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  1. Minecraft: Java Edition
  2. MC-137300

ConcurrentModificationException thrown when upgrading world

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    • Confirmed

      The bug

      Converted worlds produce the error below in constantly when flying around, and chunks that should get loaded are not being loaded as seen in the screenshot.
      The example log took me ~30 seconds to get a few erors.

      [16:38:58] [Server thread/FATAL]: Error executing task
      java.util.concurrent.ExecutionException: java.util.ConcurrentModificationException
      	at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_181]
      	at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_181]
      	at k.a(SourceFile:200) [1.13.2-pre1.jar:?]
      	at net.minecraft.server.MinecraftServer.b(SourceFile:726) [1.13.2-pre1.jar:?]
      	at net.minecraft.server.MinecraftServer.a(SourceFile:681) [1.13.2-pre1.jar:?]
      	at dgh.a(SourceFile:131) [1.13.2-pre1.jar:?]
      	at net.minecraft.server.MinecraftServer.run(SourceFile:584) [1.13.2-pre1.jar:?]
      	at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]
      Caused by: java.util.ConcurrentModificationException
      	at java.util.HashMap$HashIterator.nextNode(Unknown Source) ~[?:1.8.0_181]
      	at java.util.HashMap$EntryIterator.next(Unknown Source) ~[?:1.8.0_181]
      	at java.util.HashMap$EntryIterator.next(Unknown Source) ~[?:1.8.0_181]
      	at bnj.E(SourceFile:1162) ~[1.13.2-pre1.jar:?]
      	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_181]
      	at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_181]
      	at k.a(SourceFile:199) ~[1.13.2-pre1.jar:?]
      	... 5 more
      

      Code analysis

      Code analysis by md_5 can be found in this comment.

        1. 2018-10-16_18.26.23.png
          2.73 MB
          Tobias Hotz
        2. 2018-10-16-1.log
          16 kB
          Tobias Hotz

            fry [Mojang] Georgii Gavrichev
            ichttt Tobias Hotz
            Votes:
            14 Vote for this issue
            Watchers:
            6 Start watching this issue

              Created:
              Updated:
              Resolved:
              CHK: