DeadLockDetector.java

package me.nallar.tickthreading.minecraft;

import java.lang.management.LockInfo;
import java.lang.management.ManagementFactory;
import java.lang.management.MonitorInfo;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import java.util.EnumSet;
import java.util.Map;
import java.util.TreeMap;

import cpw.mods.fml.common.FMLCommonHandler;
import cpw.mods.fml.common.ITickHandler;
import cpw.mods.fml.common.TickType;
import cpw.mods.fml.common.registry.TickRegistry;
import cpw.mods.fml.relauncher.Side;
import javassist.is.faulty.Timings;
import me.nallar.tickthreading.Log;
import net.minecraft.network.packet.Packet3Chat;
import net.minecraft.server.MinecraftServer;

public class DeadLockDetector {
	private boolean sentWarningRecently = false;
	private static volatile String lastJob = "";
	private static volatile long lastTickTime = 0;
	private static final ITickHandler tickHandler = new ITickHandler() {
		private final EnumSet<TickType> tickTypes = EnumSet.of(TickType.SERVER, TickType.CLIENTGUI);

		@Override
		public void tickStart(EnumSet<TickType> type, Object... tickData) {
			tick("Server tick start");
			if (type.contains(TickType.SERVER)) {
				Timings.tick();
			}
		}

		@Override
		public void tickEnd(EnumSet<TickType> type, Object... tickData) {
		}

		@Override
		public EnumSet<TickType> ticks() {
			return tickTypes;
		}

		@Override
		public String getLabel() {
			return "TickThreading Deadlock Detector";
		}
	};

	public DeadLockDetector() {
		Thread deadlockThread = new Thread(new Runnable() {
			@Override
			public void run() {
				while (checkForDeadlocks()) {
					try {
						Thread.sleep(6000);
					} catch (InterruptedException ignored) {
					}
				}
			}
		});
		deadlockThread.setDaemon(true);
		deadlockThread.setName("Deadlock Detector");
		deadlockThread.start();
		TickRegistry.registerTickHandler(tickHandler, Side.SERVER);
		TickRegistry.registerTickHandler(tickHandler, Side.CLIENT);
	}

	public static synchronized long tick(String name) {
		lastJob = name;
		return lastTickTime = System.currentTimeMillis();
	}

	public static void sendChatSafely(final String message) {
		// This might freeze, if the deadlock was related to the playerlist, so do it in another thread.
		new Thread() {
			@Override
			public void run() {
				MinecraftServer.getServerConfigurationManager(MinecraftServer.getServer())
						.sendPacketToAllPlayers(new Packet3Chat(message));
			}
		}.start();
	}

	public boolean checkForDeadlocks() {
		Log.flush();
		int deadTime = (int) (System.currentTimeMillis() - lastTickTime);
		if (lastTickTime == 0 || (!MinecraftServer.getServer().isServerRunning() && deadTime < (TickThreading.instance.deadLockTime * 10000))) {
			return true;
		}
		if (TickThreading.instance.exitOnDeadlock) {
			if (sentWarningRecently && deadTime < 10000) {
				sentWarningRecently = false;
				sendChatSafely("The server has recovered and will not need to restart. :)");
			} else if (deadTime > 10000) {
				sendChatSafely("The server appears to have frozen and will restart soon if it does not recover. :(");
			}
		}
		if (deadTime < (TickThreading.instance.deadLockTime * 1000)) {
			return true;
		}
		if (TickThreading.instance.exitOnDeadlock) {
			sendChatSafely("The server is restarting - be right back!");
		}
		TreeMap<String, Thread> sortedThreads = new TreeMap<String, Thread>();
		StringBuilder sb = new StringBuilder();
		ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
		sb.append("The server appears to have deadlocked.")
				.append("\nLast tick ").append(deadTime).append("ms ago.")
				.append("\nTicking: ").append(lastJob).append('\n');
		Map<Thread, StackTraceElement[]> traces = Thread.getAllStackTraces();
		for (Thread thread : traces.keySet()) {
			sortedThreads.put(thread.getName(), thread);
		}
		for (Thread thread : sortedThreads.values()) {
			sb.append("Current Thread: ").append(thread.getName()).append('\n').append("    PID: ").append(thread.getId())
					.append(" | Alive: ").append(thread.isAlive()).append(" | State: ").append(thread.getState())
					.append(" | Daemon: ").append(thread.isDaemon()).append(" | Priority:").append(thread.getPriority())
					.append('\n');
			sb.append("    ").append(toString(threadMXBean.getThreadInfo(thread.getId(), Integer.MAX_VALUE), false)).append('\n');
		}
		long[] deadlockedThreads = threadMXBean.findDeadlockedThreads();

