An example of using JMX from Jython. In particular, running kill_deadlocked_jvms.py will kill any deadlocked JVM process. To cause a deadlock, simply run deadlock.py with Jython. Although deadlock.py is portable Python, running with Jython does allow for the deadlock detection supported by the JVM. Examples are from my 2012 OSCON talk.

deadlock.py

from threading import Thread, Lock
import threading


def cause_deadlock():
    lock_one = Lock()
    lock_two = Lock()
    counter = [0]  # Shared resource for both locks
    Thread(name="thread #1", target=acquire_locks,
           args=(counter, lock_one, lock_two)).start()
    Thread(name="thread #2 (reversed)", target=acquire_locks,
           args=(counter, lock_two, lock_one)).start()


def acquire_locks(counter, lock1, lock2):
    # Will eventually deadlock if locks are acquired in different order
    name = threading.currentThread().getName()
    thread_count = 0
    while True:
        with lock1:
            with lock2:
                counter[0] += 1
                thread_count += 1
                print "name={}, total count={}, thread count={}".\
                    format(name, counter[0], thread_count)


if __name__ == '__main__':
    cause_deadlock()

kill_deadlocked_jvms.py

import os.path
import signal
from contextlib import closing

from com.sun.tools.attach import VirtualMachine
from java.lang import Class
from java.lang.management import ManagementFactory
from javax.management.remote import JMXServiceURL, JMXConnectorFactory


def get_vm_connectors(exclude_self=True):
    my_pid = os.getpid()
    for desc in VirtualMachine.list():
        vm = VirtualMachine.attach(desc)
        pid = int(desc.id())
        if exclude_self and pid == my_pid:
            continue
        connector_addr = vm.agentProperties["com.sun.management.jmxremote.localConnectorAddress"]
        if connector_addr is None:
            # Need to load a JMX agent into the JVM
            system_props = vm.systemProperties
            agent = os.path.join(
                system_props["java.home"], "lib", "management-agent.jar")
            print "Loading management agent={} for pid={}...".format(agent, pid)
            vm.loadAgent(agent)
            connector_addr = vm.agentProperties["com.sun.management.jmxremote.localConnectorAddress"]
        yield pid, connector_addr


def check_and_kill_deadlocked_vm(pid, connector_addr):
    url = JMXServiceURL(connector_addr)
    print "Checking vm pid={}, url={}".format(pid, url)
    with closing(JMXConnectorFactory.connect(url)) as connector:
        mbean = connector.MBeanServerConnection
        thread_mxbean = ManagementFactory.getPlatformMXBean(
            mbean, Class.forName("java.lang.management.ThreadMXBean"))
        thread_ids = thread_mxbean.findDeadlockedThreads()
        if thread_ids:
            print "Deadlock detected, shutting down pid={}, threads={}".\
                format(pid, list(thread_ids))
            os.kill(pid, signal.SIGINT)


def main():
    for pid, connector_addr in get_vm_connectors():
        check_and_kill_deadlocked_vm(pid, connector_addr)


if __name__ == "__main__":
    main()