When moving players from one server to another Luckperms appears to be opening threads which are then not closed or not closed within a long time at least.

My test has been the following:

1. Open all servers and let players join the hub server.
2. Let players join the queue to the main server which starts sending them over as it is currently empty.
3. Using watch -n1 "ps huH p <pid of waterfall server> | wc -l" I can see the number of threads increase dramatically from the normal level of around 150 to several thousands.
4. With a very large amount of players it sometimes goes up to around 10 000 threads at which point the operating system will no longer allow any more threads to be opened and all applications crash.

When Luckperms is removed this no longer happens and the thread count stays at a normal level of about 100-200 threads at a time.

There is no such issue with the Bukkit versions.

The server is running Waterfall 282 and LuckPerms-bungee 4.4.17

Can you generate a java thread dump please. :)

I did that and it pointed to another plugin, sorry about blaming you guys. As the error didn't happen without luckperms it appeared to be the issue at first but it appears I was mistaken. The other plugin has been updated and it has solved the issue.

Thanks for giving me the tool to solve it though!

Oh and it wasn't even just one plugin, apparently Plan has the same issue too.