I have a threaded Python daemon. Like any good daemon, it wants to launch all of its worker threads, then wait around until it's told to terminate. The normal signal for termination is SIGTERM
, and in most languages I'd hold to terminate by waiting on an event or mutex, so using threading.Event
made sense to me. The problem is that Python's Event
object and Unix signals don't appear to be playing well together.
This works as expected, terminating on SIGTERM
:
import signal
import time
RUN = True
def handle(a, b):
global RUN
print "handled"
RUN = False
signal.signal(signal.SIGTERM, handle)
while RUN:
time.sleep(0.250)
print "Stopping"
but this results in no SIGTERM
being delivered (i.e., quite apart from quitting, "handled" never gets printed):
import signal
import threading
RUN_EVENT = threading.Event()
def handle(a, b):
print "handled"
RUN_EVENT.set()
signal.signal(signal.SIGTERM, handle)
RUN_EVENT.wait()
print "Stopping"
So my question is:
- Am I misusing
threading.Event
in some way?
- If I am not, is there an alternative other than the poll-and-sleep mechanism from the first example?
- Also if I am not, why does using
threading.Event
kill the signal handler?
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