From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 12 Apr 2020 15:50:48 -0400
Subject: [PATCH] Improved Watchdog Support

Forced Watchdog Crash support and Improve Async Shutdown

If the request to shut down the server is received while we are in
a watchdog hang, immediately treat it as a crash and begin the shutdown
process. Shutdown process is now improved to also shutdown cleanly when
not using restart scripts either.

If a server is deadlocked, a server owner can send SIGUP (or any other signal
the JVM understands to shut down as it currently does) and the watchdog
will no longer need to wait until the full timeout, allowing you to trigger
a close process and try to shut the server down gracefully, saving player and
world data.

Previously there was no way to trigger this outside of waiting for a full watchdog
timeout, which may be set to a really long time...

Additionally, fix everything to do with shutting the server down asynchronously.

Previously, nearly everything about the process was fragile and unsafe. Main might
not have actually been frozen, and might still be manipulating state.

Or, some reuest might ask main to do something in the shutdown but main is dead.

Or worse, other things might start closing down items such as the Console or Thread Pool
before we are fully shutdown.

This change tries to resolve all of these issues by moving everything into the stop
method and guaranteeing only one thread is stopping the server.

We then issue Thread Death to the main thread of another thread initiates the stop process.
We have to ensure Thread Death propagates correctly though to stop main completely.

This is to ensure that if main isn't truely stuck, it's not manipulating state we are trying to save.

This also moves all plugins who register "delayed init" tasks to occur just before "Done" so they
are properly accounted for and wont trip watchdog on init.

diff --git a/src/main/java/com/destroystokyo/paper/Metrics.java b/src/main/java/com/destroystokyo/paper/Metrics.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/com/destroystokyo/paper/Metrics.java
+++ b/src/main/java/com/destroystokyo/paper/Metrics.java
@@ -0,0 +0,0 @@ public class Metrics {
      * Starts the Scheduler which submits our data every 30 minutes.
      */
     private void startSubmitting() {
-        final Runnable submitTask = this::submitData;
+        final Runnable submitTask = () -> {
+            if (MinecraftServer.getServer().hasStopped()) {
+                return;
+            }
+            submitData();
+        };
 
         // Many servers tend to restart at a fixed time at xx:00 which causes an uneven distribution of requests on the
         // bStats backend. To circumvent this problem, we introduce some randomness into the initial and second delay.
diff --git a/src/main/java/net/minecraft/CrashReport.java b/src/main/java/net/minecraft/CrashReport.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/CrashReport.java
+++ b/src/main/java/net/minecraft/CrashReport.java
@@ -0,0 +0,0 @@ public class CrashReport {
     }
 
     public static CrashReport forThrowable(Throwable cause, String title) {
+        if (cause instanceof ThreadDeath) com.destroystokyo.paper.util.SneakyThrow.sneaky(cause); // Paper
         while (cause instanceof CompletionException && cause.getCause() != null) {
             cause = cause.getCause();
         }
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public java.util.Queue<Runnable> processQueue = new java.util.concurrent.ConcurrentLinkedQueue<Runnable>();
     public int autosavePeriod;
     public Commands vanillaCommandDispatcher;
-    private boolean forceTicks;
+    public boolean forceTicks; // Paper
     // CraftBukkit end
     // Spigot start
     public static final int TPS = 20;
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     // Spigot end
     public static long currentTickLong = 0L; // Paper
 
