[MC-104897] End crystals placed on exit portals generated before 1.9 do not respawn the ender dragon

The bug

The ender dragon cannot be respawned at an end portal if the dragon was killed before 1.9 and the resulting end portal is generated at a location other than (0,<y>,0).

Furthermore, when placing the necessary end crystals on the portal, this error will be logged:

[Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_51]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_51]
	at k.a(SourceFile:200) [1.13.1.jar:?]
	at net.minecraft.server.MinecraftServer.b(SourceFile:726) [1.13.1.jar:?]
	at net.minecraft.server.MinecraftServer.a(SourceFile:681) [1.13.1.jar:?]
	at dgg.a(SourceFile:131) [1.13.1.jar:?]
	at net.minecraft.server.MinecraftServer.run(SourceFile:584) [1.13.1.jar:?]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_51]
Caused by: java.lang.NullPointerException
	at bog.e(SourceFile:531) ~[1.13.1.jar:?]
	at asj.a(SourceFile:52) ~[1.13.1.jar:?]
	at atd.a(SourceFile:187) ~[1.13.1.jar:?]
	at tg.a(SourceFile:326) ~[1.13.1.jar:?]
	at uc.a(SourceFile:925) ~[1.13.1.jar:?]
	at nr.a(SourceFile:53) ~[1.13.1.jar:?]
	at nr.a(SourceFile:11) ~[1.13.1.jar:?]
	at ix.a(SourceFile:10) ~[1.13.1.jar:?]
	at ix$$Lambda$2000/1475818869.run(Unknown Source) ~[?:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_51]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_51]
	at k.a(SourceFile:199) ~[1.13.1.jar:?]
	... 5 more

What I expected to happen was:

The ender dragon would respawn.

What actually happened was:

The ender dragon did not respawn.

How to reproduce

Download the attached world

[media]

Load the world in 1.10.1 or later.
Enter the active end portal. (You should spawn at a stronghold)
Locate the exit portal, and place the necessary crystals.
→ ❌ See that the respawning process does not restart.

Code analysis (from MC-105304)

What seems to be happening (using MCP names) is that the fix for MC-103497 made DragonFightManager.respawnDragon() always try to use exitPortalLocation, even though findExitPortal() only sets this field when the detected portal is at (0,0). It should instead use the value returned by findExitPortal(), properly offset of course.

Workaround can be found here.

Linked issues

blocks 1

MC-112774 Legacy end portal is replaced at the beginning of respawning instead of at the end Resolved

is duplicated by 11

MC-105157 Dragon Does not respawn when End crystals are placed Resolved

MC-105304 Dragon cannot be respawned in an old world Resolved

MC-106243 Cannot respawn Ender Dragon in old World Resolved

MC-107325 Ender Dragon Will Not Respawn Resolved

MC-109104 Portal in the end is at Y=64. Placing 4 crystals does not respawn the dragon Resolved

6 more links

relates to 1

MC-104736 DragonFight data is not completely restored after corruption from MC-103497 Resolved

Attachments

bug_dragon.txt

MC-104897.zip

world_MC-104897.zip

Comments 34

[Mod] Neko 2016-07-02T02:03:21Z

Old portals from 1.8 and below are generated where the dragon dies; new portals are generated at 0, 0 in 1.10. Make sure you are trying to respawn the dragon at the new portal.

pokechu22 2016-07-02T02:07:27Z

I'm 99% sure (might be wrong) that if the dragon hasn't been respawned once, then you still need to do it at the old portal since there is no new portal. And since the old portal still has portal blocks in it, it seems like the dragon hasn't been respawned.

Patrick 2016-07-02T15:15:02Z

There is no portal at coordinates 0,0

Patrick 2016-07-02T15:15:36Z

Coordinates 0,0

[Mod] redstonehelper 2016-07-02T18:40:34Z

Place the end crystals in the middle of the 3 wide bedrock sections. If that doesn't work, please attach the affected world. In which versions has this world been opened? Any 1.10 snapshots? 1.10?

24 more comments

Patrick 2016-07-02T20:20:37Z

1.7 was the last time I visited The End, I had visited all other realms up to 1.10 first since I had no reason to visit The End until 1.10.
What am I supposed to attach?

null 2016-07-02T21:45:34Z

Please attach the world file (minecraft/worlds/WORLDNAME) by compressing it and attaching the zip file.

Patrick 2016-07-03T14:38:20Z

Are you talking about the saved game file on singleplayer? If so, it's nearly a Gigabyte in size.

pokechu22 2016-07-03T16:41:12Z

Yea, that's what we're referring to. If it's 1 gigabyte, probably it's best to not upload the overworld and nether areas (since those are likely to be the largest), so maybe just put the files and folders data, DIM1, and level.dat all into a zip folder and upload that.

null 2016-07-03T18:47:23Z

The way you placed the ender crystals in the first screenshot is incorrect. See @unknown's comment.

[Mod] Neko 2016-07-03T19:10:28Z

@unknown ~~This method works just fine. (See third screenshot~~) Nevermind, it doesn't work on old portals.

