First untested checkpoint implementation

SpigotCore_Main/src/com/comphenix/tinyprotocol/TinyProtocol.java

@@ -28,8 +28,11 @@ public class TinyProtocol implements Listener {
 	private static final Class<?> playerList = Reflection.getClass("{nms.server.players}.PlayerList");
 	private static final Class<?> minecraftServer = Reflection.getClass("{nms.server}.MinecraftServer");
 	private static final FieldAccessor<?> getMinecraftServer = Reflection.getField(playerList, minecraftServer, 0);
-	private static final Class<?> serverConnection = Reflection.getClass("{nms.server.network}.ServerConnection");
+	public static final Class<?> serverConnection = Reflection.getClass("{nms.server.network}.ServerConnection");
 	private static final FieldAccessor<?> getServerConnection = Reflection.getField(minecraftServer, serverConnection, 0);
+	public static Object getServerConnection(Plugin plugin) {
+		return getServerConnection.get(getMinecraftServer.get(getPlayerList.get(plugin.getServer())));
+	}
 	private static final Class<?> networkManager = Reflection.getClass("{nms.network}.NetworkManager");
 	private static final FieldAccessor<List> getConnections = Reflection.getField(serverConnection, List.class, 0, networkManager);
 
@@ -51,7 +54,7 @@ public class TinyProtocol implements Listener {
 	private TinyProtocol(final Plugin plugin) {
 		this.plugin = plugin;
 		this.handlerName = "tiny-" + plugin.getName() + "-" + ++id;
-		this.connections = getConnections.get(getServerConnection.get(getMinecraftServer.get(getPlayerList.get(plugin.getServer()))));
+		this.connections = getConnections.get(getServerConnection(plugin));
 
 		plugin.getServer().getPluginManager().registerEvents(this, plugin);
 

SpigotCore_Main/src/de/steamwar/core/CheckpointUtils.java

@@ -0,0 +1,85 @@
+/*
+ *   This file is a part of the SteamWar software.
+ *
+ *   Copyright (C) 2024  SteamWar.de-Serverteam
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU Affero General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU Affero General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Affero General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.steamwar.core;
+
+import com.comphenix.tinyprotocol.Reflection;
+import com.comphenix.tinyprotocol.TinyProtocol;
+import de.steamwar.sql.internal.Statement;
+import io.netty.channel.ChannelFuture;
+import org.bukkit.Bukkit;
+import org.eclipse.openj9.criu.CRIUSupport;
+import org.eclipse.openj9.criu.JVMCRIUException;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.net.InetAddress;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+public class CheckpointUtils {
+    private static final Reflection.FieldAccessor<List> channelFutures = Reflection.getField(TinyProtocol.serverConnection, List.class, 0, ChannelFuture.class);
+    private static final Reflection.MethodInvoker bind = Reflection.getMethod(TinyProtocol.serverConnection, null, InetAddress.class, int.class);
+
+    public static void freeze() {
+        Bukkit.getOnlinePlayers().forEach(player -> player.kickPlayer(null));
+        Statement.closeAll();
+
+        // Close socket
+        Object serverConnection = TinyProtocol.getServerConnection(Core.getInstance());
+        List<?> channels = channelFutures.get(serverConnection);
+        for(Object future : channels) {
+            ((ChannelFuture) future).channel().close().syncUninterruptibly();
+        }
+        channels.clear();
+
+        // Do the snapshot
+        Path path = FileSystems.getDefault().getPath("/tmp/checkpoints/" + Core.getVersion() + "/" + Bukkit.getWorlds().get(0).getName());
+        path.toFile().mkdirs();
+        CRIUSupport criu = new CRIUSupport(path);
+        criu.setAutoDedup(true);
+        //criu.setShellJob(true);
+        //criu.setWorkDir(path); criu.setLogFile("criu.log");
+        try {
+            criu.checkpointJVM();
+        } catch (JVMCRIUException e) {
+            Bukkit.shutdown();
+            throw e;
+        }
+
+        // Get new port
+        int port;
+        try (DataInputStream stream = new DataInputStream(Files.newInputStream(path.resolve("port").toFile().toPath()))) {
+            port = stream.readInt();
+        } catch (IOException e) {
+            Bukkit.shutdown();
+            throw new SecurityException(e);
+        }
+
+        // Reopen socket
+        bind.invoke(serverConnection, InetAddress.getLoopbackAddress(), port);
+        if(Core.getVersion() > 12) {
+            for(Object future : channels) {
+                ((ChannelFuture) future).channel().config().setAutoRead(true);
+            }
+        }
+    }
+}