Allow worker kwargs

[SaravananSathyanandhaQC]

Summary

Addresses #2377

This PR allows passing worker_kwargs to all workers when using uvicorn.run. This is more flexible than using environment variables because it means you can

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[lekeeith]

in my test，i can not get worker_kwargs as what i expect.
i have tow py file, run.py and a.py.
run.py as flow

from pathlib import Path
import uvicorn
import a
app = a.app
print("-------- queue  ----------")
if __name__ == '__main__':
    max_workers = 4
    uvicorn.run(f"{Path(a.__file__).stem}:app", host='0.0.0.0', port=8000, reload=True,
        worker_kwargs={"shared_queue": [1, 2, 3, 4]})

a.py as follow

from fastapi import FastAPI
app = FastAPI()

@app.get("/city/{city_id}")
def get_city(city_id: str):
    return {"city_id": city_id, "app": dir(app)}

curl

result

{
  "city_id": "123",
  "app": [
    "__call__",
    "__class__",
    "__delattr__",
    "__dict__",
    "__dir__",
    "__doc__",
    "__eq__",
    "__format__",
    "__ge__",
    "__getattribute__",
    "__gt__",
    "__hash__",
    "__init__",
    "__init_subclass__",
    "__le__",
    "__lt__",
    "__module__",
    "__ne__",
    "__new__",
    "__reduce__",
    "__reduce_ex__",
    "__repr__",
    "__setattr__",
    "__sizeof__",
    "__str__",
    "__subclasshook__",
    "__weakref__",
    "add_api_route",
    "add_api_websocket_route",
    "add_event_handler",
    "add_exception_handler",
    "add_middleware",
    "add_route",
    "add_websocket_route",
    "api_route",
    "build_middleware_stack",
    "contact",
    "debug",
    "delete",
    "dependency_overrides",
    "description",
    "docs_url",
    "exception_handler",
    "exception_handlers",
    "extra",
    "get",
    "head",
    "host",
    "include_router",
    "license_info",
    "middleware",
    "middleware_stack",
    "mount",
    "on_event",
    "openapi",
    "openapi_schema",
    "openapi_tags",
    "openapi_url",
    "openapi_version",
    "options",
    "patch",
    "post",
    "put",
    "redoc_url",
    "root_path",
    "root_path_in_servers",
    "route",
    "router",
    "routes",
    "separate_input_output_schemas",
    "servers",
    "setup",
    "state",
    "summary",
    "swagger_ui_init_oauth",
    "swagger_ui_oauth2_redirect_url",
    "swagger_ui_parameters",
    "terms_of_service",
    "title",
    "trace",
    "url_path_for",
    "user_middleware",
    "version",
    "webhooks",
    "websocket",
    "websocket_route"
  ]
}

in my opinion,i can get shared_queue in app but not.
i use what you changed code.

[SaravananSathyanandhaQC]

The option only applies when you use the factory option (maybe I should call it factory_kwargs), since then you have a function to return the app, and that function can get kwargs passed. If you use a single app like this then it will not work, it doesn't try to add attributes to the app itself (though that could be an alternate solution too).

If you made your a.py look like the following:

from fastapi import FastAPI

def app_creator(shared_queue = None):
    app = FastAPI()

    @app.get("/city/{city_id}")
    def get_city(city_id: str):
        return {"city_id": city_id, "shared_queue": shared_queue}

    return app

you should see the shared_queue passed.

If you actually intend to use this as a shared queue between workers that has items added/removed (as the variable name suggests at least) you should use a shared memory list or a SyncManager list