No support for dynamic worlds

[Wroud]

Currently threads created only once on WorldThreadingManager creation.
However fabric provides ServerWorldEvents.LOAD and ServerWorldEvents.UNLOAD events for level manadgement.

This will make this mod not work for any mods with dynamic level loading/unloading.

I've checked compatibility with my mod https://modrinth.com/mod/mc-worlds and it doesn't work in such setup

1. first add Wrolds
2. create new world and then create any world using Worlds
3. teleport to this created world
4. exit game
5. add worldthreader
6. load wolrd

this will make server crash:

   [02:22:57] [Server Watchdog/ERROR] (Minecraft) A single server tick took 60.00 seconds (should be max 0.05)
[02:22:57] [Server Watchdog/ERROR] (Minecraft) Considering it to be crashed, server will forcibly shutdown.
> :[02:22:58] [Server Watchdog/ERROR] (worldthreader) Thread Thread[#90,Server Watchdog,8,main] is requesting exclusive world access. However, only world threads may request exclusive access during the world ticking!

[2No2Name]

I wasn't aware this is a thing, thanks for the detailed report. This can probably be fixed relatively easily

[2No2Name]

The above commit should help with compatibility, but currently it will throw an exception when you modify the worlds/levels during the world/level tick. If you don't already, I suggest you make sure your commands only execute between the ticks, e.g. by sending the command to the minecraft server executor

[2No2Name]

If you confirm this works for you, I will make a new release

[Wroud]

thanks, this should work, i will check it today, currently in vanilla implementation there also will be an exception if world added during tick so i use getServer().execute but there also some fabric hooks that can be used on my side to ensure level added between ticks

[Wroud]

hmm, it now behave differently.
Added world added and processed in it's thread:
[23:31:45] [worldthreader_minecraft:test/INFO] (mc-worlds) Preparing spawn: minecraft:test

but server freezes here

probably after execution this code in mc-worlds

    processingChunk = chunkSource.addTicketAndLoadWithRadius(
        TicketType.PLAYER_SPAWN, chunkPos, 0)
        .whenComplete((result, throwable) -> {
          if (throwable == null) {
            BlockPos blockPos2 = PlayerSpawnFinder.getSpawnPosInChunk(serverLevel, chunkPos);
            if (blockPos2 != null) {
              serverLevelData.setSpawn(RespawnData.of(serverLevel.dimension(), blockPos2, 0.0F, 0.0F));
              spawnChunksToCheck.clear();
            }
          } else {
            McWorldMod.LOGGER.error("Failed to load spawn chunk at {}: {}", chunkPos, throwable.getMessage());
          }
        });

so world ticked once and then freezes

[Wroud]

hmm actually without addTicketAndLoadWithRadius world also freezes and ticked only once

it stuck on the WorldThreaderTickPhase.WORLD_TICK

probably this is because in my implementation i have some phases before invoking level.tick() and i see that you have some mixins relay on it

basically mc-world will not call level.tick() before level prepared for ticking and will use this ticks for level initialization

[2No2Name]

Maybe the other threads are frozen/paused at a more relevant place in the code. The barrier enforces that all threads continue only if all threads have arrived in the barrier. If you don't find a solution, I will try loading your mod in my development environment and see

[2No2Name]

basically mc-world will not call level.tick() before level prepared for ticking and will use this ticks for level initialization

I don't quite understand what it means to prepare the level for ticking or initialize the level, I assumed you would just add a level or remove a level from the levels collection of the minecraft server between the gameticks

[Wroud]

i've tested with default tick and got this:

Description: Exception ticking world

java.lang.ClassCastException: class dev.wroud.mc.worlds.manager.level.data.WorldsLevelData cannot be cast to class no2.worldthreader.common.mixin_support.interfaces.PrimaryLevelDataExtended (dev.wroud.mc.worlds.manager.level.data.WorldsLevelData and no2.worldthreader.common.mixin_support.interfaces.PrimaryLevelDataExtended are in unnamed module of loader 'knot' @1d76aeea)
        at knot//net.minecraft.server.level.ServerLevel.redirect$zln000$worldthreader$getScheduledEventsUnsafe(ServerLevel.java:2981)
        at knot//net.minecraft.server.level.ServerLevel.tickTime(ServerLevel.java:452)
        at knot//net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:344)
        at knot//dev.wroud.mc.worlds.server.level.CustomServerLevel.superTick(CustomServerLevel.java:70)
        at knot//dev.wroud.mc.worlds.server.level.CustomServerLevel.tick(CustomServerLevel.java:66)
        at knot//no2.worldthreader.common.ServerWorldTicking.tickThreaded(ServerWorldTicking.java:67)
        at knot//no2.worldthreader.common.ServerWorldTicking.runWorldThread(ServerWorldTicking.java:36)
        at knot//no2.worldthreader.common.thread.WorldThreadingManager.lambda$new$0(WorldThreadingManager.java:66)
        at java.base/java.lang.Thread.run(Unknown Source)

this seems because for custom dimensions i use different level data implementation

[Wroud]

I don't quite understand what it means to prepare the level for ticking or initialize the level, I assumed you would just add a level or remove a level from the levels collection of the minecraft server between the gameticks

in mc-worlds i'm trying to be as close as possible to vanilla behaviour and in vanilla dimensions initialized in a few phases:

1. level created and added to the levels map
2. if level not initialized previously it will be initialized (initial spawn + bonus chest)
3. forceDifficulty
4. prepareLevels (tickets activation)

only after all this phases levels will start ticking

but i think that i can execute original level.tick every time even during level initialization, but i need to test if there is no problems with it

logic is like this:

                          -> yes -> call original level tick
tick -> is level prepared -
                          -> no  -> call preparation logic tick

[2No2Name]

1. Worldthreader assumes: The minecraft server ticks all levels together (vanilla: after each other, worldthreader: parallel).
   1. This would require either not ticking any level until the new level has gone through steps 2-4 or only adding the level after steps 2-4 are done. Is it possible for you to only add the level to the minecraft server's levels map when it is ready to tick, or does this lead to other issues?
2. I would like to understand what the purpose of your custom level data implementation is. But I already see that worldthreader is assuming that a level is the "main" overworld level (which does some exclusive stuff, like the functions) based on the level data type, and not based on the "tickTime" property. Changing that probably helps already