		if (deadlockedThreads != null) {
			ThreadInfo[] infos = threadMXBean.getThreadInfo(deadlockedThreads, true, true);
			sb.append("Definitely deadlocked: \n");
			for (ThreadInfo threadInfo : infos) {
				sb.append(toString(threadInfo, true)).append('\n');
			}
		}
		Log.severe(sb.toString());
		Log.flush();
		// Yes, we save multiple times - handleServerStopping may freeze on the same thing we deadlocked on, but if it doesn't might change stuff
		// which needs to be saved.
		MinecraftServer minecraftServer = MinecraftServer.getServer();
		if (minecraftServer.currentlySaving) {
			Log.severe("World state is possibly corrupted! Sleeping for 2 minutes - will force save after.");
			Log.flush();
			minecraftServer.currentlySaving = false;
			try {
				Thread.sleep(1000 * 120);
			} catch (InterruptedException ignored) {
			}
		}
		Log.info("Attempting to save");
		Log.flush();
		minecraftServer.saveEverything(); // Save first
		new Thread() {
			@Override
			public void run() {
				try {
					Thread.sleep(300000);
				} catch (InterruptedException ignored) {
				}
				Log.severe("Froze while attempting to stop - halting server.");
				Log.flush();
				Runtime.getRuntime().halt(1);
			}
		}.start();
		Log.info("Attempting to stop mods and disconnect players cleanly");
		try {
			minecraftServer.stopServer();
			FMLCommonHandler.instance().handleServerStopping(); // Try to get mods to save data - this may lock up, as we deadlocked.
		} catch (Exception e) {
			Log.severe("Error stopping server", e);
		}
		minecraftServer.saveEverything(); // Save again, in case they changed anything.
		minecraftServer.initiateShutdown();
		Log.flush();
		if (TickThreading.instance.exitOnDeadlock) {
			try {
				Thread.sleep(5000);
			} catch (InterruptedException ignored) {
			}
			Runtime.getRuntime().exit(1);
		}
		return false;
	}

	private static String toString(ThreadInfo threadInfo, boolean name) {
		if (threadInfo == null) {
			return "";
		}
		StringBuilder sb = new StringBuilder();
		if (name) {
			sb.append('"').append(threadInfo.getThreadName()).append('"').append(" Id=").append(threadInfo.getThreadId())
					.append(' ');
		}
		sb.append(threadInfo.getThreadState());
		if (threadInfo.getLockName() != null) {
			sb.append(" on ").append(threadInfo.getLockName());
		}
		if (threadInfo.getLockOwnerName() != null) {
			sb.append(" owned by \"").append(threadInfo.getLockOwnerName()).append("\" Id=").append(threadInfo.getLockOwnerId());
		}
		if (threadInfo.isSuspended()) {
			sb.append(" (suspended)");
		}
		if (threadInfo.isInNative()) {
			sb.append(" (in native)");
		}
		sb.append('\n');
		int i = 0;
		StackTraceElement[] stackTrace = threadInfo.getStackTrace();
		for (; i < stackTrace.length; i++) {
			StackTraceElement ste = stackTrace[i];
			sb.append("\tat ").append(ste.toString());
			sb.append('\n');
			if (i == 0 && threadInfo.getLockInfo() != null) {
				Thread.State ts = threadInfo.getThreadState();
				switch (ts) {
					case BLOCKED:
						sb.append("\t-  blocked on ").append(threadInfo.getLockInfo());
						sb.append('\n');
						break;
					case WAITING:
						sb.append("\t-  waiting on ").append(threadInfo.getLockInfo());
						sb.append('\n');
						break;
					case TIMED_WAITING:
						sb.append("\t-  waiting on ").append(threadInfo.getLockInfo());
						sb.append('\n');
						break;
					default:
				}
			}

			for (MonitorInfo mi : threadInfo.getLockedMonitors()) {
				if (mi.getLockedStackDepth() == i) {
					sb.append("\t-  locked ").append(mi);
					sb.append('\n');
				}
			}
		}
		if (i < stackTrace.length) {
			sb.append("\t...");
			sb.append('\n');
		}

		LockInfo[] locks = threadInfo.getLockedSynchronizers();
		if (locks.length > 0) {
			sb.append("\n\tNumber of locked synchronizers = ").append(locks.length);
			sb.append('\n');
			for (LockInfo li : locks) {
				sb.append("\t- ").append(li);
				sb.append('\n');
			}
		}
		sb.append('\n');
		return sb.toString();
	}
}