[issue4749] Issue with RotatingFileHandler logging handler on Windows

Vinay Sajip report at bugs.python.org
Tue Jun 9 18:48:17 CEST 2009

Vinay Sajip <vinay_sajip at yahoo.co.uk> added the comment:

Debugging threading problems is never as simple as it seems. I don't
believe logging is breaking because of some interaction with the system
calls - rather, the presence of the system calls is changing the
real-time characteristics of the system and exposing the failure.

This problem is not directly related to logging - for example, see


I will look to see if I can find what the exact problem is. Did you turn
off Windows search indexing for the volume before running the test, in
addition to turning off the anti-virus? It looks as if something else is
opening the file (which, in our test, will have been very recently
written to when the error occurs) and the suspicion must fall on
anti-virus or search indexing or some other file watching software (e.g.
backup software which is configured to monitor all file changes and
refresh the backup copy in pseudo-real-time).


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