Support no-GIL (free-threaded) Python

[btakita]

What version of gRPC and what language are you using?

Python 3.13.2t
grpcio==1.70.0

What operating system (Linux, Windows,...) and version?

Linux 6.13.2-zen1-1-zen x86_64 unknown

What runtime / compiler are you using (e.g. python version or version of gcc)

Python 3.13.2t

What did you do?

In a virtual env environment, attempt a pip install.

What did you expect to see?

A successful install.

What did you see instead?

install-grpcio-err.txt

Anything else we should know about your project / environment?

Using Virtual Env & pip install.

[sreenithi]

Hi @btakita , thanks for bringing this up. gRPC Python currently uses GIL internally, and we don't yet support no-GIL mode. This is currently in our backlog, and we do not have the bandwidth to pick this up yet.

However, we would like to welcome any external contributions for the same.
And for any users who are also interested in this support, please continue to add your comments, so that we can re-assess priority based on community interest.

[rinarakaki]

We eagerly request the free-threading/no-GIL Python support (cp313t wheel)!

[rinarakaki]

Seems the error comes from the Cython layer?

These are the official documents, just to share with those who aren't familiar with the situation:

• Users Guide > Cython and the GIL
• Users Guide > Free threading

[rgommers]

Definitely of interest!

For Cython, the latest release (3.0.12, or the 3.0.x series) does not support free-threading. Cython's master branch does though, and is successfully used by quite a few projects now. There are also nightly wheels for Cython that support free-threading at https://anaconda.org/scientific-python-nightly-wheels/cython (and that is documented at
https://py-free-threading.github.io/debugging/#cython-compilation-errors-unknown-type-name-__pyx_vectorcallfunc).

For building wheels with cibuildwheel in CI, numpy and other projects use this to pull in a Cython nightly specifically for cp313t wheels:
https://github.com/numpy/numpy/blob/01e98f1098a8a40df80bda98a3e8ea714b979010/tools/wheels/cibw_before_build.sh#L56-L63