[Mod] Neko 2016-07-03T19:19:25Z

Can confirm, end crystals do not work on old portals.

[Mod] Neko 2016-07-03T20:01:27Z

Until this bug is fixed, here's a method to generate a new end portal.

Patrick 2016-07-03T22:48:25Z

Here's the requested files.

marcono1234 2016-08-04T13:59:01Z

@unknown could you please add a moderator or helper note (just some kind of panel) to the description linking to your workaround

user-f2760 2016-08-04T14:01:27Z

No need for a panel.

marcono1234 2016-08-04T14:40:32Z

At least a link then that players who suffer from this can "fix" it themselves?

Dídac García 2016-09-09T21:11:42Z

I have a vanilla server and I have the same problem. My world was generated in 1.3 version more or less. I put the crystals in the correct place and dragon are not respawning.

Dídac García 2016-09-09T21:12:16Z

The log of my Vanilla server

marcono1234 2016-09-12T12:53:13Z

Use this workaround and please @unknown link to this work around.

marcono1234 2016-09-12T13:11:30Z

Thank you 🙂

user-f2760 2016-09-12T13:14:48Z

Turns out we're both blind, it was already linked above the code analysis, removed that one, is it wasn't as spotable.

Socks 2017-05-15T02:48:53Z

confirmed for 1.11.2 - happened on Realms server. OP had to apply fix to spawn the dragon

carpet0928 2018-10-16T21:59:30Z

I'm currently having trouble reproducing this for 1.13.2-pre1 because the test world I've attached gets corrupted by MC-137300 upon loading.

RimaNari 2018-10-17T15:11:00Z

I was able to workaround MC-137300 by loading the world in 1.13.1 first and then loading it in 1.13.2-pre1. This should not interfere with reproducing this bug.

I can confirm for 1.13.2-pre1.

carpet0928 2018-10-17T18:44:26Z

Thank you @unknown! That's useful to know. I've added 1.13.2-pre1 to the affected versions list now.

carpet0928 2018-11-07T20:24:37Z

When I enter my test world in 18w45a, a new exit portal is generated at (0,0) (the original portal is kept), and the ender dragon respawns. Is this due to a newly introduced bug that I'm not aware of?

RimaNari 2018-11-10T19:23:20Z

I cannot confirm what you are saying @carpet0928 .

When I load in 14w45a and enter the end, the exit portal is at its usual position slightly offset from 0,0 and there is no ender dragon. I cannot respawn the dragon by the expected process, but once I break a bedrock block from the exit portal and place a single end crystal on it, it triggers the creation of another exit portal at 0,0. Then I can respawn the dragn on the new portal at 0,0.

So it's the same as it always was for me, and the bug persists... not sure what you did?

carpet0928 2018-11-10T21:05:51Z

I'd say that my last comment was self-explanatory and helped explain what I did fairly well, but, strangely enough, I'm now able to reproduce my own report again as well. This isn't the first time something like this has happened to me, and I'm not the smartest person so I'm not 100% sure why things like this happen to me sometimes.

You've done a great job helping me keep this ticket up to date. I appreciate that very much 🙂

RimaNari 2018-11-10T22:27:37Z

I assume you forgot a negation in your comment, actually meaning that you are not able to reproduce your own report. You wrote that you were able to reproduce again, but apparently that's a typo.

I can imagine that maybe you didn't use a fresh copy of the test world, but one that was opened already. If one has several copies of a world in the saves folder, maybe one original and one that was opened in another snapshot already, it certainly gets confusing quickly. It doesn't help that Minecraft displays the world's name (which is the same for two copies of a world) as the bold-faced largest piece of text of a save, and the folder name only smaller and less prominent. So that would be one possible explanation.

Anyways, glad that I could help 🙂

carpet0928 2018-11-10T23:43:12Z

Nope, no mistakes here, it's true that I can reproduce now.

RimaNari 2018-11-11T11:52:29Z

Ah, sorry - you are able to reproduce the bug, but you are not able to reproduce what you observed in your comment three days ago. That's what you meant, okay. Everything fine 🙂

- 2020-05-05T04:25:18Z

Hey is anyone working on fixing this? I know its like old and an edge case to the max, but i have a world that me and my son started in 2008 or 2009. We killed the dragon back then. Fast forward to this year, my youngest son is old enough for minecraft now (6) and we tried to go kill the ender dragon again. Everytime we try and spawn it we get a null pointer exception FATAL error as above.

I am in favour of the person who "fixed" the other bug that caused this bug being made to fix this one. 🙂

EDIT: just saw that there is a work around! thanks for that! ( https://imgur.com/a/pa3zO ) i am leaving this post as proof that this bug is still biting people out there like me!

the work around is to go to creative, destroy the portal, and then place an end crystal on a piece of obsidian that you randomly place anywhere. then the portal will spawn again.

can you not close it as "work around" status? and list that? because it says unsolved in the status.

László Rasmussen 2021-02-22T12:05:09Z

I can confirm for 1.16.5