What is the best option for a (Python 3) task queue on Windows now that Celery 4 has dropped Windows support?

Question

We run a Flask site under IIS on Windows, and for out-of-process tasks we use Celery. Celery has given us some problems under Windows, but for now we are satisfied running v

Answer 1

I run Flask with Huey on Windows without any issues, admittedly only for development and testing. For production I use Flask/Huey on Linux servers. Both with the Redis back-end, Flask 0.12 and Huey 1.2.0 .

I use the factory pattern to create a specialised "cut down" version of a Flask app for specific use by Huey tasks. This version doesn't load blueprints or configure Flask-Admin as these aren't required in the Huey tasks.

Example code of __init__.py in app folder. App is a class extending from Flask:

def create_app(settings_override=None):

    app = App('app')

    if settings_override:
        app.config.from_object(settings_override)
    else:
        app.config.from_object(os.environ['APP_SETTINGS'])

    from .ext import configure_extensions
    configure_extensions(app, admin, load_modules=True)

    # REST
    import rest.api_v1
    app.register_blueprint(api_v1_bp, url_prefix='/api/v1')

    #  ... and more suff


def create_huey_app():
    app = App('huey app')

    app.config.from_object(os.environ['APP_SETTINGS'])

    from .ext import configure_extensions
    configure_extensions(app, admin=None, load_modules=False)

    return app

The idea of configure_extensions is taken from Quokka CMS. Examine its app __init__.py and its extensions module to see how this is implemented. Note also how this project too creates a specific app (create_celery_app) for use with the Celery task queue.

Example of tasks.py. Note the use of with app.app_context(): to create the Flask context. Now my functions have access to the extensions such as Flask-Mail, Flask-SqlAlchemy (db, models) etc.

@huey.task()
def generate_transaction_documents_and_email(transaction_id):
    app = create_huey_app()
    with app.app_context():
        reports.generate_transaction_documents_and_email(transaction_id)


@huey.task()
def send_email(subject, recipients, text_body, html_body, attachments=[], cc=[]):
    app = create_huey_app()
    with app.app_context():
        emails.send_email(subject, recipients, text_body, html_body, attachments, cc)


@huey.periodic_task(crontab(minute='30'))
def synchronize_mailing_list():
    app = create_huey_app()
    if app.config['CREATESEND_SYNCHRONIZE']:
        _list_name = app.config['CREATESEND_LIST']
        with app.app_context():
            sync_delete_ar_subscribers(_list_name)
            sync_add_ar_subscribers(_list_name)