New submission from Ed Catmur <e...@catmur.uk>:
If a logging.FileHandler is configured with mode='w', or if logging.basicConfig is called with filemode='w' (as suggested by the Basic Logging Tutorial https://docs.python.org/3/howto/logging.html#logging-basic-tutorial) and if some code logs during shutdown, after logging has closed its handlers (asyncio is prone to do this, e.g.), then logging.FileHandler._open will reopen the log file with the same mode as it was originally opened with, potentially truncating it and losing valuable information: import atexit atexit.register(lambda: logging.info("so long")) import logging logging.basicConfig(filename='test.log', filemode='w', level=logging.INFO) logging.info("super important stuff") $ python truncate.py $ cat test.log INFO:root:so long I have a hunch that the fix to issue 26789 will potentially make things worse, as previously at least there was a chance that logging had been fully unloaded so that the call to open would fail. https://stackoverflow.com/questions/39838616/why-is-python-logging-framework-losing-messages ---------- components: Library (Lib) messages: 381146 nosy: ecatmur2 priority: normal severity: normal status: open title: logging reopens file with same mode, possibly truncating type: behavior versions: Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue42378> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
