Heroku Celery - Connection Refused-CodePudding

I have a Flask application deployed on Heroku. I'm trying to set up Celery using Redis as the message broker.

This error comes up in heroku logs:

2021-10-16T15:08:12.851586 00:00 app[worker.1]: [2021-10-16 15:08:12,851: ERROR/MainProcess] consumer: Cannot connect to amqp://guest:**@127.0.0.1:5672//: [Errno 111] Connection refused.

Procfile: worker: celery -A my_app.celery worker --loglevel=debug

The Heroku Redis add-on is installed, and I used this command to start a dyno: heroku ps:scale worker=1

app/__init__.py

...
from extensions import celery

...

def create_app(config_class=Config):
    app = Flask(__name__)
    app.config.from_object(Config)

    ...

    celery.init_app(app)

app/extensions.py

import flask
from celery import Celery

class FlaskCelery(Celery):
    def __init__(self, *args, **kwargs):

        super(FlaskCelery, self).__init__(*args, **kwargs)
        self.patch_task()

        if 'app' in kwargs:
            self.init_app(kwargs['app'])

    def patch_task(self):
        TaskBase = self.Task
        _celery = self

        class ContextTask(TaskBase):
            abstract = True

            def __call__(self, *args, **kwargs):
                if flask.has_app_context():
                    return TaskBase.__call__(self, *args, **kwargs)
                else:
                    with _celery.app.app_context():
                        return TaskBase.__call__(self, *args, **kwargs)

        self.Task = ContextTask

    def init_app(self, app):
        self.app = app
        self.config_from_object(app.config)


celery = FlaskCelery()

config.py

class Config(object):
    ...
    
    CELERY_BROKER_URL = os.environ.get('REDIS_URL') or 'redis://localhost:6379/0'
    CELERY_BACKEND_URL = os.environ.get('REDIS_URL') or 'redis://localhost:6379/0'
    ...

I'm wondering if maybe I'm using the wrong command in the Procfile. The Heroku documentation recommends using worker: celery worker --app=tasks.app, but this produces an error saying the syntax is outdated. The command I'm using is the same one I run locally to start a celery worker

I also tried to manually set the broker and backend urls to the Heroku Redis url redis://:p8... .amazonaws.com:1..., but I received the same error.

CodePudding user response：

Changing the config variables fixes this issue:

CELERY_BROKER_URL -> BROKER_URL

CELERY_BACKEND_URL -> CELERY_RESULT_BACKEND

This is described in the Heroku Documentation

However, it's the case that these config variables are not updated per the Celery documentation. There, it's recommended to use broker_url and result_backend, and you'll receive a deprecation warning using the other variable names.