+    public volatile Thread shutdownThread; // Paper
+    public volatile boolean abnormalExit = false; // Paper
+
     public static <S extends MinecraftServer> S spin(Function<Thread, S> serverFactory) {
         AtomicReference<S> atomicreference = new AtomicReference();
         Thread thread = new Thread(() -> {
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     // CraftBukkit start
     private boolean hasStopped = false;
+    public volatile boolean hasFullyShutdown = false; // Paper
     private final Object stopLock = new Object();
     public final boolean hasStopped() {
         synchronized (this.stopLock) {
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             if (this.hasStopped) return;
             this.hasStopped = true;
         }
+        // Paper start - kill main thread, and kill it hard
+        shutdownThread = Thread.currentThread();
+        org.spigotmc.WatchdogThread.doStop(); // Paper
+        if (!isSameThread()) {
+            MinecraftServer.LOGGER.info("Stopping main thread (Ignore any thread death message you see! - DO NOT REPORT THREAD DEATH TO PAPER)");
+            while (this.getRunningThread().isAlive()) {
+                this.getRunningThread().stop();
+                try {
+                    Thread.sleep(1);
+                } catch (InterruptedException e) {}
+            }
+        }
+        // Paper end
         // CraftBukkit end
         MinecraftServer.LOGGER.info("Stopping server");
         MinecraftTimings.stopServer(); // Paper
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             this.getProfileCache().save(false); // Paper
         }
         // Spigot end
+        // Paper start - move final shutdown items here
+        LOGGER.info("Flushing Chunk IO");
         com.destroystokyo.paper.io.PaperFileIOThread.Holder.INSTANCE.close(true, true); // Paper
+        LOGGER.info("Closing Thread Pool");
+        Util.shutdownExecutors(); // Paper
+        LOGGER.info("Closing Server");
+        try {
+            net.minecrell.terminalconsole.TerminalConsoleAppender.close(); // Paper - Use TerminalConsoleAppender
+        } catch (Exception e) {
+        }
+        this.onServerExit();
+        // Paper end
     }
 
     public String getLocalIp() {
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     protected void runServer() {
         try {
+            long serverStartTime = Util.getNanos(); // Paper
             if (this.initServer()) {
                 this.nextTickTime = Util.getMillis();
                 this.status.setDescription(new TextComponent(this.motd));
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                 this.updateStatusIcon(this.status);
 
                 // Spigot start
+                // Paper start - move done tracking
+                LOGGER.info("Running delayed init tasks");
+                this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // run all 1 tick delay tasks during init,
+                // this is going to be the first thing the tick process does anyways, so move done and run it after
+                // everything is init before watchdog tick.
+                // anything at 3+ won't be caught here but also will trip watchdog....
+                // tasks are default scheduled at -1 + delay, and first tick will tick at 1
+                String doneTime = String.format(java.util.Locale.ROOT, "%.3fs", (double) (Util.getNanos() - serverStartTime) / 1.0E9D);
+                LOGGER.info("Done ({})! For help, type \"help\"", doneTime);
+                // Paper end
+
+                org.spigotmc.WatchdogThread.tick(); // Paper
                 org.spigotmc.WatchdogThread.hasStarted = true; // Paper
                 Arrays.fill( recentTps, 20 );
                 long start = System.nanoTime(), curTime, tickSection = start; // Paper - Further improve server tick loop
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                 this.onServerCrash((CrashReport) null);
             }
         } catch (Throwable throwable) {
+            // Paper start
+            if (throwable instanceof ThreadDeath) {
+                MinecraftServer.LOGGER.error("Main thread terminated by WatchDog due to hard crash", throwable);
+                return;
+            }
+            // Paper end
             MinecraftServer.LOGGER.error("Encountered an unexpected exception", throwable);
             // Spigot Start
             if ( throwable.getCause() != null )
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             } catch (Throwable throwable1) {
                 MinecraftServer.LOGGER.error("Exception stopping the server", throwable1);
             } finally {
-                org.spigotmc.WatchdogThread.doStop(); // Spigot
+                //org.spigotmc.WatchdogThread.doStop(); // Spigot // Paper - move into stop
                 // CraftBukkit start - Restore terminal to original settings
                 try {
-                    net.minecrell.terminalconsole.TerminalConsoleAppender.close(); // Paper - Use TerminalConsoleAppender
+                    //net.minecrell.terminalconsole.TerminalConsoleAppender.close(); // Paper - Move into stop
                 } catch (Exception ignored) {
                 }
                 // CraftBukkit end
-                this.onServerExit();
+                //this.exit(); // Paper - moved into stop
             }
 
