Ctrl+c) interrupt the excution of the
multiprocess.Pool, it will not work as expected. Following is a demo
import time from multiprocessing import Pool def worker(): while True: time.sleep(1) pool = Pool(1) pool.apply(worker)
When run the code and try to
Ctrl+C to stop it, it will never be stopped.
$ python2 b.py ^CProcess PoolWorker-1: Traceback (most recent call last): File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap self.run() File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run self._target(*self._args, **self._kwargs) File "/usr/lib/python2.7/multiprocessing/pool.py", line 113, in worker result = (True, func(*args, **kwds)) File "b.py", line 7, in worker time.sleep(1) KeyboardInterrupt
This is a Python bug. When waiting for a condition in threading.Condition.wait(), KeyboardInterrupt is never sent. Repro:import threading cond = threading.Condition(threading.Lock()) cond.acquire() cond.wait(None) print "done"The KeyboardInterrupt exception won't be delivered until wait() returns, and it never returns, so the interrupt never happens. KeyboardInterrupt should almost certainly interrupt a condition wait. Note that this doesn't happen if a timeout is specified; cond.wait(1) will receive the interrupt immediately. So, a workaround is to specify a timeout. To do that, replaceresults = pool.map(slowly_square, range(40))withresults = pool.map_async(slowly_square, range(40)).get(9999999)or similar.
By using this, we can interrupt the Pool by using
Here is a better version.
import multiprocessing from multiprocessing import Pool import time import signal def worker(): while True: print time.time() time.sleep(.5) def worker_init(): # ignore the SIGINI in sub process, just print a log def sig_int(signal_num, frame): print 'signal: %s' % signal_num signal.signal(signal.SIGINT, sig_int) pool = Pool(2, worker_init) result = pool.apply_async(worker) while True: try: result.get(0xfff) # catch TimeoutError and get again except multiprocessing.TimeoutError as ex: print 'timeout'
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