Luke100000 / MultiServer

An approach to run and manage multiple servers in one Java instance for increased memory efficiency.

MultiServer

MultiServer allows you to run multiple servers in a single Java instancing, saving RAM and allows for direct access to starting and stopping servers. It also allows to reuse a single template world, eliminating chunk generation costs completely.

Instances run mostly independent and their view and simulation distance, thread count and world size can be configured individually.

Setup

Create a mods dir and provide MultiServer, the fabric API, and FabricProxy-Lite.

Optionally install mods from the compatible performance mods section.

Download the fabric server and start it once, with mods, to prepare the lobby server and config.

Download velocity and setup modern forwarding.

player-info-forwarding-mode = "modern"

Define the server spots using the syntax port_{PORT}. Make sure they match with the range specified in the MultiServer.json config:

lobby = "127.0.0.1:25000"
port_25001 = "127.0.0.1:25001"
port_25002 = "127.0.0.1:25002"
port_25003 = "127.0.0.1:25003"
port_25004 = "127.0.0.1:25004"

Set up the fabric proxy in config/FabricProxy-Lite.toml and provide the secret as saved in forwarding.secret.

Disable online mode in server.properties. It will be handled by velocity.

java -Xms256M -Xmx256M -XX:+UseG1GC -XX:G1HeapRegionSize=4M -XX:+UnlockExperimentalVMOptions -XX:+ParallelRefProcEnabled -XX:+AlwaysPreTouch -jar velocity.jar &
java -Xmx6G -Xms6G -XX:+UseG1GC -Dsun.rmi.dgc.server.gcInterval=2147483646 -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M -jar fabric_launcher.jar nogui

Compatible Performance Mods

Following mods appear to be compatible:

• Krypton
• LazyDFU
• Lithium
• MemoryLeakFix
• ServerCore
• StarLight
• FerriteCore
• Alternate Current
• ModernFix

Optimizations

MultiServer disables spawn chunks generation and manages the render and simulation distance dynamically, but you may want to adapt following settings in the properties file.

• entity-broadcast-range-percentage=75 Description Affects mostly networking usage.

Terra

MultiServer has a limited world size to make extensive use of the deduplication techniques of the approach. To make sure the world still contains enough to explore, we used terra to spice up the world gen and shrink the biome size just a little:

Follow https://terra.polydev.org/install/mod-server-world-creation.html to set up terra, clone the default pack and in meta.yml adapt global-scale to a smaller value, we used 0.75.