         }
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     @Override
     public TickTask wrapRunnable(Runnable runnable) {
+        // Paper start - anything that does try to post to main during watchdog crash, run on watchdog
+        if (this.hasStopped && Thread.currentThread().equals(shutdownThread)) {
+            runnable.run();
+            runnable = () -> {};
+        }
+        // Paper end
         return new TickTask(this.tickCount, runnable);
     }
 
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                 try {
                     crashreport = CrashReport.forThrowable(throwable, "Exception ticking world");
                 } catch (Throwable t) {
+                    if (throwable instanceof ThreadDeath) { throw (ThreadDeath)throwable; } // Paper
                     throw new RuntimeException("Error generating crash report", t);
                 }
                 // Spigot End
@@ -0,0 +0,0 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             this.packRepository.setSelected(datapacks);
             this.worldData.setDataPackConfig(MinecraftServer.getSelectedPacks(this.packRepository));
             datapackresources.updateGlobals();
-            this.getPlayerList().saveAll();
+            if (Thread.currentThread() != this.serverThread) return; // Paper
+            //this.getPlayerList().savePlayers(); // Paper - we don't need to do this
             this.getPlayerList().reloadResources();
             this.functionManager.replaceLibrary(this.resources.getFunctionLibrary());
             this.structureManager.onResourceManagerReload(this.resources.getResourceManager());
diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -0,0 +0,0 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
             long j = Util.getNanos() - i;
             String s = String.format(Locale.ROOT, "%.3fs", (double) j / 1.0E9D);
 
-            DedicatedServer.LOGGER.info("Done ({})! For help, type \"help\"", s);
+            //DedicatedServer.LOGGER.info("Done ({})! For help, type \"help\"", s); // Paper moved to after init
             if (dedicatedserverproperties.announcePlayerAchievements != null) {
                 ((GameRules.BooleanValue) this.getGameRules().getRule(GameRules.RULE_ANNOUNCE_ADVANCEMENTS)).set(dedicatedserverproperties.announcePlayerAchievements, (MinecraftServer) this);
             }
@@ -0,0 +0,0 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
             //this.remoteStatusListener.b(); // Paper - don't wait for remote connections
         }
 
-        System.exit(0); // CraftBukkit
+        hasFullyShutdown = true; // Paper
+        System.exit(this.abnormalExit ? 70 : 0); // CraftBukkit // Paper
     }
 
     @Override
@@ -0,0 +0,0 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
     @Override
     public void stopServer() {
         super.stopServer();
-        Util.shutdownExecutors();
+        //SystemUtils.h(); // Paper - moved into super
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -0,0 +0,0 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             MutableBoolean mutableboolean = new MutableBoolean();
 
             do {
+                boolean isShuttingDown = level.getServer().hasStopped(); // Paper
                 mutableboolean.setFalse();
                 list.stream().map((playerchunk) -> {
                     CompletableFuture completablefuture;
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -0,0 +0,0 @@ public abstract class PlayerList {
         this.cserver.getPluginManager().callEvent(playerQuitEvent);
         entityplayer.getBukkitEntity().disconnect(playerQuitEvent.getQuitMessage());
 
-        entityplayer.doTick(); // SPIGOT-924
+        if (server.isSameThread()) entityplayer.doTick(); // SPIGOT-924 // Paper - don't tick during emergency shutdowns (Watchdog)
         // CraftBukkit end
 
         // Paper start - Remove from collideRule team if needed
diff --git a/src/main/java/net/minecraft/util/thread/BlockableEventLoop.java b/src/main/java/net/minecraft/util/thread/BlockableEventLoop.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/util/thread/BlockableEventLoop.java
+++ b/src/main/java/net/minecraft/util/thread/BlockableEventLoop.java
@@ -0,0 +0,0 @@ public abstract class BlockableEventLoop<R extends Runnable> implements Profiler
         try {
             task.run();
         } catch (Exception var3) {
+            if (var3.getCause() instanceof ThreadDeath) throw var3; // Paper
             LOGGER.fatal("Error executing task on {}", this.name(), var3);
         }
 
