Everytime I call my api endpoint that uses Celery, I get: ERROR:celery.backends.redis:Connection to Redis lost: Retry (0/20) now.

I don't understand because everything works on my local machine, but not on Heroku.

I have configured the REDIS_URL environment variable and tested that the AWS redis host also works on my local machine.

I can't figure out what the problem is.

Also, when I push my code to Heroku, I see this in the logs: Connected to rediss://:**@ec2-34-194-16-21pute-1.amazonaws:11930//

but when I call my endpoint I get this ERROR:celery.backends.redis:Connection to Redis lost: Retry (0/20) now.

Here is a code snippet.

celery_app.py

from celery import Celery
import ssl

def make_celery(app=None):
    celery = Celery(
        app.import_name if app else "celery_app",
        broker=app.config.get('CELERY_BROKER_URL', 'redis://localhost:6379/0') if app else 'redis://localhost:6379/0',
        backend=app.config.get('result_backend', 'redis://localhost:6379/0') if app else 'redis://localhost:6379/0'
    )
    
    if app:
        celery.conf.update(app.config)

    # Configure SSL for broker and backend if using rediss://
    if celery.conf.broker_url.startswith('rediss://'):
        celery.conf.update(
            broker_use_ssl={
                'ssl_cert_reqs': ssl.CERT_NONE # Enforce SSL validation
            }
        )

    if celery.conf.result_backend.startswith('rediss://'):
        celery.conf.update(
            redis_backend_use_ssl={
                'ssl_cert_reqs': ssl.CERT_NONE # Enforce SSL validation
            }
        )

    return celery

app.py

app = Flask(__name__)
app.config['CELERY_BROKER_URL'] = os.getenv('REDIS_URL', 'redis://localhost:6379/0')
app.config['result_backend'] = os.getenv('REDIS_URL', 'redis://localhost:6379/0')

# Initialize Celery with Flask app
celery = make_celery(app)

Everytime I call my api endpoint that uses Celery, I get: ERROR:celery.backends.redis:Connection to Redis lost: Retry (0/20) now.

I don't understand because everything works on my local machine, but not on Heroku.

I have configured the REDIS_URL environment variable and tested that the AWS redis host also works on my local machine.

I can't figure out what the problem is.

Also, when I push my code to Heroku, I see this in the logs: Connected to rediss://:**@ec2-34-194-16-21.compute-1.amazonaws.com:11930//

but when I call my endpoint I get this ERROR:celery.backends.redis:Connection to Redis lost: Retry (0/20) now.

Here is a code snippet.

celery_app.py

from celery import Celery
import ssl

def make_celery(app=None):
    celery = Celery(
        app.import_name if app else "celery_app",
        broker=app.config.get('CELERY_BROKER_URL', 'redis://localhost:6379/0') if app else 'redis://localhost:6379/0',
        backend=app.config.get('result_backend', 'redis://localhost:6379/0') if app else 'redis://localhost:6379/0'
    )
    
    if app:
        celery.conf.update(app.config)

    # Configure SSL for broker and backend if using rediss://
    if celery.conf.broker_url.startswith('rediss://'):
        celery.conf.update(
            broker_use_ssl={
                'ssl_cert_reqs': ssl.CERT_NONE # Enforce SSL validation
            }
        )

    if celery.conf.result_backend.startswith('rediss://'):
        celery.conf.update(
            redis_backend_use_ssl={
                'ssl_cert_reqs': ssl.CERT_NONE # Enforce SSL validation
            }
        )

    return celery

app.py

app = Flask(__name__)
app.config['CELERY_BROKER_URL'] = os.getenv('REDIS_URL', 'redis://localhost:6379/0')
app.config['result_backend'] = os.getenv('REDIS_URL', 'redis://localhost:6379/0')

# Initialize Celery with Flask app
celery = make_celery(app)

• python
• ssl
• heroku
• redis
• celery

1 Answer 1

Heroku Key-Value Store (Redis) is configured to disconnect after 5 minutes of inactivity by default. If this is what you see, the app should be able to try reconnecting when connection is detected lost.