papermc/Spigot-Server-Patches/0447-Improved-Watchdog-Support.patch

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 f2a0a9f5d86820ce8098301256d2faf3d1a7c697..8a19c96499c22f0d4705613ffec38d5677e1a72d 100644
--- a/src/main/java/com/destroystokyo/paper/Metrics.java
+++ b/src/main/java/com/destroystokyo/paper/Metrics.java
@@ -86,6 +86,9 @@ public class Metrics {
         timer.scheduleAtFixedRate(new TimerTask() {
             @Override
             public void run() {
+                if (MinecraftServer.getServer().hasStopped()) {
+                    return;
+                }
                 submitData();
             }
         }, 1000 * 60 * 5, 1000 * 60 * 30);
diff --git a/src/main/java/net/minecraft/server/CrashReport.java b/src/main/java/net/minecraft/server/CrashReport.java
index 95e6a6de7ccfc4445d0ac19c5f874c0d533b1712..cc6e6f245ee5e73bd570cf42381bf55ee0b364d3 100644
--- a/src/main/java/net/minecraft/server/CrashReport.java
+++ b/src/main/java/net/minecraft/server/CrashReport.java
@@ -257,6 +257,7 @@ public class CrashReport {
     }
 
     public static CrashReport a(Throwable throwable, String s) {
+        if (throwable instanceof ThreadDeath) com.destroystokyo.paper.util.SneakyThrow.sneaky(throwable); // Paper
         while (throwable instanceof CompletionException && throwable.getCause() != null) {
             throwable = throwable.getCause();
         }
diff --git a/src/main/java/net/minecraft/server/DedicatedServer.java b/src/main/java/net/minecraft/server/DedicatedServer.java
index 87753a94792af94454f76a2beb1ab9f1027f514f..4c561181a977fd0244325880bb6a8cd6a54dcacc 100644
--- a/src/main/java/net/minecraft/server/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/DedicatedServer.java
@@ -242,7 +242,7 @@ public class DedicatedServer extends MinecraftServer implements IMinecraftServer
             long j = SystemUtils.getMonotonicNanos() - 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.GameRuleBoolean) this.getGameRules().get(GameRules.ANNOUNCE_ADVANCEMENTS)).a(dedicatedserverproperties.announcePlayerAchievements, (MinecraftServer) this);
             }
@@ -368,6 +368,7 @@ public class DedicatedServer extends MinecraftServer implements IMinecraftServer
             //this.remoteStatusListener.b(); // Paper - don't wait for remote connections
         }
 
+        hasFullyShutdown = true; // Paper
         System.exit(0); // CraftBukkit
     }
 
@@ -696,7 +697,7 @@ public class DedicatedServer extends MinecraftServer implements IMinecraftServer
     @Override
     public void stop() {
         super.stop();
-        SystemUtils.h();
+        //SystemUtils.h(); // Paper - moved into super
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/server/IAsyncTaskHandler.java b/src/main/java/net/minecraft/server/IAsyncTaskHandler.java
index 63fdae15ccbef0c39718b320dbd096794bcfa3b4..6beefff203ed6e448898eb5b2e95800def868381 100644
--- a/src/main/java/net/minecraft/server/IAsyncTaskHandler.java
+++ b/src/main/java/net/minecraft/server/IAsyncTaskHandler.java
@@ -135,6 +135,7 @@ public abstract class IAsyncTaskHandler<R extends Runnable> implements Mailbox<R
         try {
             r0.run();
         } catch (Exception exception) {
+            if (exception.getCause() instanceof ThreadDeath) throw exception; // Paper
             IAsyncTaskHandler.LOGGER.fatal("Error executing task on {}", this.bh(), exception);
         }
 
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 04eb2af28f9843ef7641f5464d2a043c696de864..fb65978d783a91b341658e0ebe393ab77153a0d9 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -159,7 +159,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
     public int autosavePeriod;
     public boolean serverAutoSave = false; // Paper
     public CommandDispatcher vanillaCommandDispatcher;
-    private boolean forceTicks;
+    public boolean forceTicks; // Paper
     // CraftBukkit end
     // Spigot start
     public static final int TPS = 20;
@@ -169,6 +169,8 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
     public final SlackActivityAccountant slackActivityAccountant = new SlackActivityAccountant();
     // Spigot end
 
