Allow server to be stopped cleanly

src/main/java/fr/themode/demo/Main.java

@@ -15,6 +15,7 @@ import net.minestom.server.item.Material;
 import net.minestom.server.network.packet.server.play.DeclareRecipesPacket;
 import net.minestom.server.recipe.RecipeManager;
 import net.minestom.server.recipe.ShapelessRecipe;
+import net.minestom.server.timer.TaskRunnable;
 import net.minestom.server.utils.time.TimeUnit;
 import net.minestom.server.utils.time.UpdateOption;
 
@@ -50,6 +51,13 @@ public class Main {
 
         MinecraftServer.getBenchmarkManager().enable(new UpdateOption(10 * 1000, TimeUnit.MILLISECOND));
 
+        MinecraftServer.getSchedulerManager().addShutdownTask(new TaskRunnable() {
+            @Override
+            public void run() {
+                System.out.println("Good night");
+            }
+        });
+
         PlayerInit.init();
 
         minecraftServer.start("localhost", 55555, PlayerInit.getResponseDataConsumer());

src/main/java/fr/themode/demo/commands/SimpleCommand.java

@@ -1,5 +1,6 @@
 package fr.themode.demo.commands;
 
+import net.minestom.server.MinecraftServer;
 import net.minestom.server.command.CommandProcessor;
 import net.minestom.server.entity.EntityCreature;
 import net.minestom.server.entity.Player;
@@ -26,6 +27,8 @@ public class SimpleCommand implements CommandProcessor {
             creature.setPathTo(player.getPosition());
         }
 
+        MinecraftServer.stopCleanly();
+
 
         return true;
     }

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

@@ -187,4 +187,13 @@ public class MinecraftServer {
         nettyServer.start(address, port);
     }
 
+    /**
+     * Stops this server properly (saves if needed, kicking players, etc.)
+     */
+    public static void stopCleanly() {
+        updateManager.stop();
+        nettyServer.stop();
+        schedulerManager.shutdown();
+    }
+
 }

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

@@ -13,6 +13,7 @@ import java.util.concurrent.ExecutorService;
 public class UpdateManager {
 
     private ExecutorService mainUpdate = new MinestomThread(MinecraftServer.THREAD_COUNT_MAIN_UPDATE, MinecraftServer.THREAD_NAME_MAIN_UPDATE);
+    private boolean stopRequested;
 
 
     public void start() {
@@ -25,7 +26,7 @@ public class UpdateManager {
 
             final long tickDistance = MinecraftServer.TICK_MS * 1000000;
             long currentTime;
-            while (true) {
+            while (!stopRequested) {
                 currentTime = System.nanoTime();
 
                 // Keep Alive Handling
@@ -63,4 +64,7 @@ public class UpdateManager {
         });
     }
 
+    public void stop() {
+        stopRequested = true;
+    }
 }

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

@@ -1,6 +1,7 @@
 package net.minestom.server.network.netty;
 
 import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelInitializer;
 import io.netty.channel.EventLoopGroup;
@@ -62,4 +63,12 @@ public class NettyServer {
     public int getPort() {
         return port;
     }
+
+    public void stop() {
+        try {
+            group.shutdownGracefully().sync();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
 }

src/main/java/net/minestom/server/timer/SchedulerManager.java

@@ -13,8 +13,10 @@ import java.util.concurrent.atomic.AtomicInteger;
 public class SchedulerManager {
 
     private static final AtomicInteger COUNTER = new AtomicInteger();
+    private static final AtomicInteger SHUTDOWN_COUNTER = new AtomicInteger();
     private static ExecutorService batchesPool = new MinestomThread(MinecraftServer.THREAD_COUNT_SCHEDULER, MinecraftServer.THREAD_NAME_SCHEDULER);
     private List<Task> tasks = new CopyOnWriteArrayList<>();
+    private List<Task> shutdownTasks = new CopyOnWriteArrayList<>();
 
     public int addTask(TaskRunnable runnable, UpdateOption updateOption, int maxCallCount) {
         int id = COUNTER.incrementAndGet();
@@ -34,6 +36,29 @@ public class SchedulerManager {
         return addTask(runnable, updateOption, 1);
     }
 
+    /**
+     * Adds a task to run when the server shutdowns
+     * @param runnable the task to perform
+     * @return
+     */
+    public int addShutdownTask(TaskRunnable runnable) {
+        int id = SHUTDOWN_COUNTER.incrementAndGet();
+        runnable.setId(id);
+
+        Task task = new Task(runnable, null, 1);
+        this.shutdownTasks.add(task);
+
+        return id;
+    }
+
+    public void shutdown() {
+        batchesPool.execute(() -> {
+            for (Task task : shutdownTasks) {
+                task.getRunnable().run();
+            }
+        });
+    }
+
     public void removeTask(int taskId) {
         this.tasks.removeIf(task -> task.getId() == taskId);
     }