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] 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.

diff --git a/src/main/java/net/minecraft/server/CrashReport.java b/src/main/java/net/minecraft/server/CrashReport.java
index 3de19c998b749ccf74958c2412a8c9506457383e..c7dc8787cc3456c5540d6a00a6ff051533edc25a 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 1ef7890da599d13e784861035e7891efcc4cd504..e62ca0543f1819259ad8720ad792fed3ef134d6a 100644
--- a/src/main/java/net/minecraft/server/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/DedicatedServer.java
@@ -750,7 +750,7 @@ public class DedicatedServer extends MinecraftServer implements IMinecraftServer
     @Override
     public void stop() {
         super.stop();
-        SystemUtils.f();
+        //SystemUtils.f(); // 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 cfe43e882e524b6ab3d9702e81269c97e6b75eba..2632c7c3ec77918be7979f2aa49209e566cafc77 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.bi(), exception);
         }
 
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 5f57a9e1c8d5f641facdadbd1877637a8fe8daf5..98f03983485058a5e9ad9c3f81a9cfc2df36e304 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -144,6 +144,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
     private final ResourcePackRepository<ResourcePackLoader> resourcePackRepository;
     @Nullable
     private ResourcePackSourceFolder resourcePackFolder;
+    public volatile Thread shutdownThread; // Paper
     public CommandDispatcher commandDispatcher;
     private final CraftingManager craftingManager;
     private final TagRegistry tagRegistry;
@@ -176,7 +177,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
     public boolean serverAutoSave = false; // Paper
     public File bukkitDataPackFolder;
     public CommandDispatcher vanillaCommandDispatcher;
-    private boolean forceTicks;
+    public boolean forceTicks; // Paper
     // CraftBukkit end
     // Spigot start
     public static final int TPS = 20;
@@ -725,7 +726,12 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
         // CraftBukkit start - prevent double stopping on multiple threads
         synchronized(stopLock) {
             if (hasStopped) return;
+            shutdownThread = Thread.currentThread();
             hasStopped = true;
+            org.spigotmc.WatchdogThread.doStop(); // Paper
+            if (!isMainThread()) {
+                this.getThread().stop();
+            }
         }
         // CraftBukkit end
         MinecraftServer.LOGGER.info("Stopping server");
@@ -782,7 +788,18 @@ 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() {
@@ -882,6 +899,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
                 this.a(this.serverPing);
 
                 // Spigot start
+                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
@@ -938,6 +956,12 @@ 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 )
@@ -969,14 +993,14 @@ 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
             }
 
         }
@@ -1032,6 +1056,12 @@ 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);
     }
 
diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
index 0b5800649abfc2fd6722e4cb5e8e40e51240a032..62891d2dc6f40bb57e92dfefcbcdf72f89ba5c4f 100644
--- a/src/main/java/net/minecraft/server/PlayerList.java
+++ b/src/main/java/net/minecraft/server/PlayerList.java
@@ -400,7 +400,7 @@ 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 dc6d030621b66e43edf3a148f0eca43382383705..bc8b9046605657e0be5858ae9cf14d7793256983 100644
--- a/src/main/java/net/minecraft/server/SystemUtils.java
+++ b/src/main/java/net/minecraft/server/SystemUtils.java
@@ -109,6 +109,7 @@ public class SystemUtils {
         return SystemUtils.c;
     }
 
+    public static void shutdownServerThreadPool() { f(); } // Paper - OBFHELPER
     public static void f() {
         SystemUtils.c.shutdown();
 
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index de9f49b884838105c537b73d69234eb26fddb708..c8619af2cf43041e3eebec74e24c7f127a662efe 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -792,6 +792,7 @@ 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);
@@ -867,6 +868,7 @@ 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 b627180729a24a83ca383f83aee53133ea1b398e..f49193d9d7cd9655fdedf64bebdcf4e1a9b77f2c 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -1706,7 +1706,7 @@ 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/util/ServerShutdownThread.java b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
index 449e99d1b673870ed6892f6ab2c715a2db35c35d..899a525209cfe047ce57e758c6328a130f916dc6 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
@@ -12,12 +12,25 @@ 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()) {
+                return;
+            }
+            // Looks stalled, close async
             org.spigotmc.AsyncCatcher.enabled = false; // Spigot
             org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper
+            server.forceTicks = true;
             server.close();
+        } 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..fe4b8caf28b2d36b2034ac90b1a76dea7b691feb 100644
--- a/src/main/java/org/spigotmc/WatchdogThread.java
+++ b/src/main/java/org/spigotmc/WatchdogThread.java
@@ -41,6 +41,7 @@ public class WatchdogThread extends Thread
     {
         if ( instance == null )
         {
+            if (timeoutTime <= 0) timeoutTime = 300; // Paper
             instance = new WatchdogThread( timeoutTime * 1000L, restart );
             instance.start();
         }
@@ -67,12 +68,13 @@ 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 && !Boolean.getBoolean("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 +116,7 @@ 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 +137,24 @@ 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