René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"MemoryHandler can't be setup through a DictConfig if any other logger is setup after it","articleBody":"# Bug report\r\n\r\n### Bug description:\r\n\r\nThis is the logging that's failing.\r\n```python\r\nLOGGING = {\r\n    \"version\": 1,\r\n    \"disable_existing_loggers\": False,\r\n    \"handlers\": {\r\n        \"fine-logger1\": {\r\n            'level': logging.INFO,\r\n            'formatter': 'verbose-console',\r\n            'class': 'logging.StreamHandler',\r\n            'stream': 'ext://sys.stdout',\r\n        },\r\n        \"fine-logger2\": {\r\n            \"level\": logging.INFO,\r\n            \"class\": \"logging.FileHandler\",\r\n            \"filename\": Path(\"logs/somefilename.log\"),\r\n            \"mode\": \"a\",\r\n            \"formatter\": \"verbose\",\r\n        },\r\n        \"fine-logger3\": {\r\n            \"level\": logging.DEBUG,\r\n            \"class\": \"logging.FileHandler\",\r\n            \"filename\": Path(\"logs/errors/somefilename.log\"),\r\n            \"delay\": True,\r\n            \"formatter\": \"verbose\",\r\n        },\r\n        \"bugged-logger3\": {\r\n            \"level\": logging.DEBUG,\r\n            \"class\": \"logging.handlers.MemoryHandler\",\r\n            \"capacity\": 9999999,\r\n            \"flushLevel\": logging.ERROR,\r\n            \"target\": \"fine-logger3\",\r\n            \"flushOnClose\": False,\r\n        },\r\n    },\r\n    \"loggers\": {\r\n        \"bug-logger\": {\r\n            \"handlers\": [\"fine-logger1\", \"fine-logger2\", \"bugged-logger3\"],\r\n            \"level\": logging.DEBUG,\r\n            \"propagate\": True\r\n        },\r\n    },\r\n}\r\n```\r\nAfter it's been setup, if any other handler is setup afterwards (in my case it's the [copernicusmarine](https://pypi.org/project/copernicusmarine/) logger) the handler `bugged-logger3` will have a `None` inside its `target` field, as every handler that's not `incremental` will delete existing unused handlers.\r\n\r\nI've dug into the source code of logging and I think I've tracked down where this is happpening, but I'm not really sure on how to fix it.\r\nIn the config file `python3.11/logging/config.py` in the `configure()` function there's a call to `_clearExistingHandlers()`:\r\n```\r\n            else:\r\n                disable_existing = config.pop('disable_existing_loggers', True)\r\n\r\n                _clearExistingHandlers() \u003c-----\r\n\r\n                # Do formatters first - they don't refer to anything else\r\n                formatters = config.get('formatters', EMPTY_DICT)\r\n                for name in formatters:\r\n                    try:\r\n                        formatters[name] = self.configure_formatter(\r\n                                                            formatters[name])\r\n```\r\nIf we comment this line, it works completely fine. But I guess this just keeps handlers loaded in memory and that's not a proper solution.\r\n\r\n\r\n### CPython versions tested on:\r\n\r\n3.11\r\n\r\n### Operating systems tested on:\r\n\r\nLinux","author":{"url":"https://github.com/TheSylex","@type":"Person","name":"TheSylex"},"datePublished":"2024-08-22T17:02:49.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/123239/cpython/issues/123239"}