[MC-252683] Unexpected exception in the selector loop causing server lag

When I start a server, the server loads normally, but once a player joins the game, the server console begins spitting out

[Netty Epoll Server IO #1/WARN]: Unexpected exception in the selector loop.
io.netty.channel.unix.Errors$NativeIoException: epoll_wait(..) failed: Function not implemented

This causes the tps of the server to tank and makes the server unplayable as a result.

Tested the server on both java 17 and java 18, both openjdk binaries with the same results

Comments 14

user-f2760 2022-06-09T07:35:09Z

Is this specific to the world the server runs, or not?

I don't have this problem when joining a server.

Airplaneboy14 2022-06-09T07:53:28Z

It could be specific to the platform the server is hosted on rather than the world the server is running

user-f2760 2022-06-09T07:59:02Z

Ah, wait, duplicate of MC-252520, redownload the server software, that should fix the issue.

Elijah Watson 2022-06-10T00:37:30Z

@Dhranios just redownloaded the server jar from mojang's website and its still using netty 4.1.76 instead of netty 4.1.77

Jekkanadar 2022-06-10T01:12:03Z

@Dhranios

Agree with above from Elijah Watson, this seems to still be a problem and the newest server.jar still uses Netty Library 4.1.76.Final.

4 more comments

Oren 2022-06-14T15:22:30Z

This still seems to be an issue, despite this being closed. I am unsure how to verify whether the server software is running netty 4.1.77. but I'm seeing the issue when using the jar that I downloaded from here just a few minutes ago.

CaphalorAlb 2022-06-14T16:16:58Z

464232c6a505ecbc0e1df191129b4a4227df0b4aed0b221b49e0d479fd037679    io.netty:netty-buffer:4.1.76.Final    io/netty/netty-buffer/4.1.76.Final/netty-buffer-4.1.76.Final.jar
8b50a48b7860056d393aa335818c04c4b3784bd560e669c25a75feefe9e346dc    io.netty:netty-codec:4.1.76.Final    io/netty/netty-codec/4.1.76.Final/netty-codec-4.1.76.Final.jar
979831a58fde4ec3c6ddb7e0d1a60a6b086530b2d351ad4c2cff0cc7de2146c5    io.netty:netty-common:4.1.76.Final    io/netty/netty-common/4.1.76.Final/netty-common-4.1.76.Final.jar
bd0aff57e77d4bf43d3ee8e91c9dd8d5f852fb39775069e215cb485ba1654458    io.netty:netty-handler:4.1.76.Final    io/netty/netty-handler/4.1.76.Final/netty-handler-4.1.76.Final.jar
dae87e07d0a850eed419100eae846bb7ddbbc225e6214899b77cd8cf65f2e6a1    io.netty:netty-resolver:4.1.76.Final    io/netty/netty-resolver/4.1.76.Final/netty-resolver-4.1.76.Final.jar
9b63cbec7f9b0acf3f567fffbcf3bd3c4aca5eec0696ba00c6bf499ed3198c0c    io.netty:netty-transport:4.1.76.Final    io/netty/netty-transport/4.1.76.Final/netty-transport-4.1.76.Final.jar
a7a4fd01cc5d33ad54621d4a786563c555a6a65e6213330b2b024cb36df0bbc3    io.netty:netty-transport-classes-epoll:4.1.76.Final    io/netty/netty-transport-classes-epoll/4.1.76.Final/netty-transport-classes-epoll-4.1.76.Final.jar
30591493c990f5f2d4fb2140f1dfcfe59cca9ca63dd0322ff6439b719b7f81f3    io.netty:netty-transport-native-epoll:4.1.76.Final:linux-x86_64    io/netty/netty-transport-native-epoll/4.1.76.Final/netty-transport-native-epoll-4.1.76.Final-linux-x86_64.jar
736238f435b6cfe178c6a1f62e5d99b40b4b56c9308410219c3ba3aaf5bc8ce8    io.netty:netty-transport-native-epoll:4.1.76.Final:linux-aarch_64    io/netty/netty-transport-native-epoll/4.1.76.Final/netty-transport-native-epoll-4.1.76.Final-linux-aarch_64.jar
f507f645402d2e062c3542eff3c4b67e4e19e4d55e79724b31860a20ea271fbe    io.netty:netty-transport-native-unix-common:4.1.76.Final    io/netty/netty-transport-native-unix-common/4.1.76.Final/netty-transport-native-unix-common-4.1.76.Final.jar

this is still in the libraries.list if you download the current server jar

Oren 2022-06-14T16:23:53Z

@CaphalorAlb and @Dhranios, I have created this ticket which reflects this issue of netty being out of date.

ampolive 2022-06-15T11:06:15Z

@unknown This is fixed for a future version, not the current version.

Oren 2022-06-15T12:51:34Z

Thanks for the update. Is there a workaround in the meantime? Or when is the fix expected to release?

ampolive 2022-06-15T19:07:37Z

According to the 22w24a changelogs, this has been fixed in 22w24a.

mojang-bugs 2022-07-23T03:50:17Z

Can someone advise as to the expected release date of this fix?

This is a game breaking bug which has an easy fix. It should be back-ported to 1.19. It is well over a month, which is an unreasonable amount of time for a production build to be broken.

user-f2760 2022-07-23T04:55:11Z

No known release date yet, but 1.19.1 is (once again) in release candidates, so not long anymore.

Fixes are never backported, updates exist for a reason, just be patient.

MMK21 2022-07-23T10:51:24Z

Actually, there is an ETA: https://www.minecraft.net/en-us/article/minecraft-1-19-1-release-candidate-2

If no critical issues are found, we expect to release the full version next week.