Infinite repetition of `AttributeError: '_UnixSelectorEventLoop' object has no attribute '_ssock'` when exception raised in log handler

[gerritholl]

When an exception occurs in a logging handler and I run the script through ipdb, ipdb attempts to stop at the exception. This results in an infinite repetition of AttributeError: '_UnixSelectorEventLoop' object has no attribute '_ssock' alternating with the custom exception in the log handler.

Running this script with python -mipdb:

import sys
import logging

class MyHandler(logging.StreamHandler):
    def emit(self, record):
        raise RuntimeError("nooo")
        super().emit(record)

logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
logger.addHandler(MyHandler(sys.stderr))
logger.warning("test")

an excerpt from the console output:

  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/unix_events.py", line 58, in close
    super().close()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/selector_events.py", line 92, in close
    self._close_self_pipe()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/selector_events.py", line 99, in _close_self_pipe
    self._remove_reader(self._ssock.fileno())
AttributeError: '_UnixSelectorEventLoop' object has no attribute '_ssock'
Post mortem debugger finished. The mwe108.py will be restarted
> /home/gholl/checkouts/2019_iafe/devel_code/mwe/mwe108.py(1)<module>()
----> 1 import sys
      2 import logging
      3

Exception in thread Thread-29889:
Traceback (most recent call last):
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/prompt_toolkit/application/application.py", line 807, in run
    loop = get_event_loop()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/events.py", line 639, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'Thread-29889'.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/IPython/terminal/debugger.py", line 122, in in_thread
    line = self.pt_app.prompt()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/prompt_toolkit/shortcuts/prompt.py", line 1013, in prompt
    return self.app.run(set_exception_handler=set_exception_handler)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/prompt_toolkit/application/application.py", line 813, in run
    loop = new_event_loop()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/events.py", line 758, in new_event_loop
    return get_event_loop_policy().new_event_loop()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/events.py", line 656, in new_event_loop
    return self._loop_factory()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/unix_events.py", line 54, in __init__
    super().__init__(selector)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/selector_events.py", line 59, in __init__
    logger.debug('Using selector: %s', selector.__class__.__name__)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1422, in debug
    self._log(DEBUG, msg, args, **kwargs)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1577, in _log
    self.handle(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1587, in handle
    self.callHandlers(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1649, in callHandlers
    hdlr.handle(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 950, in handle
    self.emit(record)
  File "/home/gholl/checkouts/2019_iafe/devel_code/mwe/mwe108.py", line 6, in emit
    raise RuntimeError("nooo")
RuntimeError: nooo
Exception ignored in: <function BaseEventLoop.__del__ at 0x7f695ff63430>
Traceback (most recent call last):
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/base_events.py", line 656, in __del__
    self.close()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/unix_events.py", line 58, in close
    super().close()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/selector_events.py", line 92, in close
    self._close_self_pipe()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/selector_events.py", line 99, in _close_self_pipe
    self._remove_reader(self._ssock.fileno())
AttributeError: '_UnixSelectorEventLoop' object has no attribute '_ssock'
Traceback (most recent call last):
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/ipdb/__main__.py", line 276, in main
    pdb._runscript(mainpyfile)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/pdb.py", line 1573, in _runscript
    self.run(statement)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/bdb.py", line 580, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "/home/gholl/checkouts/2019_iafe/devel_code/mwe/mwe108.py", line 1, in <module>
    import sys
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1446, in warning
    self._log(WARNING, msg, args, **kwargs)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1577, in _log
    self.handle(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1587, in handle
    self.callHandlers(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1649, in callHandlers
    hdlr.handle(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 950, in handle
    self.emit(record)
  File "/home/gholl/checkouts/2019_iafe/devel_code/mwe/mwe108.py", line 6, in emit
    raise RuntimeError("nooo")
RuntimeError: nooo
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /home/gholl/checkouts/2019_iafe/devel_code/mwe/mwe108.py(6)emit()
      5     def emit(self, record):
----> 6         raise RuntimeError("nooo")
      7         super().emit(record)

Exception in thread Thread-29890:
Traceback (most recent call last):
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/prompt_toolkit/application/application.py", line 807, in run
    loop = get_event_loop()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/events.py", line 639, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
RuntimeError: There is no current event loop in thread 'Thread-29890'.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/IPython/terminal/debugger.py", line 122, in in_thread
    line = self.pt_app.prompt()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/prompt_toolkit/shortcuts/prompt.py", line 1013, in prompt
    return self.app.run(set_exception_handler=set_exception_handler)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/prompt_toolkit/application/application.py", line 813, in run
    loop = new_event_loop()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/events.py", line 758, in new_event_loop
    return get_event_loop_policy().new_event_loop()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/events.py", line 656, in new_event_loop
    return self._loop_factory()
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/unix_events.py", line 54, in __init__
    super().__init__(selector)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/asyncio/selector_events.py", line 59, in __init__
    logger.debug('Using selector: %s', selector.__class__.__name__)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1422, in debug
    self._log(DEBUG, msg, args, **kwargs)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1577, in _log
    self.handle(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1587, in handle
    self.callHandlers(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 1649, in callHandlers
    hdlr.handle(record)
  File "/data/gholl/miniconda3/envs/py38/lib/python3.8/logging/__init__.py", line 950, in handle
    self.emit(record)
  File "/home/gholl/checkouts/2019_iafe/devel_code/mwe/mwe108.py", line 6, in emit
    raise RuntimeError("nooo")
RuntimeError: nooo
Exception ignored in: <function BaseEventLoop.__del__ at 0x7f695ff63430>
Traceback (most recent call last):

...and this repeats on indefinitely. The only change I can see is that the thread ID increases by one.

Attempting to interrupt this with Ctrl+C stops the deluge of console output and instead adds a single line ^C--KeyboardInterrupt--, but does not stop the programme. Interrupting with Ctrl+</kbd> stops the programme with ^\Quit (core dumped).

With regular pdb this problem does not occur, instead I am put into the debugger where the exception is raised.

I'm using ipdb 0.13.3, ipython 7.18.1, python 3.8.6, on openSUSE 15.0.

[gotcha]

ipdb is a light wrapper arount IPython debugger.

I see in the traceback that there is an issue with prompt-toolkit which makes me believe this is an issue to be reported to IPython.