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -0,0 +0,0 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         try {
             tickConsumer.accept(entity);
         } catch (Throwable throwable) {
+            if (throwable instanceof ThreadDeath) throw throwable; // Paper
             // Paper start - Prevent tile entity and entity crashes
             final String msg = String.format("Entity threw exception at %s:%s,%s,%s", entity.level.getWorld().getName(), entity.getX(), entity.getY(), entity.getZ());
             MinecraftServer.LOGGER.error(msg, throwable);
diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -0,0 +0,0 @@ public class LevelChunk implements ChunkAccess {
 
                         gameprofilerfiller.pop();
                     } catch (Throwable throwable) {
+                        if (throwable instanceof ThreadDeath) throw throwable; // Paper
                         // Paper start - Prevent tile entity and entity crashes
                         final String msg = String.format("BlockEntity threw exception at %s:%s,%s,%s", LevelChunk.this.getLevel().getWorld().getName(), this.getPos().getX(), this.getPos().getY(), this.getPos().getZ());
                         net.minecraft.server.MinecraftServer.LOGGER.error(msg, throwable);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -0,0 +0,0 @@ public final class CraftServer implements Server {
 
     @Override
     public boolean isPrimaryThread() {
-        return Thread.currentThread().equals(console.serverThread); // Paper - Fix issues with detecting main thread properly
+        return Thread.currentThread().equals(console.serverThread) || Thread.currentThread().equals(net.minecraft.server.MinecraftServer.getServer().shutdownThread); // Paper - Fix issues with detecting main thread properly, the only time Watchdog will be used is during a crash shutdown which is a "try our best" scenario
     }
 
     // Paper start
diff --git a/src/main/java/org/bukkit/craftbukkit/Main.java b/src/main/java/org/bukkit/craftbukkit/Main.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/Main.java
+++ b/src/main/java/org/bukkit/craftbukkit/Main.java
@@ -0,0 +0,0 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 import joptsimple.OptionParser;
 import joptsimple.OptionSet;
+import net.minecraft.util.ExceptionCollector;
+import net.minecraft.world.level.lighting.LayerLightEventListener;
 import net.minecrell.terminalconsole.TerminalConsoleAppender; // Paper
 
 public class Main {
@@ -0,0 +0,0 @@ public class Main {
 
         OptionSet options = null;
 
