Allow custom Netty thread count

src/main/java/net/minestom/server/MinecraftServer.java

@@ -97,6 +97,7 @@ public final class MinecraftServer {
     private static PacketListenerManager packetListenerManager;
     private static PacketProcessor packetProcessor;
     private static NettyServer nettyServer;
+    private static int nettyThreadCount = Runtime.getRuntime().availableProcessors();
     private static boolean processNettyErrors = true;
 
     // In-Game Manager
@@ -626,6 +627,28 @@ public final class MinecraftServer {
         return updateManager;
     }
 
+    /**
+     * Gets the number of threads used by Netty.
+     * <p>
+     * Is the number of vCPU by default.
+     *
+     * @return the number of netty threads
+     */
+    public static int getNettyThreadCount() {
+        return nettyThreadCount;
+    }
+
+    /**
+     * Changes the number of threads used by Netty.
+     *
+     * @param nettyThreadCount the number of threads
+     * @throws IllegalStateException if the server is already started
+     */
+    public static void setNettyThreadCount(int nettyThreadCount) {
+        Check.stateCondition(started, "Netty thread count can only be changed before the server starts!");
+        MinecraftServer.nettyThreadCount = nettyThreadCount;
+    }
+
     /**
      * Gets if the server should process netty errors and other unnecessary netty events
      *
@@ -659,21 +682,27 @@ public final class MinecraftServer {
         Check.stateCondition(!initialized, "#start can only be called after #init");
         Check.stateCondition(started, "The server is already started");
 
+        MinecraftServer.started = true;
+
         LOGGER.info("Starting Minestom server.");
         MinecraftServer.responseDataConsumer = responseDataConsumer;
+
         updateManager.start();
+
+        // Init & start the TCP server
+        nettyServer.init();
         nettyServer.start(address, port);
-        long t1 = -System.nanoTime();
+
+        final long t1 = -System.nanoTime();
         // Init extensions
         // TODO: Extensions should handle depending on each other and have a load-order.
         extensionManager.getExtensions().forEach(Extension::preInitialize);
         extensionManager.getExtensions().forEach(Extension::initialize);
         extensionManager.getExtensions().forEach(Extension::postInitialize);
 
-        MinecraftServer.started = true;
-
         final double loadTime = MathUtils.round((t1 + System.nanoTime()) / 1_000_000D, 2);
         LOGGER.info("Extensions loaded in " + loadTime + "ms");
+
         LOGGER.info("Minestom server started successfully.");
     }
 

src/main/java/net/minestom/server/network/netty/NettyServer.java

@@ -22,6 +22,7 @@ import net.minestom.server.MinecraftServer;
 import net.minestom.server.network.PacketProcessor;
 import net.minestom.server.network.netty.channel.ClientChannel;
 import net.minestom.server.network.netty.codec.*;
+import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -55,15 +56,19 @@ public final class NettyServer {
     public static final String ENCODER_HANDLER_NAME = "encoder"; // Write
     public static final String CLIENT_CHANNEL_NAME = "handler"; // Read
 
-    private final EventLoopGroup boss, worker;
+    private boolean initialized = false;
-    private final ServerBootstrap bootstrap;
+
+    private PacketProcessor packetProcessor;
+
+    private EventLoopGroup boss, worker;
+    private ServerBootstrap bootstrap;
 
     private ServerSocketChannel serverChannel;
 
     private String address;
     private int port;
 
-    private final GlobalChannelTrafficShapingHandler globalTrafficHandler;
+    private GlobalChannelTrafficShapingHandler globalTrafficHandler;
 
     /**
      * Scheduler used by {@code globalTrafficHandler}.
@@ -71,32 +76,48 @@ public final class NettyServer {
     private final ScheduledExecutorService trafficScheduler = Executors.newScheduledThreadPool(1);
 
     public NettyServer(@NotNull PacketProcessor packetProcessor) {
+        this.packetProcessor = packetProcessor;
+
+        this.globalTrafficHandler = new GlobalChannelTrafficShapingHandler(trafficScheduler, 200) {
+            @Override
+            protected void doAccounting(TrafficCounter counter) {
+                // TODO proper monitoring API
+                //System.out.println("data " + counter.lastWriteThroughput() / 1000 + " " + counter.lastReadThroughput() / 1000);
+            }
+        };
+    }
+
+    public void init() {
+        Check.stateCondition(initialized, "Netty server has already been initialized!");
+        initialized = true;
+
         Class<? extends ServerChannel> channel;
+        final int workerThreadCount = MinecraftServer.getNettyThreadCount();
 
         if (IOUring.isAvailable()) {
             boss = new IOUringEventLoopGroup(2);
-            worker = new IOUringEventLoopGroup(); // thread count = core * 2
+            worker = new IOUringEventLoopGroup(workerThreadCount);
 
             channel = IOUringServerSocketChannel.class;
 
             LOGGER.info("Using io_uring");
         } else if (Epoll.isAvailable()) {
             boss = new EpollEventLoopGroup(2);
-            worker = new EpollEventLoopGroup(); // thread count = core * 2
+            worker = new EpollEventLoopGroup(workerThreadCount);
 
             channel = EpollServerSocketChannel.class;
 
             LOGGER.info("Using epoll");
         } else if (KQueue.isAvailable()) {
             boss = new KQueueEventLoopGroup(2);
-            worker = new KQueueEventLoopGroup(); // thread count = core * 2
+            worker = new KQueueEventLoopGroup(workerThreadCount);
 
             channel = KQueueServerSocketChannel.class;
 
             LOGGER.info("Using kqueue");
         } else {
             boss = new NioEventLoopGroup(2);
-            worker = new NioEventLoopGroup(); // thread count = core * 2
+            worker = new NioEventLoopGroup(workerThreadCount);
 
             channel = NioServerSocketChannel.class;
 
@@ -107,14 +128,6 @@ public final class NettyServer {
                 .group(boss, worker)
                 .channel(channel);
 
-        this.globalTrafficHandler = new GlobalChannelTrafficShapingHandler(trafficScheduler, 200) {
-            @Override
-            protected void doAccounting(TrafficCounter counter) {
-                // TODO proper monitoring API
-                //System.out.println("data " + counter.lastWriteThroughput() / 1000 + " " + counter.lastReadThroughput() / 1000);
-            }
-        };
-
 
         bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
             protected void initChannel(@NotNull SocketChannel ch) {