=============================================== GeventMP_ - Gevent_ Multiprocessing Extension

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.. warning:: HIC SUNT DRACONES!!!

This code is experimental (beta). There is some testing, but a lots of things are in flux, and
some platforms don't work at all.

You MAY try to use this in production with the understanding that this is a beta-quality software.

That said, this code may crash your server, bankrupt your company, burn your house down and be mean
to your puppy.

You've been warned.

Problem

Due to internal implementation, multiprocessing (MP) is unsafe to use with Gevent_ even when monkey-patched__. Namely, the use of OS semaphore primitives and inter-process IO in MP will cause the main loop to stall/deadlock/block (specific issue depends on the version of CPython).

__ monkey_

Solution

GeventMP_ (Gee-vent Em-Pee) is a gevent_ multiprocessing extension plugin for the monkey-patching__ subsystem. As with the rest of the monkey patch subsystem the process is fairly clear:

__ monkey_

1. Identify all places where blocking occurs and where it may stall the loop.
2. If blocking occurs on a file descriptor (FD), try to convert the file descriptor from blocking to non-blocking (sockets/pipes/fifos, sometimes even files where, rarely, appropriate) and replace blocking IO functions with their gevent_ non-blocking equivalents.
3. If blocking occurs in a Python/OS primitive that does not support non-blocking access and thus cannot be geventized, wrap all blocking access to that primitive with native thread-pool-based wrappers and call it a day (while fully understanding that primitive access latency will increase and raw performance may suffer as a result).
4. If you are really brave and have lots of free time on your hands, completely replace a standard blocking Python non-FD-based primitive with implementation based on an FD-based OS primitive (e.g. POSIX semaphore => Linux eventfd-based semaphore for kernels > 2.6.30__).
5. Due to launching of separate processes in MP, figure out how, when, and whether to monkey-patch__ spawned/forked children and grandchildren.

__ eventfd_

__ monkey_

Installation

The package is hosted on PyPi_.

For stable version:

.. code-block:: bash

pip install geventmp

For unstable version:

.. code-block:: bash

pip install --pre geventmp

Once installed, GeventMP_ will activate by default in the below stanza.

.. code-block:: python

from gevent.monkey import patch_all patch_all()

If you would like GeventMP_ to not activate by default, either do not install it or explicitly disable it:

.. code-block:: python

from gevent.monkey import patch_all patch_all(geventmp=False)

That's it - there are no other flags, settings, properties or config values so far.

Supported Platforms

.. note:: All claims of support may not be real at all. You're welcome to experiment. See warnings on top.

• Linux and Darwin.
• CPython 3.7, 3.8, 3.9, 3.10, 3.11, 3.12
• PyPy 3.8, 3.9

Known Issues

• Multiprocessing forkserver works in GeventMP_, but the spawned child isn't green.

TODO

1. Monkey patch Windows to the extent possible.
2. Lots of applications use Billiard <https://github.com/celery/billiard>_ for multiprocessing instead of stock Python package. Consider monkey patching Billiard if detected.

Contact Us

Post feedback and issues on the Bug Tracker, Gitter, and Twitter (@karelleninc)_.

.. _Gevent: https://github.com/gevent/gevent/ .. _geventmp: https://github.com/karellen/geventmp .. _bug tracker: https://github.com/karellen/geventmp/issues .. _gitter: https://gitter.im/karellen/Lobby .. _twitter (@karelleninc): https://twitter.com/karelleninc .. _monkey: https://en.wikipedia.org/wiki/Monkey_patch .. _eventfd: https://linux.die.net/man/2/eventfd .. _pypi: https://pypi.org/project/geventmp/