8000 Logging's msecs doesn't handle "100ms" well. · Issue #102402 · python/cpython · GitHub
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Logging's msecs doesn't handle "100ms" well. #102402

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dougthor42 opened this issue Mar 3, 2023 · 2 comments · Fixed by #102412
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Logging's msecs doesn't handle "100ms" well. #102402

dougthor42 opened this issue Mar 3, 2023 · 2 comments · Fixed by #102412
Labels
stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@dougthor42
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dougthor42 commented Mar 3, 2023 •
edited by bedevere-app bot
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Bug report

LogRecord.msecs returns an incorrect value when timestamp (self.ct) value has exactly 100ms.

One liner check:

assert int((1677793338.100_000_0 - int(1677793338.100_000_0)) * 1000) + 0.0 == 100.0

The issue is binary representation of "0.1" / floating point error:

>>> # Definition of LogRecord.msecs:
>>> # https://github.com/python/cpython/blob/12011dd8bafa6867f2b4a8a9e8e54cb0fbf006e4/Lib/logging/__init__.py#L343
>>> # int((ct - int(ct)) * 1000) + 0.0
>>> ct = 1677793338.100_000_0
>>> ct
1677793338.1
>>> ct - int(ct)
0.09999990463256836
>>> _ * 1000
99.99990463256836
>>> int(_)
99
>>> _ + 0.0
99.0

Your environment

  • CPython versions tested on:
    • 3.10.9
    • 3.11.2
  • Operating system and architecture:
    • Custom company OS based on Debian Testing
    • 64-bit

Discussion

I think switching to time.time_ns when setting the creation time might be one solution.

Linked PRs
@dougthor42 dougthor42 added the type-bug An unexpected behavior, bug, or error label Mar 3, 2023
@AlexWaygood AlexWaygood added the stdlib Python modules in the Lib dir label Mar 3, 2023
@vacosti
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vacosti commented Mar 3, 2023

I agree with @dougthor42 about the proposed solution, since time library itself suggests to "use time_ns() to avoid the precision loss caused by the float type".

@dougthor42
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I hope to find some time this weekend to implement a fix.

@dougthor42 dougthor42 mentioned this issue Mar 4, 2023
Merged
vsajip pushed a commit that referenced this issue Apr 16, 2024
@dougthor42
gh-102402: Fix floating point math issue by using time.time_ns() in…
1316692 
… `logging.LogRecord` (GH-102412)
diegorusso pushed a commit to diegorusso/cpython that referenced this issue Apr 17, 2024
@dougthor42 @diegorusso
pythongh-102402: Fix floating point math issue by using `time.time_ns…
c7c3707 
…()` in `logging.LogRecord` (pythonGH-102412)
vstinner added a commit to vstinner/cpython that referenced this issue Apr 17, 2024
@vstinner
pythongh-102402: Fix logging test_relativeCreated_has_higher_precisio…
2529340 
…n() leak

Fix a reference leak in test_relativeCreated_has_higher_precision()
of test_logging: don't reimport the logging the logging module.
@bedevere-app bedevere-app bot mentioned this issue Apr 17, 2024
Merged
vstinner added a commit that referenced this issue Apr 18, 2024
@vstinner
gh-102402: Fix logging test_relativeCreated_has_higher_precision() le…
8f25cc9 
…ak (#117985)

Fix a reference leak in test_relativeCreated_has_higher_precision()
of test_logging: don't reimport the logging the logging module.
serhiy-storchaka added a commit to serhiy-storchaka/cpython that referenced this issue Apr 18, 2024
@serhiy-storchaka
pythongh-102402: Make test_relativeCreated_has_higher_precision less …
74196ab 
…implementation dependent
@bedevere-app bedevere-app bot mentioned this issue Apr 18, 2024
Merged
serhiy-storchaka added a commit that referenced this issue Apr 30, 2024
@serhiy-storchaka
gh-102402: Make test_relativeCreated_has_higher_precision less implem…
02887c6 
…entation dependent (GH-118062)
SonicField pushed a commit to SonicField/cpython that referenced this issue May 8, 2024
@serhiy-storchaka @SonicField
pythongh-102402: Make test_relativeCreated_has_higher_precision less …
22ff9d6 
…implementation dependent (pythonGH-118062)
@bmerry bmerry mentioned this issue Jun 18, 2024
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gh-102402: Fix floating point math issue by using time.time_ns() in logging.LogRecord
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@dougthor42 @vacosti @AlexWaygood
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