DeltaZern/paper-server/src/main/java/org/spigotmc/RestartCommand.java

package org.spigotmc;

import java.io.File;
import java.util.List;
import net.minecraft.server.MinecraftServer;
import net.minecraft.server.level.ServerPlayer;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.craftbukkit.util.CraftChatMessage;

public class RestartCommand extends Command
{

    public RestartCommand(String name)
    {
        super( name );
        this.description = "Restarts the server";
        this.usageMessage = "/restart";
        this.setPermission( "bukkit.command.restart" );
    }

    @Override
    public boolean execute(CommandSender sender, String currentAlias, String[] args)
    {
        if ( this.testPermission( sender ) )
        {
            MinecraftServer.getServer().processQueue.add( new Runnable()
            {
                @Override
                public void run()
                {
                    RestartCommand.restart();
                }
            } );
        }
        return true;
    }

    public static void restart()
    {
        RestartCommand.restart( SpigotConfig.restartScript );
    }

    private static void restart(final String restartScript)
    {
        AsyncCatcher.enabled = false; // Disable async catcher incase it interferes with us
        try
        {
            // Paper - extract method and cleanup
            boolean isRestarting = addShutdownHook( restartScript );
            if ( isRestarting )
            {
                System.out.println( "Attempting to restart with " + SpigotConfig.restartScript );
            } else
            {
                System.out.println( "Startup script '" + SpigotConfig.restartScript + "' does not exist! Stopping server." );
            }
            // Stop the watchdog
            WatchdogThread.doStop();

            shutdownServer( isRestarting );
            // Paper end
        } catch ( Exception ex )
        {
            ex.printStackTrace();
        }
    }

    // Paper start - sync copied from above with minor changes, async added
    private static void shutdownServer(boolean isRestarting)
    {
        if ( MinecraftServer.getServer().isSameThread() )
        {
            // Kick all players
            for ( ServerPlayer p : com.google.common.collect.ImmutableList.copyOf( MinecraftServer.getServer().getPlayerList().players ) )
            {
                p.connection.disconnect( CraftChatMessage.fromStringOrEmpty( SpigotConfig.restartMessage, true ) );
            }
            // Give the socket a chance to send the packets
            try
            {
                Thread.sleep( 100 );
            } catch ( InterruptedException ex )
            {
            }

            closeSocket();

            // Actually shutdown
            try
            {
                MinecraftServer.getServer().close(); // calls stop()
            } catch ( Throwable t )
            {
            }

            // Actually stop the JVM
            System.exit( 0 );

        } else
        {
            // Mark the server to shutdown at the end of the tick
            MinecraftServer.getServer().safeShutdown( false, isRestarting );

            // wait 10 seconds to see if we're actually going to try shutdown
            try
            {
                Thread.sleep( 10000 );
            }
            catch (InterruptedException ignored)
            {
            }

            // Check if we've actually hit a state where the server is going to safely shutdown
            // if we have, let the server stop as usual
            if (MinecraftServer.getServer().isStopped()) return;

            // If the server hasn't stopped by now, assume worse case and kill
            closeSocket();
            System.exit( 0 );
        }
    }
    // Paper end

    // Paper - Split from moved code
    private static void closeSocket()
    {
        // Close the socket so we can rebind with the new process
        MinecraftServer.getServer().getConnection().stop();

        // Give time for it to kick in
        try
        {
            Thread.sleep( 100 );
        } catch ( InterruptedException ex )
        {
        }
    }
    // Paper end

    // Paper start - copied from above and modified to return if the hook registered
    private static boolean addShutdownHook(String restartScript)
    {
        String[] split = restartScript.split( " " );
        if ( split.length > 0 && new File( split[0] ).isFile() )
        {
            Thread shutdownHook = new Thread()
            {
                @Override
                public void run()
                {
                    try
                    {
                        String os = System.getProperty( "os.name" ).toLowerCase(java.util.Locale.ENGLISH);
                        if ( os.contains( "win" ) )
                        {
                            Runtime.getRuntime().exec( "cmd /c start " + restartScript );
                        } else
                        {
                            Runtime.getRuntime().exec( "sh " + restartScript );
                        }
                    } catch ( Exception e )
                    {
                        e.printStackTrace();
                    }
                }
            };

            shutdownHook.setDaemon( true );
            Runtime.getRuntime().addShutdownHook( shutdownHook );
            return true;
        } else
        {
            return false;
        }
    }
    // Paper end

}