+        // Paper start - preload logger classes to avoid plugins mixing versions
+        tryPreloadClass("org.apache.logging.log4j.core.Core");
+        tryPreloadClass("org.apache.logging.log4j.core.appender.AsyncAppender");
+        tryPreloadClass("org.apache.logging.log4j.core.Appender");
+        tryPreloadClass("org.apache.logging.log4j.core.ContextDataInjector");
+        tryPreloadClass("org.apache.logging.log4j.core.Filter");
+        tryPreloadClass("org.apache.logging.log4j.core.ErrorHandler");
+        tryPreloadClass("org.apache.logging.log4j.core.LogEvent");
+        tryPreloadClass("org.apache.logging.log4j.core.Logger");
+        tryPreloadClass("org.apache.logging.log4j.core.LoggerContext");
+        tryPreloadClass("org.apache.logging.log4j.core.LogEventListener");
+        tryPreloadClass("org.apache.logging.log4j.core.AbstractLogEvent");
+        tryPreloadClass("org.apache.logging.log4j.message.AsynchronouslyFormattable");
+        tryPreloadClass("org.apache.logging.log4j.message.FormattedMessage");
+        tryPreloadClass("org.apache.logging.log4j.message.ParameterizedMessage");
+        tryPreloadClass("org.apache.logging.log4j.message.Message");
+        tryPreloadClass("org.apache.logging.log4j.message.MessageFactory");
+        tryPreloadClass("org.apache.logging.log4j.message.TimestampMessage");
+        tryPreloadClass("org.apache.logging.log4j.message.SimpleMessage");
+        tryPreloadClass("org.apache.logging.log4j.core.async.AsyncLogger");
+        tryPreloadClass("org.apache.logging.log4j.core.async.AsyncLoggerContext");
+        tryPreloadClass("org.apache.logging.log4j.core.async.AsyncQueueFullPolicy");
+        tryPreloadClass("org.apache.logging.log4j.core.async.AsyncLoggerDisruptor");
+        tryPreloadClass("org.apache.logging.log4j.core.async.RingBufferLogEvent");
+        tryPreloadClass("org.apache.logging.log4j.core.async.DisruptorUtil");
+        tryPreloadClass("org.apache.logging.log4j.core.async.RingBufferLogEventHandler");
+        tryPreloadClass("org.apache.logging.log4j.core.impl.ThrowableProxy");
+        tryPreloadClass("org.apache.logging.log4j.core.impl.ExtendedClassInfo");
+        tryPreloadClass("org.apache.logging.log4j.core.impl.ExtendedStackTraceElement");
+        // Paper end
         try {
             options = parser.parse(args);
         } catch (joptsimple.OptionException ex) {
@@ -0,0 +0,0 @@ public class Main {
             } catch (Throwable t) {
                 t.printStackTrace();
             }
+            // Paper start
+            // load some required classes to avoid errors during shutdown if jar is replaced
+            // also to guarantee our version loads over plugins
+            tryPreloadClass("com.destroystokyo.paper.util.SneakyThrow");
+            tryPreloadClass("com.google.common.collect.Iterators$PeekingImpl");
+            tryPreloadClass("com.google.common.collect.MapMakerInternalMap$Values");
+            tryPreloadClass("com.google.common.collect.MapMakerInternalMap$ValueIterator");
+            tryPreloadClass("com.google.common.collect.MapMakerInternalMap$WriteThroughEntry");
+            tryPreloadClass("com.google.common.collect.Iterables");
+            for (int i = 1; i <= 15; i++) {
+                tryPreloadClass("com.google.common.collect.Iterables$" + i, false);
+            }
+            tryPreloadClass("org.apache.commons.lang3.mutable.MutableBoolean");
+            tryPreloadClass("org.apache.commons.lang3.mutable.MutableInt");
+            tryPreloadClass("org.jline.terminal.impl.MouseSupport");
+            tryPreloadClass("org.jline.terminal.impl.MouseSupport$1");
+            tryPreloadClass("org.jline.terminal.Terminal$MouseTracking");
+            tryPreloadClass("co.aikar.timings.TimingHistory");
+            tryPreloadClass("co.aikar.timings.TimingHistory$MinuteReport");
+            tryPreloadClass("io.netty.channel.AbstractChannelHandlerContext");
+            tryPreloadClass("io.netty.channel.AbstractChannelHandlerContext$11");
+            tryPreloadClass("io.netty.channel.AbstractChannelHandlerContext$12");
+            tryPreloadClass("io.netty.channel.AbstractChannel$AbstractUnsafe$8");
+            tryPreloadClass("io.netty.util.concurrent.DefaultPromise");
+            tryPreloadClass("io.netty.util.concurrent.DefaultPromise$1");
+            tryPreloadClass("io.netty.util.internal.PromiseNotificationUtil");
+            tryPreloadClass("io.netty.util.internal.SystemPropertyUtil");
+            tryPreloadClass("org.bukkit.craftbukkit.scheduler.CraftScheduler");
+            tryPreloadClass("org.bukkit.craftbukkit.scheduler.CraftScheduler$1");
+            tryPreloadClass("org.bukkit.craftbukkit.scheduler.CraftScheduler$2");
+            tryPreloadClass("org.bukkit.craftbukkit.scheduler.CraftScheduler$3");
+            tryPreloadClass("org.bukkit.craftbukkit.scheduler.CraftScheduler$4");
+            tryPreloadClass("org.slf4j.helpers.MessageFormatter");
+            tryPreloadClass("org.slf4j.helpers.FormattingTuple");
+            tryPreloadClass("org.slf4j.helpers.BasicMarker");
+            tryPreloadClass("org.slf4j.helpers.Util");
+            tryPreloadClass("com.destroystokyo.paper.event.player.PlayerConnectionCloseEvent");
+            tryPreloadClass("com.destroystokyo.paper.event.entity.EntityRemoveFromWorldEvent");
+            // Minecraft, seen during saving
+            tryPreloadClass(LayerLightEventListener.DummyLightLayerEventListener.class.getName());
+            tryPreloadClass(LayerLightEventListener.class.getName());
+            tryPreloadClass(ExceptionCollector.class.getName());
+            // Paper end
+        }
+    }
+
+    // Paper start
+    private static void tryPreloadClass(String className) {
+        tryPreloadClass(className, true);
+    }
+    private static void tryPreloadClass(String className, boolean printError) {
+        try {
+            Class.forName(className);
+        } catch (ClassNotFoundException e) {
+            if (printError) System.err.println("An expected class  " + className + " was not found for preloading: " + e.getMessage());
         }
     }
+    // Paper end
 
