MultiPaper

MultiPaper is in public beta. Most features work for most players most of the time, however things can occasionally break.

1.18 Paper fork that enables a server admin to scale a single world across multiple servers. Multiple MultiPaper servers run the same world and use a MultiPaper-Master to coordinate with eachother and store server data. While the MultiPaper-Master is usually run as a standalone server, it can also be run as a BungeeCord plugin, which has some benefits including being able to send players to the least busiest server when they join.

MultiPaper 2.0:

Works like a CDN
- Each server caches chunks that are needed by the players it's serving
- The servers keep each others' caches in sync with eachother
- The servers work together to ensure every chunk gets ticked
- Does not require BungeeCord, just some node balancing method to evenly distribute players across the servers
MultiPaper-Master
- Stores the world files and data
- Coordinates the servers
  - Decides who gets to tick the chunk (first in first served basis)
- Runs as a standalone process
  - For your convenience, it can also run as a BungeeCord plugin

How chunk syncing works:

When a server reads a chunk, it asks the Master to load the chunk from the region file. If another server has ownership of the chunk, the Master will notify the server to request the chunk from that server instead, so that it gets the most up-to-date copy.
When the server wants to tick an unowned chunk, it won't, but will instead send a request to the Master to take ownership of it. If ownership is granted, the chunk will be ticked on next tick. If ownership is denied since another server owns it, the server will keep the chunk in sync with that server.
A chunk may be loaded on a server but have no owner if it's outside the simulation distance. This is since the chunk won't be ticked by any server.
When a server has a chunk loaded into memory, it will subscribe to any changes made within that chunk. This means if any server changes a block inside the chunk, it will be updated on all servers subscribed to that chunk.

The use case

For servers that wish to maintain all vanilla mechanics while scaling up, MultiPaper is for you. Usually when a Minecraft server chooses to scale their player count up, they have to sacrifice various mechanics such as render distance, mob spawning, and redstone.

With MultiPaper, there is no need to ruin the vanilla experience. All you need are new servers when you wish to scale. Instead of having 1 server handling 100 players, you can have 10 servers handling 10 players each. This allows you to keep expensive vanilla mechanics like a large render distance, mob farms, and massive redstone contraptions.

It can scale

Perhaps 100 players isn't enough for you. You want to push the limits of your Minecraft server to the extreme with upwards of 1000 players online at once. Well, MultiPaper is also for you. With its ability to horizontally scale, the hardware's the limit.

Commands

MultiPaper includes a few commands mainly for debug purposes:

/servers
List all servers running on this MultiPaper cluster. Includes performance indicators such as TPS, tick duration, and player count.

/slist
List all online players and what server they're on.

/mpdebug
Toggle a debug visualisation showing chunks that your server is ticking (aqua) and chunks being ticked by another server (red). The server ticking the chunk you are standing in is displayed above the action bar.

/mpmap
Show a map of nearby chunks and which server owns them. Up represents north. If your server owns the chunk, the chunk is shown as aqua. If another servers owns the chunk, it's shown as red. If the chunk is in memory but not within simulation range on your server, it's shown as white. Chunks not loaded on your server as shown as grey.

Setting up MultiPaper

Download MultiPaper and MultiPaper-Master from multipaper.io
Place your worlds inside the directory being used for MultiPaper-Master
Start the MultiPaper-Master by either:
- Standalone: java -jar multipaper-master.jar <port> [optionalProxyPort]
- BungeeCord plugin: Set the port in plugins/MultiPaperProxy/config.yml
In each MultiPaper server:
- Run the server once the generate the config file multipaper.yml
- Put the name of the server used in BungeeCord's config.yml in bungeecordName
  - If you're not using BungeeCord, just make it some unique identifier
  - eg. survival1
- Put the address and port of the MultiPaper-Master in multipaperMasterAddress
  - eg. localhost:35353
- Enter the port for your local peer-to-peer server in externalServerPort
  - Leave this as 0 for it to automatically choose a port for you
  - This value can be different for each server
  - Other servers are let known of your port via MultiPaper-Master

The built-in proxy

MultiPaper provides a proxy (like Bungeecord or Velocity) that can be used to hide the multipaper servers behind a single address. The proxy automatically selects the multipaper server with the lowest load and forwards the player to it. The proxy provides no extra features and is designed to be as fast and light-weight as possible. When using the proxy, you will need to set bungeecord to true in the multipapers' spigot.yml.

This proxy is only available when running a standalone MultiPaper-Master installation and can be started by specifying a port for it to listen on:

java -jar multipaper-master.jar <port> [proxy port]

For example, to run the MultiPaper-Master on port 35353 and the proxy on port 25565, you'd run:

java -jar multipaper-master.jar 35353 25565

Using MultiPaper with plugins

For a plugin to work with MultiPaper, it needs to support multiple servers. A good indication of this, but not a guarantee, is if a plugin uses a MySQL database.

Developing a plugin for MultiPaper

To make a plugin compatible with MultiPaper, no data must be stored on the server itself and must instead be stored on an external server such as a MySQL database.

Some other things to look out for:

Caches can prevent the plugin from getting the most up-to-date data.
PlayerJoinEvent and PlayerQuitEvent will only be called on one server, however other events for the player could be called on any server.
Bukkit.broadcastMessage will send the message to all players on all MultiPaper servers.
Bukkit.getOnlinePlayers will return the players on all MultiPaper servers. You can use Player.isLocalPlayer() to determine if the player is on your server or not.

Using the MultiPaper API as a dependency

If you want your plugin to still support regular Spigot and Paper servers, we recommend using MultiLib instead.

Add the following into your build.gradle:

repositories {
  maven {
    url "https://repo.clojars.org/"
  }
}

dependencies {
  compile "com.github.puregero:multipaper-api:1.18-R0.1-SNAPSHOT"
}

Or in your pom.xml:

<repositories>
    <repository>
        <id>clojars</id>
        <url>https://repo.clojars.org/</url>
    </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>com.github.puregero</groupId>
        <artifactId>multipaper-api</artifactId>
        <version>1.18-R0.1-SNAPSHOT</version>
    </dependency>
</dependencies>

Building

Requirements:

You need git installed, with a configured user name and email. On windows you need to run from git bash.
You need jdk 17+ installed to compile (and jre 17+ to run)

Build instructions:

Patch paper with: ./gradlew applyPatches
Build the multipaper jars with: ./gradlew shadowjar createReobfPaperclipJar
Get the multipaper jar from build/libs
Get the multipaper-master jar from MultiPaper-Master/build/libs

Publishing to maven local

Publish to your local maven repository with: ./gradlew publishToMavenLocal

Licensing

All code is licensed under GPLv3 excluding MultiPaper-Master which is licensed under MIT.

Acknowledgements

MultiPaper includes optimisations from both Airplane and Pufferfish.

MultiPaper uses PaperMC's paperweight framework found here.

copyandexecute/MultiPaper