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  1. Minecraft: Java Edition
  2. MC-202249

Angering passive mobs in new nether chunks very far away from previously generated chunks, then entering a nether portal causes server to completely freeze


    • Icon: Bug Bug
    • Resolution: Fixed
    • 1.17 Pre-release 1
    • 1.16.3, 1.16.4 Pre-release 1, 1.16.4 Pre-release 2, 1.16.4 Release Candidate 1, 1.16.4, 1.16.5, 21w17a
    • None
    • Community Consensus
    • Crash
    • Very Important

      Descovered a bug that goes far at least as 1.16, this is possibily also on 1.15 with Zombie Pigmen.
      I cannot seem to attach previous versions to the affected versions.

      Each test was done after deleting the region files in the nether to start cleanly.
      I created a datapack to spawn 40 piglins and give a bow/arrow, this is attached below.
      Memory allocation does not seem to matter, I tested this locally with Xms/Xmx 2G, while this still occurs on my main server with 5G set.
      The setup:
      1. Start a brand new server.
      2. Turn off Mob Spawning.
      3. Go to nether, go to the roof for simplicity.
      4. Teleport to 75,000 either X or Z (Minimum to effect is around 60K, 75K 100% garuntees a crash)
      5. Create a nether portal and go through it to generate the overworld chunks to verify it does not crash which it does not.
      6. Surround the portal with fencing or another way to prevent access, but have enough room to fire an arrow from.
      7. Summon Zombie Piglins outside of the fence contraption, 40 will 100% garuntee a crash in my testing
      8. Go into survival while standing in the fence contraption with the portal. anger the Zombie Piglins.
      9.Go through nether portal.
      Notice the Rx in F3 Debug screen slowly decreasing to 0 before freezing.

      Video attached, along with the 60s tick timeout watchdog crash – no other errors are created or shown... video is too large to attach So I have used an external source to link them.

      Edit: This causes the Watchdog to do it's job and terminate the hung java process, otherwise the server can hang indefinately if the watchdog is set to -1
      This is not a bug with the watchdog.

      Video from 1.16.2: https://streamable.com/fzb250
      Video testing on 1.16.4-pre1: https://streamable.com/e4ue8l

        1. 2020-10-16.png
          184 kB
        2. crash-2020-10-16_21.40.32-server.txt
          17 kB
        3. latest.log
          5 kB
        4. zpiglin.zip
          1 kB

            slicedlime [Mojang] slicedlime
            jakesta13 Jake Spencer
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