Threaded server

[Diez B. Roggisch]

Giampaolo Rodola' wrote:

> On 14 Gen, 12:30, Nick Craig-Wood <n... at craig-wood.com> wrote:
>> Giampaolo Rodola' <gne... at gmail.com> wrote:
>> > I'm trying to run an asynchronous FTP server I wrote into a thread for
>> > being able to run a test suite against it.
>> > The code below is the threaded FTP server code I'm using:
>>
>> > class FTPd(threading.Thread):
>>
>> > def __init__(self):
>> > self.active = False
>> > threading.Thread.__init__(self)
>>
>> > def start(self, flag=None):
>> > assert not self.active
>> > self.flag = flag
>> > threading.Thread.start(self)
>>
>> > def run(self):
>> > assert not self.active
>> > ftpd = ftpserver.FTPServer(address, ftp_handler)
>> > if self.flag:
>> > self.flag.set()
>> > self.active = True
>> > while self.active:
>> > ftpd.server_forever(timeout=1, count=1)
>> > ftpd.close()
>>
>> > def stop(self):
>> > assert self.active
>> > self.active = False
>>
>> > flag = threading.Event()
>> > ftpd = FTPd()
>> > ftpd.start(flag)
>> > flag.wait()  # wait for it to start
>> > unittest.main() # run the test suite
>> > ftpd.stop()
>>
>> > Sometimes I get a strange error when all the tests have finished, the
>> > server is stopped and Python is exiting:
>>
>> > Ran 50 tests in 1.515s
>>
>> > OK
>> > Exception exceptions.TypeError: "'NoneType' object is not callable" in
>> > <bound me
>> > thod FTPHandler.__del__ of <pyftpdlib.ftpserver.FTPHandler connected
>> > 127.0.0.1:2
>> > 249 at 0xa4b080>> ignored
>> > Exception exceptions.TypeError: "'NoneType' object is not callable" in
>> > <bound me
>> > thod FTPServer.__del__ of <pyftpdlib.ftpserver.FTPServer listening
>> > 127.0.0.1:543
>> > 21 at 0x9e1a30>> ignored
>>
>> > I sincerely don't know why that happens but it's likely because I'm
>> > not using threads properly.
>> > My concern is that this could be caused by a sort of race condition
>> > (e.g. Python tries to exit when ftpd.close call is not yet
>> > completed).
>>
>> It looks like when python is shutting down, it has removed an object
>> the ftphandler code relies on.
>>
>> I see you attempt to kill the ftp server with ftpd.stop().  That is
>> good, but you don't wait for the thread to finish (it might take up to
>> a second in ftpd.server_forever if I understand correctly).
>>
>> I expect if you put a self.join() at the end of the stop() method the
>> problem will go away.
>>
>> --
>> Nick Craig-Wood <n... at craig-wood.com> --http://www.craig-wood.com/nick-
>> Nascondi testo tra virgolette -
>>
>> - Mostra testo tra virgolette -
> 
> Tried it but the problem remains.
> The strange thing is that it sometimes happens, sometimes doesn't.

AFAIK you can safely ignore this error. It essentially stems from
non-determinism when shutting down threads. 

Diez