Fork is not available on windows

[PanagiotisS]

Hello.

I have encountered the following error on windows,

ValueError: cannot find context for 'fork'

Fork (or forkserver) is not available on windows, https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods

The issue if from the following line

72bc089#diff-b3b1f4cc344f3013a1b743b1876cb3e6e9848d15aab3ffbb48067978419a1a1aR446-R451

def _set_multiprocessing_start_method() -> None:
    # this is currently required because the latest litestar uses a QueueListener logging handler
    if platform.system() in {"Darwin", "Windows"}:
        multiprocessing.set_start_method("fork", force=True)

If I change the following line to

-        multiprocessing.set_start_method("fork", force=True)
+        multiprocessing.set_start_method("spawn", force=True)

or even if I ignore the line completely (on Windows),

-    if platform.system() in {"Darwin", "Windows"}:
+    if platform.system() in {"Darwin"}:

it works fine.

Minimal example:

# app.py
from litestar import Controller, Litestar, get
from litestar.logging import LoggingConfig
from litestar_granian import GranianPlugin


class SampleController(Controller):
    @get(path="/sample")
    async def sample_route(self) -> dict[str, str]:
        """Sample Route."""
        return {"sample": "hello-world"}


logging_config = LoggingConfig(
    root={"level": "INFO", "handlers": ["queue_listener"]},
    formatters={
        "standard": {"format": "%(asctime)s - %(name)s - %(levelname)s - %(message)s"}
    },
    log_exceptions="always",
)
logger = logging_config.configure()()

app = Litestar(
    plugins=[GranianPlugin()],
    route_handlers=[SampleController],
    logging_config=logging_config,
)

# pyproject.toml
[project]
name = "test"
version = "1.0.0"
requires-python = "==3.12.*"

dependencies = [
    "litestar",
    "litestar-granian",
]

Versions:

• python version: Python 3.12.6
• windows 11
• litestar: 2.12.1
• litestar-granian: 0.7.1
• granian: 1.6.3

P.S.
Regarding the comment,

# this is currently required because the latest litestar uses a QueueListener logging handler

I indeed had this problem after the commit e1f1485 and I had set this to True in my code, but I see this was changed back to True as a default.

Thank you.
Best wishes.