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spacemanspiff2007 opened this issue Sep 27, 2024 · 3 comments
Open

Profilers do not work in threads #124656

spacemanspiff2007 opened this issue Sep 27, 2024 · 3 comments
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docs Documentation in the Doc dir

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@spacemanspiff2007
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spacemanspiff2007 commented Sep 27, 2024 •
edited by bedevere-app bot
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Bug report

Bug description:

This issue is related to, but not the same as #110770.
Running two profilers in parallel threads raises an unexpected error.
It's not clear at all that the profiler will not work in parallel.
Either this is a bug or there should be a prominent warning in the docs.

import time
from cProfile import Profile
from threading import Thread


def task_sleep() -> None:

    pr = Profile()
    pr.enable()
    time.sleep(1)
    pr.disable()


t1 = Thread(target=task_sleep)
t2 = Thread(target=task_sleep)

t1.start()
t2.start()

t1.join()
t2.join()
Exception in thread Thread-2 (task_sleep):
ValueError: Another profiling tool is already active

CPython versions tested on:

3.12

Operating systems tested on:

Windows

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@spacemanspiff2007 spacemanspiff2007 added the type-bug An unexpected behavior, bug, or error label Sep 27, 2024
@ZeroIntensity
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Yeah, you can't use multiple profilers at once. This is sort of documented, see sys.monitoring.use_tool_id:

Raises a ValueError if tool_id is in use.

I guess it's not explicitly mentioned in the cProfile documentation, though.

@AA-Turner AA-Turner added docs Documentation in the Doc dir and removed type-bug An unexpected behavior, bug, or error labels Sep 27, 2024
@AA-Turner
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Recategorising as a documentation problem, a PR is welcome.

A

@bedevere-app bedevere-app bot mentioned this issue Sep 27, 2024
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@gaogaotiantian
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This was a new behavior for 3.12, but even before 3.12, this code would not "work" - it wouldn't raise an error either. Anyway, I believe we should document it somewhere in cProfile's doc. @AA-Turner is great with the docs so I'll leave the review to him.

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@AA-Turner @spacemanspiff2007 @gaogaotiantian @ZeroIntensity