Suppose I've got a Python daemon that spawns a bunch of worker threads, waits
for a singal (e.g. SIGTERM) and then shuts down the worker threads gracefully.
What's the simplest way to do the signal handling portably across as many
operating systems as possible (at least Linux and FreeBSD). Specifically, I'm
interested in solutions where the main thread consumes no CPU, so no
time.sleep(n) loops.
The most obvious solution (below) does not work with on FreeBSD, because the
signal gets delivered to a different thread and signal.pause() doesn't return.
_shutdown = False
def sig_handler(signum, frame):
print 'handled'
global _shutdown
_shutdown = True
if __name__ == '__main__':
# Set up signal handling.
signal.signal(signal.SIGTERM, sig_handler)
# Start worker threads.
workers = [Worker() for i in xrange(NUM_THREADS)]
for worker in workers:
worker.start()
# Sleep until woken by a signal.
while not _shutdown:
signal.pause()
# Shutdown work threads gracefully.
for worker in workers:
worker.shutdown()
Any ideas? I've attached a more complete code sample.
Thanks
Duncan Findlay
import signal
import threading
NUM_THREADS = 2
class Worker(threading.Thread):
def __init__(self, *args, **kwargs):
threading.Thread.__init__(self, *args, **kwargs)
self._stop_event = threading.Event()
def run(self):
# Do something.
while not self._stop_event.isSet():
print 'hi from %s' % (self.getName(),)
self._stop_event.wait(10)
def shutdown(self):
self._stop_event.set()
print 'shutdown %s' % (self.getName(),)
self.join()
_shutdown = False
def sig_handler(signum, frame):
print 'handled'
global _shutdown
_shutdown = True
if __name__ == '__main__':
# Set up signal handling.
signal.signal(signal.SIGTERM, sig_handler)
# Start worker threads.
workers = [Worker() for i in xrange(NUM_THREADS)]
for worker in workers:
worker.start()
# Sleep until woken by a signal.
while not _shutdown:
signal.pause()
# Shutdown work threads gracefully.
for worker in workers:
worker.shutdown()
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