Add a keyword-only `on_error` parameter to `multiprocessing.set_forkserver_preload()`. This allows the user to have exceptions during optional `forkserver` start method module preloading cause the forkserver subprocess to warn (generally to stderr) or exit with an error (preventing use of the forkserver) instead of being silently ignored.
This _also_ fixes an oversight, errors when preloading a `__main__` module are now treated the similarly. Those would always raise unlike other modules in preload, but that had gone unnoticed as up until bug fix PR GH-135295 in 3.14.1 and 3.13.8, the `__main__` module was never actually preloaded.
Based on original work by Nick Neumann @aggieNick02 in GH-99515.
* Document the ctx parameter in some types in multiprocessing.
* Reduce duplication while still linking to the central explanation from API points with the side effect.
Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
Co-authored-by: R Chintan Meher <meherrihaan@gmail.com>
* Doc: Remove sencence implying that concurrent.futures.ThreadPoolExecutor does not exist
Closes#140578
* Add NEWS.d entry for gh-140578
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Co-authored-by: Louis Paternault <spalax@gresille.org>
* Reword, expand, and clarify the limitation, highlighting the REPL case.
* Mention in the high level Process description.
* added a pointer to the GH issue from the doc note
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Co-authored-by: Gregory P. Smith <greg@krypto.org>
Add a copy of the text from SimpleQueue.close()
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Co-authored-by: saggarwal145 <saggarwal145@bloomberg.net>
Co-authored-by: Petr Viktorin <encukou@gmail.com>
Doc/library/multiprocessing.rst: freeze_support: Change to specify spawn method instead of platform
Have multiprocessing.freeze_support() enable on spawn, not just win32.
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Co-authored-by: Gregory P. Smith <greg@krypto.org>
Change the default multiprocessing start method away from fork to forkserver or spawn on the remaining platforms where it was fork. See the issue for context. This makes the default far more thread safe (other than for people spawning threads at import time... - don't do that!).
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: Russell Keith-Magee <russell@keith-magee.com>
Co-authored-by: T. Wouters <thomas@python.org>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: Jacob Coffee <jacob@z7x.org>
Co-authored-by: Malcolm Smith <smith@chaquo.com>
Co-authored-by: Ned Deily <nad@python.org>
Document the `os.fork` posix threads detected `DeprecationWarning` in 3.12 What's New, os, multiprocessing, and concurrent.futures docs.
Many reviews and doc cleanup edits by Adam & Hugo. 🥳
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
