[MC-297651] Crash when running a server for too long

Affects 1.21.5-pre-3, 1.21.8

When running a server for too long, the game crashes with an ArrayIndexOutOfBounds error. This happens because MinecraftServer.ticks (yarn, linkie won’t find it in MojMaps for some reason) overflows, then the array that keeps track of tick times is accessed with index ticks % 100, which is -48.

To reproduce:

Start a server, preferably a void world with all the performance gains you can find (eg random tick speed at 0)
Run /tick sprint 10000000d or some other large number
Wait

int j = this.ticks % 100;
this.recentTickTimesNanos -= this.tickTimes[j];

Environment

Ubuntu dedicated server (should work in singleplayer too)

Attachments

crash-2025-03-21_17.40.23-server.txt

Comments 8

skycatminepokie 2025-03-18T20:54:13Z

I’ve been informed that ticks in yarn is tickCount in MojMap

[MOD] Greymagic27 2025-03-19T18:04:16Z

I had a server set on this tick sprint with the maximum tick rate as well, but had no crash.

Are you able to attach the crash report please?

skycatminepokie 2025-03-21T15:55:58Z

Waiting for mine to crash on 1.21.5-rc1. I’ll post the crash report once it does.

skycatminepokie 2025-03-21T15:56:58Z

Estimated time: instant according to tick query lol

skycatminepokie 2025-03-21T16:00:20Z

Oh geez I did the math it’ll be about 3 years before it crashes at 1 million tps. I suppose this’ll be closed as invalid or won’t fix then, I’ll make a mod to fix it for my use case.

skycatminepokie 2025-03-21T16:04:24Z

Update: I missed a factor of 60, see you in three days

skycatminepokie 2025-03-21T16:14:31Z

Update: The tick speed limit is bypassed by tick warp, so it’ll be sometime today

skycatminepokie 2025-03-21T18:20:59Z

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 2025-03-21 17:40:23
Description: Exception in server tick loop

java.lang.ArrayIndexOutOfBoundsException: Index -48 out of bounds for length 100
	at net.minecraft.server.MinecraftServer.a(SourceFile:962)
	at net.minecraft.server.MinecraftServer.y(SourceFile:706)
	at net.minecraft.server.MinecraftServer.a(SourceFile:290)
	at java.base/java.lang.Thread.run(Thread.java:1583)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
	Minecraft Version: 1.21.5 Release Candidate 1
	Minecraft Version ID: 1.21.5-rc1
	Operating System: Linux (aarch64) version 5.15.0-1068-oracle
	Java Version: 21.0.6, Ubuntu
	Java VM Version: OpenJDK 64-Bit Server VM (mixed mode, sharing), Ubuntu
	Memory: 148808024 bytes (141 MiB) / 695205888 bytes (663 MiB) up to 2147483648 bytes (2048 MiB)
	CPUs: 4
	Processor Vendor: ARM
	Processor Name: Neoverse-N1
	Identifier: ARM Family 8 Model 0xd0c Stepping r3p1
	Microarchitecture: unknown
	Frequency (GHz): -0.00
	Number of physical packages: 1
	Number of physical CPUs: 4
	Number of logical CPUs: 4
	Graphics card #0 name: Virtio GPU
	Graphics card #0 vendor: Red Hat, Inc.
	Graphics card #0 VRAM (MiB): 0.00
	Graphics card #0 deviceId: unknown
	Graphics card #0 versionInfo: version: 01
	Virtual memory max (MiB): 11994.52
	Virtual memory used (MiB): 5226.93
	Swap memory total (MiB): 0.00
	Swap memory used (MiB): 0.00
	Space in storage for jna.tmpdir (MiB): <path not set>
	Space in storage for org.lwjgl.system.SharedLibraryExtractPath (MiB): <path not set>
	Space in storage for io.netty.native.workdir (MiB): <path not set>
	Space in storage for java.io.tmpdir (MiB): available: 33113.47, total: 46041.01
	Space in storage for workdir (MiB): available: 33113.47, total: 46041.01
	JVM Flags: 1 total; -Xmx2048M
	Server Running: true
	Player Count: 0 / 20; []
	Active Data Packs: vanilla
	Available Data Packs: minecart_improvements, redstone_experiments, trade_rebalance, vanilla
	Enabled Feature Flags: minecraft:vanilla
	World Generation: Stable
	World Seed: 8466797366112192443
	Suppressed Exceptions: ~~NONE~~
	Is Modded: Probably not. Server jar signature and brand is untouched
	Type: Dedicated Server (map_server.txt)

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