     private static List<String> asList(String... params) {
         return Arrays.asList(params);
diff --git a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
@@ -0,0 +0,0 @@ public class ServerShutdownThread extends Thread {
     @Override
     public void run() {
         try {
+            // Paper start - try to shutdown on main
+            server.safeShutdown(false, false);
+            for (int i = 1000; i > 0 && !server.hasStopped(); i -= 100) {
+                Thread.sleep(100);
+            }
+            if (server.hasStopped()) {
+                while (!server.hasFullyShutdown) Thread.sleep(1000);
+                return;
+            }
+            // Looks stalled, close async
             org.spigotmc.AsyncCatcher.enabled = false; // Spigot
             org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper
+            server.forceTicks = true;
             this.server.close();
+            while (!server.hasFullyShutdown) Thread.sleep(1000);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+            // Paper end
         } finally {
             try {
-                net.minecrell.terminalconsole.TerminalConsoleAppender.close(); // Paper - Use TerminalConsoleAppender
+                //net.minecrell.terminalconsole.TerminalConsoleAppender.close(); // Paper - Move into stop
             } catch (Exception e) {
             }
         }
diff --git a/src/main/java/org/spigotmc/RestartCommand.java b/src/main/java/org/spigotmc/RestartCommand.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/spigotmc/RestartCommand.java
+++ b/src/main/java/org/spigotmc/RestartCommand.java
@@ -0,0 +0,0 @@ public class RestartCommand extends Command
     // Paper end
 
     // Paper start - copied from above and modified to return if the hook registered
-    private static boolean addShutdownHook(String restartScript)
+    public static boolean addShutdownHook(String restartScript)
     {
         String[] split = restartScript.split( " " );
         if ( split.length > 0 && new File( split[0] ).isFile() )
diff --git a/src/main/java/org/spigotmc/WatchdogThread.java b/src/main/java/org/spigotmc/WatchdogThread.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/spigotmc/WatchdogThread.java
+++ b/src/main/java/org/spigotmc/WatchdogThread.java
@@ -0,0 +0,0 @@ import org.bukkit.Bukkit;
 public class WatchdogThread extends Thread
 {
 
