"""
Using Python 3.6.0 (python3.6 test.py):

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/multiprocessing/queues.py", line 241, in _feed
    obj = _ForkingPickler.dumps(obj)
  File "/usr/local/lib/python3.6/multiprocessing/reduction.py", line 51, in dumps
    cls(buf, protocol).dump(obj)
TypeError: can't pickle _thread.RLock objects

---------------
No issues in Python 3.5.x
"""

import concurrent.futures
import sys
import time


class Processor():

    def __init__(self):
        self._futures = set()

    def _consume(self, d):
        print(d)

    def start(self):
        while 1:
            try:
                with concurrent.futures.ProcessPoolExecutor(
                        max_workers=8) as executor:
                    while 1:
                        for n in range(10):
                            future = executor.submit(self._consume, n)
                            self._futures.add(future)
                        time.sleep(5)
            except concurrent.futures.process.BrokenProcessPool:
                for f in self._futures:
                    f.cancel()
                executor.shutdown()
            except KeyboardInterrupt:
                for f in self._futures:
                    f.cancel()
                sys.exit(0)
            time.sleep(5)


def main():
    processor = Processor()
    processor.start()


if __name__ == '__main__':
    main()