+    public volatile Thread shutdownThread; // Paper
+
     public static <S extends MinecraftServer> S a(Function<Thread, S> function) {
         AtomicReference<S> atomicreference = new AtomicReference();
         Thread thread = new Thread(() -> {
@@ -737,6 +739,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
 
     // CraftBukkit start
     private boolean hasStopped = false;
+    public volatile boolean hasFullyShutdown = false; // Paper
     private final Object stopLock = new Object();
     public final boolean hasStopped() {
         synchronized (stopLock) {
@@ -751,6 +754,19 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
             if (hasStopped) return;
             hasStopped = true;
         }
+        // Paper start - kill main thread, and kill it hard
+        shutdownThread = Thread.currentThread();
+        org.spigotmc.WatchdogThread.doStop(); // Paper
+        if (!isMainThread()) {
+            MinecraftServer.LOGGER.info("Stopping main thread (Ignore any thread death message you see! - DO NOT REPORT THREAD DEATH TO PAPER)");
+            while (this.getThread().isAlive()) {
+                this.getThread().stop();
+                try {
+                    Thread.sleep(1);
+                } catch (InterruptedException e) {}
+            }
+        }
+        // Paper end
         // CraftBukkit end
         MinecraftServer.LOGGER.info("Stopping server");
         MinecraftTimings.stopServer(); // Paper
@@ -816,7 +832,18 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
             this.getUserCache().c(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");
+        SystemUtils.shutdownServerThreadPool(); // Paper
+        LOGGER.info("Closing Server");
+        try {
+            net.minecrell.terminalconsole.TerminalConsoleAppender.close(); // Paper - Use TerminalConsoleAppender
+        } catch (Exception e) {
+        }
+        this.exit();
+        // Paper end
     }
 
     public String getServerIp() {
@@ -909,6 +936,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
 
     protected void v() {
         try {
+            long serverStartTime = SystemUtils.getMonotonicNanos(); // Paper
             if (this.init()) {
                 this.nextTick = SystemUtils.getMonotonicMillis();
                 this.serverPing.setMOTD(new ChatComponentText(this.motd));
@@ -916,6 +944,18 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
                 this.a(this.serverPing);
 
                 // Spigot start
+                // Paper start - move done tracking
+                LOGGER.info("Running delayed init tasks");
+                this.server.getScheduler().mainThreadHeartbeat(this.ticks); // 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) (SystemUtils.getMonotonicNanos() - 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
@@ -971,6 +1011,12 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
                 this.a((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 )
@@ -1002,14 +1048,14 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
             } 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.exit();
+                //this.exit(); // Paper - moved into stop
             }
 
         }
@@ -1065,6 +1111,12 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
 
     @Override
     protected TickTask postToMainThread(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.ticks, runnable);
     }
 
@@ -1307,6 +1359,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
                 try {
                     crashreport = CrashReport.a(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
@@ -1757,7 +1810,8 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
             this.resourcePackRepository.a(collection);
             this.saveData.a(a(this.resourcePackRepository));
             datapackresources.i();
-            this.getPlayerList().savePlayers();
+            if (Thread.currentThread() != this.serverThread) return; // Paper
+            //this.getPlayerList().savePlayers(); // Paper - we don't need to do this
             this.getPlayerList().reload();
             this.customFunctionData.a(this.dataPackResources.a());
             this.ak.a(this.dataPackResources.h());
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index d95ef14f5a4babc8c8fff349baf6a9aa44edcc82..1fcf75b2ed3c8c1ca2e31f679fc7d507f963caf2 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -486,6 +486,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
             MutableBoolean mutableboolean = new MutableBoolean();
 
