New submission from Bennie Swart :
The concurrent.futures.ThreadPoolExecutor class, which is the default asyncio
executor, introduced the _idle_semaphore field in version 3.8 in order to track
idle threads so they can be reused before increasing the pool size
unnecessarily.
This semaphore counter becomes unbalanced when the thread pool is
over-saturated, as can be seen in the file provided. This is due to workers
always incrementing the count after finishing a job, whereas the executor only
decrements the count if it is already greater than 0.
This seems to be a logic bug unrelated to the running environment and
introduced since python 3.8.
--
components: asyncio
files: bug.py
messages: 394017
nosy: asvetlov, bennieswart, yselivanov
priority: normal
severity: normal
status: open
title: ThreadPoolExecutor unbalanced semaphore count
type: behavior
versions: Python 3.8
Added file: https://bugs.python.org/file50054/bug.py
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<https://bugs.python.org/issue44188>
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