Inevitable client freeze and then time out?

[Leiffality]

Hello, I'm not sure how to troubleshoot this problem. I'm running a modded server with 208 mods on forge 1.12.2 - 14.23.4.2730.

So far I've managed to fix most of the issues myself as I have some inside knowledge of how Java code works. Crash reports, logs, debug logs, etc.

Well, there's one problem that continues to plague the server and all who connect to it (upwards of 10 people).

Eventually, inevitably, the client will freeze for seemingly no reason and then time out. It may take anywhere from a minute to hours for Minecraft to respond again, but once it does joining the server again is quick and easy.

It's likely that this is the reason those with low-end PCs can't join without getting timed out from the get-go as well.

 

So, I opened f3 pie debug and ran around until my game froze... nothing, not even a blip on the pie chart. RAM was only at like 80%(of 5GB) usage and garbage collection was smooth up to that point as well due to some JVM args we all use.

In case it matters, here are those args:

 

Spoiler

-d64 -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -XX:MaxGCPauseMillis=80 -XX:+UseStringDeduplication -XX:+UseCompressedOops -XX:+UseCodeCacheFlushing -XX:ParallelGCThreads=4

At first I thought it might be Dynamic Surroundings crashing the sound system around 6-20 times in a couple seconds every so often but this happens to the players that removed that mod as well.

How would I go about troubleshooting the cause? I can't exactly merge sort the entirety of the server effectively and if it's a client issue then why does it only happen on the server and never in singleplayer?

Any suggestion is welcome. Do I look at logs? If so, which ones? Where is the information that tells me what is freezing up the game?

[_Cruelar_]

Look at the game logs of the player that freezed and also at the Server logs.

You can provide these to get more help.(Use pastebin or Github for larger files)

[Leiffality]

Update! 

The main offenders seem to be dynamic surroundings and better advancements. Whenever the time out happened the console would spit out "Loaded 790 advancements". With a bit of guess work I tested the game with better advancements removed and lo and behold the time outs stopped. I'm still testing to see if they're still happening though. 

 

They are, though not nearly as frequently so it'll probably be a while before I can find anything.

Edited August 3, 2018 by Leiffality