             do {
+                boolean isShuttingDown = world.getMinecraftServer().hasStopped(); // Paper
                 mutableboolean.setFalse();
                 list.stream().map((playerchunk) -> {
                     CompletableFuture completablefuture;
diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
index 4676b4dc4b22c838c946a342af9e88b56436de70..db049d529c4ed9157a1136695e5cd14429fd442f 100644
--- a/src/main/java/net/minecraft/server/PlayerList.java
+++ b/src/main/java/net/minecraft/server/PlayerList.java
@@ -429,7 +429,7 @@ public abstract class PlayerList {
         cserver.getPluginManager().callEvent(playerQuitEvent);
         entityplayer.getBukkitEntity().disconnect(playerQuitEvent.getQuitMessage());
 
-        entityplayer.playerTick(); // SPIGOT-924
+        if (server.isMainThread()) entityplayer.playerTick(); // 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/server/SystemUtils.java b/src/main/java/net/minecraft/server/SystemUtils.java
index 5579044782f155f587de1e2ea5115bde6053f722..e8075ad6b5395c7dce12741fe85dafd13f72cf41 100644
--- a/src/main/java/net/minecraft/server/SystemUtils.java
+++ b/src/main/java/net/minecraft/server/SystemUtils.java
@@ -119,6 +119,7 @@ public class SystemUtils {
         return SystemUtils.f;
     }
 
+    public static void shutdownServerThreadPool() { h(); } // Paper - OBFHELPER
     public static void h() {
         a(SystemUtils.e);
         a(SystemUtils.f);
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index a31d293a00d325e4ee1eba48126b112df117fcfc..bcfa630ae8d7a1454ea2f8e6e88b8902cb586467 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -846,6 +846,7 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
 
                         gameprofilerfiller.exit();
                     } catch (Throwable throwable) {
+                        if (throwable instanceof ThreadDeath) throw throwable; // Paper
                         // Paper start - Prevent tile entity and entity crashes
                         String msg = "TileEntity threw exception at " + tileentity.world.getWorld().getName() + ":" + tileentity.position.getX() + "," + tileentity.position.getY() + "," + tileentity.position.getZ();
                         System.err.println(msg);
@@ -921,6 +922,7 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
         try {
             consumer.accept(entity);
         } catch (Throwable throwable) {
+            if (throwable instanceof ThreadDeath) throw throwable; // Paper
             // Paper start - Prevent tile entity and entity crashes
             String msg = "Entity threw exception at " + entity.world.getWorld().getName() + ":" + entity.locX() + "," + entity.locY() + "," + entity.locZ();
             System.err.println(msg);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index 9111bc559353bc09eaf9a05a35b2d921f54b9f10..c80fd400cd6eb2c31890ebce55844da36a84c7d0 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1792,7 +1792,7 @@ 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
     }
 
     @Override
diff --git a/src/main/java/org/bukkit/craftbukkit/Main.java b/src/main/java/org/bukkit/craftbukkit/Main.java
index 2049f9783bf93c56d8c4dcb395293c03f09b5b40..ac8f1681d91251ff84938f94fc59db97560000d6 100644
--- a/src/main/java/org/bukkit/craftbukkit/Main.java
+++ b/src/main/java/org/bukkit/craftbukkit/Main.java
@@ -150,6 +150,37 @@ public class Main {
 
         OptionSet options = null;
 
