Entity Mass Spawning near chunk error

I was playing a map by Hypixel, when suddenly a good several hundred bats spawned in the dark space under the map (out of bounds for gameplay purposes; this isn't something Hypixel would do on purpose). Nobody else has said it happened to them, and I have found no evidence of bat spawners in the entire map. Also, the event did not repeat when starting from a fresh copy of the map, even when repeating my actions practically the same way. The map in question is Herobrine's Mansion, but that should largely be irrelevant: I've heard on the wiki of hundreds of bats spawning this way in singleplayer.

Even if, by some unlikely chance, this bat issue is "not a bug", in the same way that squid spawn in massive packs in new chunks, it should still be addressed by putting a cap on how many can spawn at once; at first my Minecraft crashed and I had to use MCedit to determine that there were hundreds of bats in one area.

But I think it's more likely that my issues with the bats are related to everyone else's sudden excessive mob explosions. I should mention that I was playing in singleplayer when this happened, but it seems unlikely for a bug of this nature to be limited to SMP anyhow, considering SSP is a local server (SMP-specific bugs usually rely on issues between the client and the server - but the sheep in this report are actual entities, else there wouldn't be any server crashes).

This is still a problem in 1.5. My world spawned several thousand chickens and eggs and has made my world completely unplayable, even after removing the entities and deleting the chunks in MCedit. I had had some problems with the same issue in 1.4.7 but unfortunately 1.5 did not fix it.

This recently happened to me after upgrading to 1.5. The issue has appeared twice, the first time 9600 sheep we're inside a small area. The second time it was 5000+ skeletons and 1000 other passive mods.

Can the title be changed to make it clear that this bug causes crashes?

Gerrard, I changed the title for you. Is that how you wanted it to explain?

Yes, that looks good. Mojang tends to put crash bugs on higher priority (as they should), so I figure this will help.

happened to me too, i was playing in multiplayer in an hunger game server, then my fps istant dropped to 0, i think this is the problem

https://twitter.com/Dinnerbone/status/331076749150523392

Tails, the funny part of this though, is that we deleted and reloaded the chunk using MCEdit, and the problem still persisted. Wouldn't reloading the chunk help towards corrupted chunks?

Lol i just found out this bug existed, suddenly there were like 500 ocelots that had spawned inside my farm. rly weird, lost all my chickens but got enough ocelots to scare a gaint creeper away 😛

ps. can anyone tell me how to prevent my world from crashing due to an overload of ocelots? right now i can still play, but if this continues, minecraft will probably crash.

I have same issue with ocelots. For me switching back to snapshot 13w17a fixes the problem, ocelots despawn with time, switching to 13w18abc makes them spawn in large numbers again.

Reopened MC-15173 as the ocelot mass spawning is a different issue after all.

People who have this issue with something other than ocelots (since that is a separate issue) should upload a copy of their world (or a small enough subset of their world that still shows the issue). Since this is likely some kind of corruption knowing what is corrupted and how would be extremely helpful for fixing it.

I have this issue with sheep, near a chunk that won't load. I tried to set them on fire, but they are not flammable enough. Slows to a crawl when nearby.

If you're having this issue with anything other than Ocelots, a world upload would give me somewhere to start with looking into this issue. Until then, there's not much I can do as I'm unable to come up with a way to reproduce this issue on demand.

I should've uploaded the world files back when I originally posted about this back in December. As of right now, I don't have it, but I'm gonna ask some of the server folks to see if anyone still has a copy of the world.

EDIT: We have not had this issue since that time though, if we do get it in the end, I will make sure to upload a world file with the approximate coordinates of the issue.

if you make a superflat world with only air and use a third party editor to place blocks you will get mass spawns

That's different, as it's caused by the game trying to meet a "quota" of passive and hostile mobs. It's the same reason Endermen grinders in the End work so well.

This bug causes entities to continue spawning, hundreds of times higher than their quotas/caps.

I haven't seen a world upload yet, so while this is a single player world, here's mine with this bug. I think the zip works, but if not, please direct me to somewhere I can learn how to submit the world.

Thank you, Mike. That should help in some way.

Doesn't really matter if it's singleplayer, since SP is basically a "server" running anyways.

@Mike Hultquist: Your ZIP file doesn't work, the subfolders (data, region, players,...) are missing.

That's about 100 MB, so how should I send them?

Can you put the file on a third party file hoster and provide the link here ?

This has the full world folder. If you need a different one, I can try a different host.

http://d-h.st/unX

@Mike Hultquist:
After deleting several thousands of sheep with MCEdit that world was usable. Besides your "sheep farm" there is a chunk error (see my screenshot, also visible in your screenshot), probably that is the cause for the mass spawning. The (client) console got spammed with "wrong location" messages.

I reported another bug about a chunk reverting to a previous saved configuration, after making changes to the chunk, and I think that may be related to this issue, because I went into MCEdit to look at the chunk where the sheep were spamspawning, and the chunk that wouldn't load in game, did not appear as the unloaded chunk but appeared as the chunk that kept reverting to previous condition on me. The reverting chunk is a few chunks away.

I will find the other open issue [MC-4001], and also attempt to upload the roughly 90 MB in the folder of the affected world.

Tails was Mod on MC-4001. Again, I think my spamspawn issue is symptomatic of the chunk error in MC-4001.

I have a world to upload, but I am unsure how to do that. The folder size for my world is about 90-100 MB.

Let me know how I can get you a copy, and I will do it. I may need to find a place to access it online.

EDIT: The location to find the folder with all world data for the affected world, is http://www.math.uiowa.edu/MathTutorialLab/oldpage/JIRA/

You will find a folder called Moose Town, that is the world name.

Happened to me in a worst case,when loading a world it freeze.I written more information in MC-2545

Still exists in the most recent 1.6.2 and launcher.

Here's my world:http://www.mediafire.com/download/j8sl6687xo4xg8s/Rauliux_Villager_Corrupted.rar

So can this be fixed by using MCEdit and finding the chunk error then deleting it?

Aaron, I believe we tried that, but with no luck. Although, it's a while ago, so I'm not really sure about that.

I have a bad chunk in the nether and sometimes when entering the dimension zombie pigman start raining inside the chunk, FPS drop to 2, all normal mobs (outside the chunk error) freeze and minecarts/buttons/etc. became unusable, after a few minutes the game crashes and, upon reloading, everything is back to normal with the empty chunk but no zombie pigman rain.
I've seen it in 1.6.2 and 1.7.2, here's a screenshot.

Is this still a concern in the latest Minecraft version 14w04b? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

I cannot confirm if this issue still persists in 14w04b. However, I have a world that seems to have the same issue in 1.7.4. I will have to upload this, which can take some time. I will keep you posted about the world download.

I have uploaded the world download here: Link removed (broken)
It's around 600 mb. I'm not entirely sure of the location where the spawn happened, but it shouldn't be more than around 500 blocks from spawn (give or take).

Same issue on 1.7.4 too, twice on the same server world

I have the same exact problem. I uploaded some of my pics about the problem for you all. Also, every time, minecraft crashes 2 min after playing. while it works, it just sits there

UPDATE: in minecraft, im stuck with 2 holes!!!!! at first, i had one but now 2!!!!! PLEASE FIX IT BEFORE MY WORLD COMPLETELY FALLS APART!!! You wouldn't believe how much work is on there!

I'm having this mass sheep spawning bug along with something like MC-2545 since I updated to 1.7.9 on my Mac running OSX Mavericks. It seems to happen regularly in a particular world, sometimes crashing the game and causing the world to be unplayable. I luckily have backups.