Minecraft Server Diagnostics & Engineering

Redstone & Automation Across Borders: Why Simple Chunk Cleaners Break Anarchy Worlds

Simple chunk cleaning algorithms suffer from major blind spots. Learn why cross-border actions can destroy builds and how we resolve this safely.

To maintain stable performance, many large Minecraft servers utilize chunk-cleaning tools to discard unmodified chunks. The logic is simple: if a player has not built in a chunk, let the server discard it upon unloading to prevent storage bloat.

However, standard chunk cleaners possess a **devastating blind spot**: **they only track actions occurring inside the chunk itself**.

In anarchy or technical Minecraft environments, builds are rarely self-contained. Redstone flying machines cross thousands of blocks, pistons push blocks across boundaries, water flows down slopes into adjacent chunks, and saplings grow into massive trees spilling over borders. If a chunk cleaner unloads and purges these adjacent chunks, it **wipes out player builds, breaks redstone machinery, and corrupts world data**.

The Border Cascades

To understand why standard chunk cleaners break redstone and automation, we must analyze the three classic failure cases:

1. Piston Bridges

When a piston pushed by a redstone loop extends, it moves blocks into the adjacent chunk. If the destination chunk is unmarked because the player never stood in it or placed blocks there directly, a simple cleaner will discard it upon unload. This deletes the pushed blocks, leaving the piston head floating and breaking the machine loop.

2. Fluid Flows & Cobblestone Generators

If a player places a water source that flows across a border, the fluid changes the blocks in the next chunk. When that chunk unloads, a simple cleaner purges it because no player directly placed blocks inside it. Next time the chunk loads, the flowing water disappears or behaves erratically, breaking automated cobblestone or obsidian factories.

3. Structure Growths

When a player grows a mega-spruce or dark oak tree right on a chunk boundary, the logs and leaf blocks spawn inside the adjacent chunks. Without boundary awareness, the cleaner treats these leaf and log blocks as vanilla tree generation, wipes the chunks, and splits the tree in half.

Solving the Boundary Problem

A truly safe storage optimizer must track **cross-border event propagation**. This is the core engineering design behind RetroWorldPurger.

Instead of listening to basic block placement, RetroWorldPurger implements **border-aware listeners**:

Piston Events: Tracks BlockPistonExtendEvent and BlockPistonRetractEvent. The plugin loops through all pushed blocks, flagging both the origin and destination chunks as modified.
Fluid Events: Tracks BlockFromToEvent. If water or lava crosses a border, the plugin checks if the source chunk was modified by a player. If it was, the modification state propagates to the destination chunk.
Dispenser & Projectile Events: If a dispenser fires items/fluids or an arrow strikes a button/target across a boundary, the plugin flags the target chunk.
Structure Growth Events: Monitors StructureGrowEvent, looping through all generated blocks and marking every unique chunk hosting the new structures.

MSPT Optimization on Folia

Because these listeners run constantly on high-traffic servers, they must not introduce performance overhead. RetroWorldPurger ensures **zero MSPT impact** by checking the Persistent Data Container (PDC) flag *before* performing write operations:

private void markChunk(Chunk chunk) {
    PersistentDataContainer pdc = chunk.getPersistentDataContainer();
    if (!pdc.has(MODIFIED_KEY, PersistentDataType.BYTE)) {
        pdc.set(MODIFIED_KEY, PersistentDataType.BYTE, (byte) 1);
    }
}

This short-circuit check prevents the CPU from performing expensive disk writes or database lookups repeatedly for active chunks that are already marked safe.

Conclusion

Chunk cleaning cannot be simple. By using a border-aware solution like RetroWorldPurger, server owners can safely reclaim massive amounts of disk space without the fear of breaking player bases, automated farms, or redstone setups.