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gh-132372: Speed up logging.config existing logger handling #150242

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Merged
vsajip merged 4 commits into from
May 29, 2026
Merged

gh-132372: Speed up logging.config existing logger handling #150242

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55a64e2
gh-132372: Speed up logging.config existing logger handling
esadomer May 22, 2026
4040d60
gh-132372: Batch logging cache clearing
esadomer May 23, 2026
d076b07
gh-132372: Address logging config review comments
esadomer May 23, 2026
843bd2e
gh-132372: Use Logger.setLevel for preserved children
esadomer May 23, 2026
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gh-132372: Batch logging cache clearing 
Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>
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@esadomer @eendebakpt
esadomer and eendebakpt committed May 27, 2026
commit 4040d60321b083c7645c357313a0c2be8f3fa561
7 changes: 6 additions & 1 deletion Lib/logging/config.py
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Original file line number Diff line number Diff line change
Expand Up @@ -188,15 +188,20 @@ def _handle_existing_loggers(existing, child_loggers, disable_existing):
disabled if disable_existing is false.
"""
root = logging.root
cache_clear_needed = False
for log in existing:
logger = root.manager.loggerDict[log]
if log in child_loggers:
if not isinstance(logger, logging.PlaceHolder):
logger.setLevel(logging.NOTSET)
# Equivalent to setLevel(NOTSET), but clear the cache once.
logger.level = logging.NOTSET

@picnixz picnixz May 23, 2026

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Is this change really necessary? while setLevel would clear the cache multiple times, I would prefer that we pass through logger.setLevel public API instead of changing .level directly, just in case someone has a logger subclass that does something else with setLevel.

logger.handlers = []
logger.propagate = True
cache_clear_needed = True
else:
logger.disabled = disable_existing
if cache_clear_needed:
root.manager._clear_cache()

def _discard_existing_logger(name, existing, existing_set, child_loggers):

@picnixz picnixz May 23, 2026 •
edited
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Suggested change
def _discard_existing_logger(name, existing, existing_set, child_loggers):
def _forget_existing_logger(name, existing, existing_set, child_loggers):

Maybe something like that instead (since we also update child_loggers)

"""Discard a configured logger and record its existing children."""
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4 changes: 4 additions & 0 deletions Lib/test/test_logging.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4176,6 +4176,8 @@ def test_90195(self):
def test_disable_existing_loggers_preserves_children(self):
parent = logging.getLogger('many')
child = logging.getLogger('many.child')
child.setLevel(logging.CRITICAL)
self.assertFalse(child.isEnabledFor(logging.INFO))
cousin = logging.getLogger('many-child')
for i in range(20):
logging.getLogger(f'many-sibling-{i}')
Expand All @@ -4191,6 +4193,8 @@ def test_disable_existing_loggers_preserves_children(self):

self.assertFalse(parent.disabled)
self.assertFalse(child.disabled)
self.assertEqual(child.level, logging.NOTSET)
self.assertTrue(child.isEnabledFor(logging.INFO))
self.assertTrue(cousin.disabled)

def test_111615(self):
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