First tested checkpoint implementation

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

@@ -21,6 +21,7 @@ package de.steamwar.core;
 
 import com.comphenix.tinyprotocol.Reflection;
 import com.comphenix.tinyprotocol.TinyProtocol;
+import com.viaversion.viaversion.api.Via;
 import de.steamwar.sql.internal.Statement;
 import io.netty.channel.ChannelFuture;
 import org.bukkit.Bukkit;
@@ -28,22 +29,46 @@ import org.eclipse.openj9.criu.CRIUSupport;
 import org.eclipse.openj9.criu.JVMCRIUException;
 
 import java.io.DataInputStream;
+import java.io.File;
 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.Comparator;
 import java.util.List;
+import java.util.logging.Level;
+import java.util.stream.Stream;
 
 public class CheckpointUtils {
+    private 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));
+        Path path = FileSystems.getDefault().getPath(System.getProperty("checkpoint"));
+
+        try {
+            freezeInternal(path);
+        } catch (Exception e) {
+            Bukkit.shutdown();
+            throw new SecurityException(e);
+        } finally {
+            // Delete checkpoint
+            try (Stream<Path> stream = Files.walk(path)) {
+                stream.sorted(Comparator.reverseOrder()).map(Path::toFile).forEach(File::delete);
+            } catch (IOException e) {
+                //ignore
+            }
+        }
+    }
+
+    private static void freezeInternal(Path path) throws Exception {
         Statement.closeAll();
 
         // Close socket
+        Via.getManager().getInjector().uninject();
         Object serverConnection = TinyProtocol.getServerConnection(Core.getInstance());
         List<?> channels = channelFutures.get(serverConnection);
         for(Object future : channels) {
@@ -51,13 +76,13 @@ public class CheckpointUtils {
         }
         channels.clear();
 
-        // Do the snapshot
+        // Do the checkpoint
-        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.setFileLocks(true);
-        //criu.setWorkDir(path); criu.setLogFile("criu.log");
+        criu.setShellJob(true);
+        criu.setLogFile("criu.log");
         try {
             criu.checkpointJVM();
         } catch (JVMCRIUException e) {
@@ -69,9 +94,6 @@ public class CheckpointUtils {
         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
@@ -81,5 +103,8 @@ public class CheckpointUtils {
                 ((ChannelFuture) future).channel().config().setAutoRead(true);
             }
         }
+        Via.getManager().getInjector().inject();
+
+        Core.getInstance().getLogger().log(Level.INFO, "Checkpoint restored");
     }
 }