+    public static final boolean DISABLE_WATCHDOG = Boolean.getBoolean("disable.watchdog"); // Paper
     private static WatchdogThread instance;
     private long timeoutTime;
     private boolean restart;
@@ -0,0 +0,0 @@ public class WatchdogThread extends Thread
     {
         if ( WatchdogThread.instance == null )
         {
+            if (timeoutTime <= 0) timeoutTime = 300; // Paper
             WatchdogThread.instance = new WatchdogThread( timeoutTime * 1000L, restart );
             WatchdogThread.instance.start();
         } else
@@ -0,0 +0,0 @@ public class WatchdogThread extends Thread
             // Paper start
             Logger log = Bukkit.getServer().getLogger();
             long currentTime = WatchdogThread.monotonicMillis();
-            if ( this.lastTick != 0 && this.timeoutTime > 0 && currentTime > this.lastTick + this.earlyWarningEvery && !Boolean.getBoolean("disable.watchdog")) // Paper - Add property to disable
+            MinecraftServer server = MinecraftServer.getServer();
+            if ( this.lastTick != 0 && this.timeoutTime > 0 && WatchdogThread.hasStarted && (!server.isRunning() || (currentTime > this.lastTick + this.earlyWarningEvery && !DISABLE_WATCHDOG) )) // Paper - add property to disable
             {
-                boolean isLongTimeout = currentTime > lastTick + timeoutTime;
+                boolean isLongTimeout = currentTime > lastTick + timeoutTime || (!server.isRunning() && !server.hasStopped() && currentTime > lastTick + 1000);
                 // Don't spam early warning dumps
                 if ( !isLongTimeout && (earlyWarningEvery <= 0 || !hasStarted || currentTime < lastEarlyWarning + earlyWarningEvery || currentTime < lastTick + earlyWarningDelay)) continue;
-                if ( !isLongTimeout && MinecraftServer.getServer().hasStopped()) continue; // Don't spam early watchdog warnings during shutdown, we'll come back to this...
+                if ( !isLongTimeout && server.hasStopped()) continue; // Don't spam early watchdog warnings during shutdown, we'll come back to this...
                 lastEarlyWarning = currentTime;
                 if (isLongTimeout) {
                 // Paper end
@@ -0,0 +0,0 @@ public class WatchdogThread extends Thread
                 log.log( Level.SEVERE, "------------------------------" );
                 log.log( Level.SEVERE, "Server thread dump (Look for plugins here before reporting to Paper!):" ); // Paper
                 com.destroystokyo.paper.io.chunk.ChunkTaskManager.dumpAllChunkLoadInfo(); // Paper
-                WatchdogThread.dumpThread( ManagementFactory.getThreadMXBean().getThreadInfo( MinecraftServer.getServer().serverThread.getId(), Integer.MAX_VALUE ), log );
+                WatchdogThread.dumpThread( ManagementFactory.getThreadMXBean().getThreadInfo( server.serverThread.getId(), Integer.MAX_VALUE ), log );
                 log.log( Level.SEVERE, "------------------------------" );
                 //
                 // Paper start - Only print full dump on long timeouts
@@ -0,0 +0,0 @@ public class WatchdogThread extends Thread
 
                 if ( isLongTimeout )
                 {
-                if ( this.restart && !MinecraftServer.getServer().hasStopped() )
+                if ( !server.hasStopped() )
                 {
-                    RestartCommand.restart();
+                    AsyncCatcher.enabled = false; // Disable async catcher incase it interferes with us
+                    AsyncCatcher.shuttingDown = true;
+                    server.forceTicks = true;
+                    if (restart) {
+                        RestartCommand.addShutdownHook( SpigotConfig.restartScript );
+                    }
+                    // try one last chance to safe shutdown on main incase it 'comes back'
+                    server.abnormalExit = true;
+                    server.safeShutdown(false, restart);
+                    try {
+                        Thread.sleep(1000);
+                    } catch (InterruptedException e) {
+                        e.printStackTrace();
+                    }
+                    if (!server.hasStopped()) {
+                        server.close();
+                    }
                 }
                 break;
                 } // Paper end
diff --git a/src/main/resources/log4j2.xml b/src/main/resources/log4j2.xml
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/resources/log4j2.xml
+++ b/src/main/resources/log4j2.xml
@@ -0,0 +0,0 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<Configuration status="WARN" packages="com.mojang.util">
+<Configuration status="WARN" packages="com.mojang.util" shutdownHook="disable">
     <Appenders>
         <Queue name="ServerGuiConsole">
             <PatternLayout pattern="[%d{HH:mm:ss} %level]: %msg%n" />