Very Many Players (Fabric) — a mod for improving performance of servers with a large number of players online in Minecraft

Very Many Players (Fabric) — a mod for improving performance of servers with a large number of players online in Minecraft

Very Many Players is a Fabric mod that improves Minecraft server performance when a lot of players are online at the same time. The author has gathered a series of targeted optimizations to vanilla code under one project: faster entity search within a radius, asynchronous chunk loading on login, and other things that administrators of large servers usually have to coordinate among themselves. The behavior of the game doesn't change in the process — the mod doesn't alter any mechanics, it only speeds up service-level processes.

What the mod does on the server

The foundation is rewritten "hot" spots of server code. Instead of iterating over all entities in the world to find the nearest ones, the mod keeps spatial indexes and performs the selection quickly and predictably. The same principle underlies searching for players within a radius for packet sending, trackers, and natural spawn checks. On a small server the difference is unnoticeable. With 100+ players scattered across the map, every tick of such checks becomes expensive — and that's exactly where the mod's work becomes noticeable.

Chunk and network handling

A custom chunk-sending system is the second major part of the mod. Chunks are queued by priority (closer to the player — sooner) and can be sent with a rate limit. This is especially noticeable when new players connect: instead of immediately "firing off" a hundred chunks at once and flooding the network, the server sends them in an even stream.

A separate feature is per-player view distance at the network packet level. Each player can receive their own number of chunks around them without changing the server's overall setting.

Bot protection

Network connection-processing loops are split into groups: the handshake and login stages are handled separately from the in-game state. If a wave of bots tries to mass-join the server, it only loads its own loop, while already-connected players don't experience delays.

Config

The file is config/vmp.properties. It's created automatically after the server first starts with the mod. The format is standard Java .properties, editable with any text editor. Changes are picked up on server restart.

Parameters

Conclusion

Very Many Players keeps TPS stable on servers with dozens to hundreds of concurrent players, without changing game mechanics. The gain comes from the sum of small optimizations — faster entity search, offloading heavy operations from the main tick, streamed chunk sending.  VMP is most useful on projects with a constantly high player count: SMP with 50+ slots, minigame servers, public anarchy servers.