.

If I do a restart of the server and there's only 1 person on, passive and normal mobs spawn normally. They can travel around normally to our passive, hostile or slime grinder, or to any area and find a normal amount of mobs. By normal I mean if you travel through grassy areas you can generally see multiple groups of sheep/pigs/cows, and new groups spawn normally as you travel further away and the old mobs despawn (we tested by using dye on sheep). And the drop rate from the passive, hostile and slime grinder match what we get in a single-player copy of the map.

If a second person logs in, the spawn rate gradually decreases, and eventually is zero or nearly zero for passive mobs. There will also be a significant reduction in the number of hostile mobs -- very few hostiles will be found at night, very few or no ghasts, and the slime and hostile grinder have a major reduction in drop rate (1/10 of normal).

For example this is my passive grinder, there are no other grass chunks within 175+ blocks in all directions: http://i.imgur.com/859ks.png

In a single player map copy, or after a restart with only 1 person on, animals will constantly spawn. I have AFK'd here as the only player for 1+ hour of game time, as well as been the only player around and traveled extensively on the minecart network / nether portals and came back to the grinder with no change in behavior. If there is a second person online and they for example travel on the minecart network, then animals will no longer spawn at the grinder and will only very rarely spawn even in the largest grassy areas, as seen by the entity count via F3 debug screen. Our hostile mob grinder will drop from having 100+ mobs inside to 10-20 max.

Furthermore. We have tried having 2 people log in after a restart, and travel along the minecart system at night to spawn hostiles in unlit areas. If we then travel back during the day, large numbers of burning skeletons and zombies can be seen in chunks that should have been unloaded and hence those mobs should have despawned (AFAIK).


I think this means that chunks are not being unloaded properly when multiple players are online, but I'm not sure what could be causing such behavior. It's my understanding that if multiple people are online then the spawn rate is reduced (as the spawn cap is split between them), however I don't think the spawn rate should drop so drastically with only 2 players online. Help?



Linux 2.6.39.1-linode34 #1 SMP Tue Jun 21 10:29:24 EDT 2011 i686 GNU/Linux

java version "1.6.0_20"
OpenJDK Runtime Environment (IcedTea6 1.9.8) (6b20-1.9.8-0ubuntu1~10.04.1)
OpenJDK Client VM (build 19.0-b09, mixed mode, sharing)

java -Xmx640M -Xincgc -Xnoclassgc -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalPacing -XXarallelGCThreads=4 -XX:+AggressiveOpts -server -jar craftbukkit-0.0.1-SNAPSHOT.jar nogui

Bukkit build #1000, no wrappers. Tests were done with no plugins and view distance is set to 10 in server.properties.

 

Well this is a intresting one, I dont have a clue myself but I want to keep an eye on this one. Possibly a Bukkit 1000 issue?

 

I have sameproblem

 

I also have that issue, and it is very annoying...

 

same issue here, and when i try and spawn mobs they dissapear in like 30secs, running 1060