Cancel threads at the end of execution

[bjorn-spire]

Because lambda doesn't actually stop the Python processes proper after each execution the threads would linger around after finishing. After enough invocations of your function it would start failing from:

  error: can't start new thread
   File "raven_python_lambda/__init__.py", line 176, in decorated
     install_timers(self.config, context)
   File "raven_python_lambda/__init__.py", line 231, in install_timers
     Timer(max(time_remaining - 500, 0), timeout_error, (config)).start()
   File "python2.7/threading.py", line 739, in start
     _start_new_thread(self.__bootstrap, ())  

By collecting all the timers and then canceling them at the end of function execution we're no longer seeing this resource constraint.

Also fixed a completely unrelated bug with time_remaining. While writing the test I got an invocation of it and saw that it couldn't run because the config object was splatted out to 8 arguments instead of the one config as expected. :)

[bjorn-spire]

Oh, to validate that the threads aren't killed between invocations I created a new lambda and ran it a couple of times and saw that the count went up:

from threading import Timer, active_count

def handler(event, context):
    def end_of_timer():
        print('end of timer!')

    t = Timer(290, end_of_timer)
    t.start()

    print('Currently active threads: {}'.format(active_count()))

[kevgliss]

Thats a good point. We hadn't noticed this previously.