Vinay Sajip <vinay_sa...@yahoo.co.uk> added the comment:
I had to delete my previous response to the initial post, as something got
mangled in it. Here's what I meant to say:
----------------------------------------------
It sounds to me as if there's a problem in yum that needs sorting out: I'm not
sure why it would need dozens of loggers.
As your workaround snippet shows, leaking files is not due to loggers but due
to handlers - they're a different animal. Handlers need not be leaked - they
can just be closed when you're done with them. Handlers *are* stored with weak
references.
The design contract for loggers precludes using weak references for them. For
example, if I use a library and from my logging initialization code get a
reference to its top-level logger and e.g. set that logger's level, then when
I've finished, there may not be any other references to that logger until I do
an import of some library module. I wouldn't want the reference to the logger
to go away, because then the library wouldn't know my intention regarding the
level setting.
Normal practice would be to add a few handlers to yum's top-level logger and
let descendant loggers inherit them. I'm not familiar with yum, so I don't know
if/why it deviates from this common and best practice approach.
As you state, replacing {} with WeakValueDictionary() wouldn't solve the
problem, and would violate the design assumptions/contract relating to loggers.
By the way, the logging module does not store loggers in lists and dicts - just
in a single dict in a manager. Handlers are stored in weak reference dicts as
well as lists but that does not mean they are guaranteed to be garbage
collected, since there could also be references to them in user code. Likewise
for loggers - typically there would be references to them in lines like
logger = logging.getLogger(__name__)
in numerous modules. Even if yum consists of dozens of modules (which perhaps
explains dozens of loggers), they needn't leak files, as just adding a single
FileHandler to yum's top-level logger would serve to capture logging events
from the entire yum package hierarchy.
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue11950>
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