package webapp;

import java.lang.management.*;

import java.util.logging.Logger;

public class DeadLockDetector implements Runnable {

private static final Logger log = Logger.getLogger(DeadLockDetector.class.getName());

private static DeadLockDetector instance;

private final ThreadMXBean tmx;

public static DeadLockDetector getInstance() {

return instance;

}

private DeadLockDetector() {

tmx = ManagementFactory.getThreadMXBean();

instance = this;

}

public final void run() {

boolean deadlock = false;

while (!deadlock) {

try {

long[] ids = tmx.findDeadlockedThreads();

// Deadlock detected

if (ids != null) {

deadlock = true;

ThreadInfo[] tis = tmx.getThreadInfo(ids, true, true);

String info = "DeadLock Found!\n";

for (ThreadInfo ti : tis) {

info += ti.toString();

}

for (ThreadInfo ti : tis) {

LockInfo[] locks = ti.getLockedSynchronizers();

MonitorInfo[] monitors = ti.getLockedMonitors();

if (locks.length == 0 && monitors.length == 0) {

// This thread isn't a reason, it's just blocked by external deadlock

continue;

}

ThreadInfo dl = ti;

info += "Java-level deadlock:\n";

info += "\t" + dl.getThreadName() + " is waiting to lock " + dl.getLockInfo().toString() + " which is held by " + dl.getLockOwnerName() + "\n";

while ((dl = tmx.getThreadInfo(new long[]{dl.getLockOwnerId()}, true, true)[0]).getThreadId() != ti.getThreadId()) {

info += "\t" + dl.getThreadName() + " is waiting to lock " + dl.getLockInfo().toString() + " which is held by " + dl.getLockOwnerName() + "\n";

}

}

log.severe(info);

log.severe("Shutting down server with exit code = 2, startup script will do authomatic restart.");

System.exit(2);

}

Thread.sleep(200);

}

catch (Exception e) {

log.severe(e.getLocalizedMessage());

}

}

}

public static void DeadLockDetectorStart() {

Thread t = new Thread(new DeadLockDetector());

t.setName("DeadLock Monitor");

t.setDaemon(true);

t.setPriority(Thread.MAX_PRIORITY);

t.start();

log.info("DeadLock Detector started.");

}

}