refactor: Fix concurrency issues when sending packets

Also changed light updates to be handled on the server world chunk manager's thread pool instead of the common thread pool, discarded chunks that generated an exception during world generation, and increased the server world chunk manager's thread pool to 8 threads.

common/src/main/java/io/github/steveplays28/noisium/experimental/server/player/NoisiumServerPlayerChunkLoader.java

@@ -51,7 +51,7 @@ public NoisiumServerPlayerChunkLoader() {
 	@SuppressWarnings("ForLoopReplaceableByForEach")
 	private void tick(@NotNull ServerWorld serverWorld, @NotNull BiFunction<ChunkPos, Integer, Map<ChunkPos, CompletableFuture<WorldChunk>>> worldChunksSupplier) {
 		var players = serverWorld.getPlayers();
-		if (players.size() == 0 || previousPlayerPositions.size() == 0) {
+		if (players.isEmpty() || previousPlayerPositions.isEmpty()) {
 			return;
 		}
 
@@ -61,7 +61,7 @@ private void tick(@NotNull ServerWorld serverWorld, @NotNull BiFunction<ChunkPos
 			if (!playerBlockPos.isWithinDistance(previousPlayerPositions.get(player.getId()), 16d)) {
 				var worldChunks = worldChunksSupplier.apply(new ChunkPos(playerBlockPos), 6);
 
-				ChunkUtil.sendWorldChunksToPlayerAsync(serverWorld, new ArrayList<>(worldChunks.values()));
+				ChunkUtil.sendWorldChunksToPlayerAsync(serverWorld, new ArrayList<>(worldChunks.values()), threadPoolExecutor);
 				CompletableFuture.runAsync(() -> player.networkHandler.sendPacket(
 						new ChunkRenderDistanceCenterS2CPacket(
 								ChunkSectionPos.getSectionCoord(playerBlockPos.getX()),

common/src/main/java/io/github/steveplays28/noisium/experimental/server/world/NoisiumServerWorldChunkManager.java

@@ -64,7 +64,7 @@ public NoisiumServerWorldChunkManager(@NotNull ServerWorld serverWorld, @NotNull
 				worldDirectoryPath.resolve("poi"), dataFixer, true, serverWorld.getRegistryManager(), serverWorld);
 		this.versionedChunkStorage = new NoisiumServerVersionedChunkStorage(worldDirectoryPath.resolve("region"), dataFixer, true);
 		this.threadPoolExecutor = Executors.newFixedThreadPool(
-				1, new ThreadFactoryBuilder().setNameFormat("Noisium Server World Chunk Manager %d").build());
+				8, new ThreadFactoryBuilder().setNameFormat("Noisium Server World Chunk Manager %d").build());
 		this.loadingWorldChunks = new ConcurrentHashMap<>();
 		this.loadedWorldChunks = new HashMap<>();
 
@@ -120,6 +120,8 @@ public NoisiumServerWorldChunkManager(@NotNull ServerWorld serverWorld, @NotNull
 		}, threadPoolExecutor).whenComplete((fetchedWorldChunk, throwable) -> {
 			if (throwable != null) {
 				Noisium.LOGGER.error("Exception thrown while getting a chunk asynchronously:\n{}", ExceptionUtils.getStackTrace(throwable));
+				loadingWorldChunks.remove(chunkPos);
+				return;
 			}
 
 			fetchedWorldChunk.addChunkTickSchedulers(serverWorld);
@@ -214,6 +216,7 @@ public boolean isChunkLoaded(ChunkPos chunkPos) {
 		return this.loadedWorldChunks.containsKey(chunkPos);
 	}
 
+	// TODO: Move into the ServerLightingProvider
 	/**
 	 * Updates the chunk's lighting at the specified {@link ChunkSectionPos}.
 	 * This method is ran asynchronously.
@@ -224,9 +227,8 @@ public boolean isChunkLoaded(ChunkPos chunkPos) {
 	private void onLightUpdateAsync(@NotNull LightType lightType, @NotNull ChunkSectionPos chunkSectionPosition) {
 		var lightingProvider = serverWorld.getLightingProvider();
 		int bottomY = lightingProvider.getBottomY();
-		int topY = lightingProvider.getTopY();
 		var chunkSectionYPosition = chunkSectionPosition.getSectionY();
-		if (chunkSectionYPosition < bottomY || chunkSectionYPosition > topY) {
+		if (chunkSectionYPosition < bottomY || chunkSectionYPosition > lightingProvider.getTopY()) {
 			return;
 		}
 
@@ -245,7 +247,7 @@ private void onLightUpdateAsync(@NotNull LightType lightType, @NotNull ChunkSect
 				blockLightBits.set(chunkSectionYPositionDifference);
 			}
 			ChunkUtil.sendLightUpdateToPlayers(serverWorld.getPlayers(), lightingProvider, chunkPosition, skyLightBits, blockLightBits);
-		});
+		}, threadPoolExecutor);
 	}
 
 	// TODO: Check if this can be ran asynchronously

common/src/main/java/io/github/steveplays28/noisium/experimental/util/world/chunk/ChunkUtil.java

@@ -1,6 +1,7 @@
 package io.github.steveplays28.noisium.experimental.util.world.chunk;
 
 import net.minecraft.block.BlockState;
+import net.minecraft.network.NetworkThreadUtils;
 import net.minecraft.network.packet.s2c.play.BlockUpdateS2CPacket;
 import net.minecraft.network.packet.s2c.play.ChunkDataS2CPacket;
 import net.minecraft.network.packet.s2c.play.LightUpdateS2CPacket;
@@ -15,6 +16,7 @@
 import java.util.BitSet;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
 
 public class ChunkUtil {
 	/**
@@ -54,10 +56,10 @@ public static void sendWorldChunksToPlayer(@NotNull ServerWorld serverWorld, @No
 	 * @param worldChunkFutures The {@link List} of {@link CompletableFuture<WorldChunk>}s
 	 */
 	@SuppressWarnings("ForLoopReplaceableByForEach")
-	public static void sendWorldChunksToPlayerAsync(@NotNull ServerWorld serverWorld, @NotNull List<CompletableFuture<WorldChunk>> worldChunkFutures) {
+	public static void sendWorldChunksToPlayerAsync(@NotNull ServerWorld serverWorld, @NotNull List<CompletableFuture<WorldChunk>> worldChunkFutures, @NotNull Executor executor) {
 		// TODO: Send a whole batch of chunks to the player at once to save on network traffic
 		for (int i = 0; i < worldChunkFutures.size(); i++) {
-			worldChunkFutures.get(i).whenCompleteAsync((worldChunk, throwable) -> sendWorldChunkToPlayer(serverWorld, worldChunk));
+			worldChunkFutures.get(i).whenCompleteAsync((worldChunk, throwable) -> sendWorldChunkToPlayer(serverWorld, worldChunk), executor);
 		}
 	}