+        // Paper start - preload logger classes to avoid plugins mixing versions
+        tryPreloadClass("com.destroystokyo.paper.log.LogFullPolicy");
+        tryPreloadClass("org.apache.logging.log4j.core.Core");
+        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.ThrowableProxy$CacheEntry");
+        tryPreloadClass("org.apache.logging.log4j.core.impl.ExtendedClassInfo");
+        tryPreloadClass("org.apache.logging.log4j.core.impl.ExtendedStackTraceElement");
+        // Paper end
         try {
             options = parser.parse(args);
         } catch (joptsimple.OptionException ex) {
@@ -245,8 +276,63 @@ public class Main {
             } catch (Throwable t) {
                 t.printStackTrace();
             }
+            // Paper start
+            // load some required classes to avoid errors during shutdown if jar is replaced
+            // also to guarantee our version loads over plugins
+            tryPreloadClass("com.destroystokyo.paper.util.SneakyThrow");
+            tryPreloadClass("com.google.common.collect.Iterators$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$11");
+            tryPreloadClass("io.netty.channel.AbstractChannel$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$4");
+            tryPreloadClass("org.slf4j.helpers.MessageFormatter");
+            tryPreloadClass("org.slf4j.helpers.FormattingTuple");
+            tryPreloadClass("org.slf4j.helpers.BasicMarker");
+            tryPreloadClass("org.slf4j.helpers.Util");
+            tryPreloadClass("com.destroystokyo.paper.event.player.PlayerConnectionCloseEvent");
+            tryPreloadClass("com.destroystokyo.paper.event.entity.EntityRemoveFromWorldEvent");
+            // Minecraft, seen during saving
+            tryPreloadClass("net.minecraft.server.LightEngineLayerEventListener$Void");
+            tryPreloadClass("net.minecraft.server.LightEngineLayerEventListener");
+            tryPreloadClass("net.minecraft.server.ExceptionSuppressor");
+            // 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 449e99d1b673870ed6892f6ab2c715a2db35c35d..c7ed6e0f8a989cec97700df2b15198c9c481c549 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
@@ -12,12 +12,27 @@ 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;
             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 aefea3a9a8b9b75c62bd20018be7cd166a213001..123de5ac9026508e21cdc225f0962f5c3c46fed5 100644
--- a/src/main/java/org/spigotmc/RestartCommand.java
+++ b/src/main/java/org/spigotmc/RestartCommand.java
@@ -139,7 +139,7 @@ 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 5bdcdcf9e85b73086722783bff26321d03382bb9..513c1041c34ebb3ac1775674a3f4526693759c08 100644
--- a/src/main/java/org/spigotmc/WatchdogThread.java
+++ b/src/main/java/org/spigotmc/WatchdogThread.java
@@ -13,6 +13,7 @@ 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 final long timeoutTime;
     private final long earlyWarningEvery; // Paper - Timeout time for just printing a dump but not restarting
@@ -41,6 +42,7 @@ public class WatchdogThread extends Thread
     {
         if ( instance == null )
         {
+            if (timeoutTime <= 0) timeoutTime = 300; // Paper
             instance = new WatchdogThread( timeoutTime * 1000L, restart );
             instance.start();
         }
@@ -67,12 +69,13 @@ public class WatchdogThread extends Thread
             // Paper start
             Logger log = Bukkit.getServer().getLogger();
             long currentTime = monotonicMillis();
-            if ( lastTick != 0 && currentTime > lastTick + earlyWarningEvery && !Boolean.getBoolean("disable.watchdog") )
+            MinecraftServer server = MinecraftServer.getServer();
+            if (lastTick != 0 && hasStarted && (!server.isRunning() || (currentTime > lastTick + earlyWarningEvery && !DISABLE_WATCHDOG) ))
             {
-                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
@@ -114,7 +117,7 @@ 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
                 ChunkTaskManager.dumpAllChunkLoadInfo(); // Paper
-                dumpThread( ManagementFactory.getThreadMXBean().getThreadInfo( MinecraftServer.getServer().serverThread.getId(), Integer.MAX_VALUE ), log );
+                dumpThread( ManagementFactory.getThreadMXBean().getThreadInfo( server.serverThread.getId(), Integer.MAX_VALUE ), log );
                 log.log( Level.SEVERE, "------------------------------" );
                 //
                 // Paper start - Only print full dump on long timeouts
@@ -135,9 +138,24 @@ public class WatchdogThread extends Thread
 
                 if ( isLongTimeout )
                 {
-                if ( 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.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 476f4a5cbe664ddd05474cb88553018bd334a5b8..8af159abd3d0cc94cf155fec5b384c42f69551bf 100644
--- a/src/main/resources/log4j2.xml
+++ b/src/main/resources/log4j2.xml
@@ -1,5 +1,5 @@
 <?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" />