Vinay Sajip <vinay_sa...@yahoo.co.uk> added the comment:
This had dropped off my radar completely, but I still can't see where there's
an actual bug here. This simplified script:
import logging
import sys
LOGGING = {
'version': 1,
'handlers': {
'logfile': {
'level': 'DEBUG',
'class': 'logging.FileHandler',
'filename': '/tmp/debug.log',
},
},
}
print('Starting: %s' % sys.version)
from logging.config import dictConfig
dictConfig(LOGGING)
print('After dictconfig')
print('_handlerList 1, initial:', logging._handlerList, len(logging._handlers))
import importlib
print('_handlerList 2, about to import shutil:', logging._handlerList,
len(logging._handlers))
import shutil
print('_handlerList 3, just imported shutil:', logging._handlerList,
len(logging._handlers))
print('')
when run with Python 3.10, produces
Starting: 3.10.0+ (heads/3.10:7203ecd332, Oct 29 2021, 10:04:19) [GCC 7.5.0]
After dictconfig
_handlerList 1, initial: [<weakref at 0x7f3e25e9e070; to 'FileHandler' at
0x7f3e25e63dc0>] 1
_handlerList 2, about to import shutil: [<weakref at 0x7f3e25e9e070; to
'FileHandler' at 0x7f3e25e63dc0>] 1
/home/vinay/.local/lib/python3.10/_compression.py:33: ResourceWarning: unclosed
file <_io.FileIO name='/tmp/debug.log' mode='ab' closefd=True>
class DecompressReader(io.RawIOBase):
ResourceWarning: Enable tracemalloc to get the object allocation traceback
_handlerList 3, just imported shutil: [] 0
But ... there are no loggers that use this handler, so the only reference would
be the weak reference in _handlerList - it gets freed up at some point (in this
case, when shutil is imported, but I don't believe that's necessarily relevant)
and that causes the ResourceWarning, but where's the problem? If you either add
a reference to the handler (by adding it to a logger) or adding "delay: True"
to the handler configuration dict to delay opening the file, the
ResourceWarning is no longer seen.
I tested with Python 3.4 - 3.10 and all versions behave the same way - it could
just be down to where weak references get dumped, which is down to the vagaries
of GC. I don't see this as a "leak" - the ResourceWarning is showing the
developer that they opened a file for no particular reason and didn't use it.
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue23010>
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