error at telnet shutdown in Python 3

[kmike]

Scrapy version:

Scrapy    : 1.3.3
lxml      : 3.7.3.0
libxml2   : 2.9.3
cssselect : 1.0.1
parsel    : 1.1.0
w3lib     : 1.17.0
Twisted   : 17.1.0
Python    : 3.5.2 (default, Nov 17 2016, 17:05:23) - [GCC 5.4.0 20160609]
pyOpenSSL : 0.15.1 (OpenSSL 1.0.2g  1 Mar 2016)
Platform  : Linux-4.4.0-59-generic-x86_64-with-Ubuntu-16.04-xenial

I've got this exception on shutdown:

2017-04-05 18:18:10 [scrapy.core.engine] INFO: Spider closed (finished)
2017-04-05 18:18:10 [scrapy.utils.signal] ERROR: Error caught on signal handler: <bound method TelnetConsole.stop_listening of <scrapy.extensions.telnet.TelnetConsole object at 0x7fbb993bfeb8>>
Traceback (most recent call last):
  File "/home/ubuntu/.local/lib/python3.5/site-packages/twisted/internet/defer.py", line 150, in maybeDeferred
    result = f(*args, **kw)
  File "/home/ubuntu/.local/lib/python3.5/site-packages/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/home/ubuntu/.local/lib/python3.5/site-packages/scrapy/extensions/telnet.py", line 63, in stop_listening
    self.port.stopListening()
AttributeError: 'TelnetConsole' object has no attribute 'port'

Not sure if it is a real problem, but it'd be nice to shut down without error messages. No idea how to reproduce it, I've only seen it once.

[timfeirg]

I'm using scrapy 1.3.3 with python 3.6.1, didn't see this while using the telnet console

[cclauss]

This would happen if the TelnetConsole was initialzed but never had its start_listening() method called because self.port is currently not defined in the former but is only defined in the latter.

Fix proposed in #2892

[Gallaecio]

Should we close this until there is a way to reproduce it?

[cclauss]

As discussed above, there is a way of reproducing it. Initialize the TelnetConsole but do not call its .start_listening() method.

[Gallaecio]

I don't understand why the error happens in a first place - why can start_listening call be missed
#2892 (comment)

[Gallaecio]

@cclauss My understanding is that the original issue was triggered without manually interacting with the TelnetConsole class. So there is no human interaction with the class itself. Which means that the root issue most likely could be (or have been?) in some other code that directly or indirectly handles the TelnetConsole class. And #6224 would hide that issue (again, if such an issue currently exists, which is not clear).

[cclauss]

The original request was:

Not sure if it is a real problem, but it'd be nice to shut down without error messages. No idea how to reproduce it, I've only seen it once.

I broke that down into two requests:

it'd be nice to shut down without error messages

That was #2892

No idea how to reproduce it

That was #6224

If you do not want questions answered then please refrain from opening issues.