These are the code files that (sort of) worked on my server to run Flask with Celery. Only some - not all - tasks get added to the Celery queue, and I'm not sure why. I adapted code from the offical Flask tutorial on Celery, Background Tasks with Celery, and consulted the Celery Documentation

tmux new -s python-sesh

source celeryflask-env/bin/activate

python backend.py

tmux new -s celery-sesh

source celeryflask-env/bin/activate

celery -A app_and_tasks worker --loglevel INFO

create_celery_flask.py

from flask import Flask
from celery import Celery, Task

def create_app() -> Flask:
    app = Flask(__name__)
    app.config.from_mapping(
        CELERY=dict(
            broker_url="redis://localhost",
            result_backend="redis://localhost",
            task_ignore_result=True,
        ),
    )
    app.config.from_prefixed_env()
    celery_init_app(app)
    return app

def celery_init_app(app: Flask) -> Celery:
    class FlaskTask(Task):
        def __call__(self, *args: object, **kwargs: object) -> object:
            with app.app_context():
                return self.run(*args, **kwargs)

    celery_app = Celery(app.name, task_cls=FlaskTask)
    celery_app.config_from_object(app.config["CELERY"])
    celery_app.set_default()
    app.extensions["celery"] = celery_app
    return celery_app

app_and_tasks.py

from create_celery_flask import create_app
from flask_cors import CORS
from celery import shared_task
import feedparser

flask_app = create_app()
CORS(flask_app)
celery_app = flask_app.extensions["celery"]

@shared_task(ignore_result=False)
def getpod(url):
    result = feedparser.parse(url)
    return result.feed

backend.py

from flask import request
from celery.result import AsyncResult
from app_and_tasks import flask_app, getpod

@flask_app.post('/startpodreq')
def startpodreq():
    request_data = request.get_json()
    task = getpod.apply_async(args=[request_data['url']])
    return {"task_id": task.id}

# todo: set to this machine's ip when done developing?
if __name__ == "__main__":
    flask_app.run(host='0.0.0.0', debug=True, port=5004)