Large Chunk Detected - problem?

Discussion in 'Spigot Help' started by takatalvi, Mar 7, 2019.

  1. Hi,

    I recently started getting a message for specific locations in the world (2 specific locations) - the console tells me that a large chunk has been detected and it gives me the number of the .mca region file. This occurs for 2 files, which I can see are really large. They are nearing 18MB, while all the other files are under 10MB. I see the cause, the players living there simply went all-in and build a LOT of intricate stuff. The server works fine, as always. That's why I'd like to ask - is this a problem? Or an indication of a future problem? I don't see the size growing considerably, the files grew in size naturally. But still, is there a limitation on region files that could threaten these files or the server?

  2. Are you using PaperSpigot? This sounds like the problem related to the chunk dupe glitch, paper will warn you about this when it happens.
    • Agree Agree x 1
    • Winner Winner x 1
  3. I'm not using PaperSpigot, just normal Spigot. The chunks are all in order, at least in-game, so if there is a glitch, it's most likely in the back-end somehow. The size of those files is just out of the ordinary. In any case, warning is one thing, possible difficulties are another. Would PaperSpigot be able to somehow resolve this? Is PaperSpigot available for the latest 1.13.2 version? Any info is appreciated :)
  4. is this the message you are getting?
    "Large Chunk Detected: ({0}, {1}) Size: {2} {3}", new Object[]{i, j, k1, this.b})"
  5. No.
    • Agree Agree x 1
  6. The only way to resolve it, is to stop players from making too large of chunks.
    Chunks are permitted to a size of (I'm not 100% certain on this) 1Mb.
    The latest book dupe was something that over did the size of a chunk, which in turn stopped chunks from saving, and players could dude items.

    This was recently fixed in Spigot, which is why you are getting those messages in your console
  7. The message is most likely the same, in the log it looks like this:
    Code (Text):
    [12:09:32 WARN]: Large Chunk Detected: (5, 15) Size: 1,475 ./world/region/r.-10.15.mca
    Ok, the way I understand it is, there are chunks over 1MB (or similar size) and Spigot gives me a warning about these chunks. I will definitely check them out individually, I had the idea that it could have been caused by a lot of items in chests that have a lot of NBT data. When you mentioned the item duplication glitch, this one player that has one of these chunks has a history of exploiting it, a long time ago. Interesting.
  8. This is why I just perm ban players who join the game to not play minecraft, but to be malicious. They're wasting your time.
    • Agree Agree x 2
  9. SpacePuppeh


    Totally agree. People wanting to exploit the game are just a continual annoyance.
    I thought they introduced something meant to fix it recently? You might want to check their builds, but I don't want to go into it on Spigot lol.
  10. Look in the player's chests. I bet you find a 50 page book filled with Chinese characters.
    • Winner Winner x 1
  11. This one was the closest thing - I searched and searched, and after my 3rd attempt I found a chest in the floor, just above bedrock (his base goes all the way down). When I tried to open the chest, my game crashed. So I made a schematic out of it and exported it for further investigation (the schematic only has the chest in it and it's 5MB, wtf). When I destroyed it, a few shulker boxes fell out with a delay. Those shulker boxes are filled with books, and placing one will result in a client crash, not mentioning opening one. So I isolated the problem, will investigate the schematic outside the server, and this guy is in big trouble. There is one more region with a problem like this, I'm still about to find it, wish me luck. And thanks for the suggestions, guys!

    The lesson learned - there is probably no real limitation on the size of .mca files, it just depends on what your server and/or client can handle.

    EDIT: Seriously guys? A 50-page book filled with Chinese characters? Is that a known exploit? Because that's exactly what I found - I opened the data using NBTExplorer and there it is. Jeez, now the fun begins.
    #11 takatalvi, Mar 8, 2019
    Last edited: Mar 8, 2019
  12. I'm not 100% sure if it's an exploit. It's probably just behaviour that the server / client wasn't prepared for. If you call it an exploit, I would expect it to be patched, but how does one patch something like this? It's not like you can prevent a player from having more than x books in their chest. You also can't prevent a player from dumping in Chinese characters...

    You could potentially make a plugin that would prevent this if it's not taken care of by Spigot. I'm personally not dealing with these kind of exploits for my own server, so I'm interested to see this can be prevented.
  13. Its actually huge exploit. Long story short
    Book with chinese type characters, too many of those books, compression when saving chunk exceeds chunk save limit, chunk doesn't save, player dupes items.
    md_5 fixed this by allowing larger chunk saves, which would in turn send a message to console each time this happens.
    Aikar also fixed this in Paper 2 different ways. 1) I think you can stop the production of these books (dont quote me on that one) 2) when these chunks try to save, it saves the data to another file and also warns the console of these locations.
    • Like Like x 1
  14. Yes, and it's been around since last November! I'm using this plugin to somewhat block it. But I'd like to find a better one - This plugin doesn't remove books already in the world and I've heard there are similar exploits with name tags.
  15. MiniDigger


    wrong. paper actually has a different way of dealing with uber sized chunks. instead of creating a giant region file it will "overflow" in a new file.

    the result is still the same tho. you need to investigate, ban the player if needed and then clean up the mess they created.
    • Like Like x 1
  16. Thanks for that, I'll definitely check out BookDuplicationFix, although they only mention 1.12 support, not 1.13. Getting a notification when someone tries some black magic for kids sounds really nice, these people often have no idea what they can cause, they simply don't think about consequences..

    Update from a technical point of view:
    I removed the problematic containers, I believe I wiped them off completely. However, that didn't reduce the size of the .mca file, I guess that's because of how they are designed, who knows.. The chunk is not "oversized" anymore, though. Funny thing is that when I took the shulker box with the books to another, far-away plain location, and tried placing it there, the size of this far-away region's .mca file went up about 7MB and I can't seem to get rid of the increase. But I don't consider it an issue for now, a few MBs is nothing to worry about, the important thing is that those books are gone and the specific chunk is all right now.

    Update from a social point of view:
    I talked to the guy, explaining that he simply cannot do that he will not be part of the server anymore. I chose this way, as he actually showed interest in making the server better and how he appreciates that this kind of server exist. Kind of ironic, that a player who "appreciates the community" would try this kind of thing. He made an excuse that he wanted to do an experiment with something like a "ban book", which he first tried in a vanilla SP game but later tried it online. Then he got to the point where opening the chest would disconnect him and couldn't do anything about that anymore. I made sure he understands that unless he reports such problems, he will be banned.
  17. Some players just want to experiment (let's use WorldEdit to place 2 million floating fences), don't really think about what can happen, and end up causing problems that they can't fix. I'll warn them not to abuse WorldEdit, and if they do it again, I simply take away their WE permissions.

    Other players (anyone from Germany playing 1.8.8 on a Creative server) come on to try known exploits just to cause problems.

    Only once was a player able to do something I wasn't able to fix and had to restore one .mca file from backup.

    I have one player who is pretty smart, likes to build things, and reports any problems he finds to me so I can take care of it. He tried and reported the chunk save / duplication problem to me. I'd make him a moderator, but we really don't need one and I don't want to encourage him to spend extra time on the server instead of doing school work.
    • Agree Agree x 1
  18. Experiments can be fun, but you need to take other people's work into considerations. If you don't, you can cause problems, and that's both a nuisance, and a way to find and fix holes in the server's setup.

    I especially agree with the last paragraph, I have no moderators either, but the fact that there are some seriously responsible kids (age really doesn't matter here) gives me hope that the whole playerbase is not retarded :)
  19. My point is that just switching to paper doesn't resolve the large chunk issue. Just because paper has a different approach, doesn't mean his large chunk goes away.