Celery Error 111 Connection refused (tested)

Celery raises kombu.exceptions.OperationalError: Error 111 ... Connection refused when delay() cannot reach the broker. Either Redis/RabbitMQ is not running at that address, or Celery is using its default amqp://localhost:5672 broker because your setting was not read.

1. Reproduce it: delay() with the broker down

import time
from celery import Celery
app = Celery('tasks', broker='redis://localhost:6379/0')
@app.task
def add(x, y):
    return x + y
t = time.monotonic()
try:
    add.delay(2, 3)
except Exception as e:
    print(f'{type(e).__module__}.{type(e).__name__}: {e}')
print(f'after {time.monotonic() - t:.1f}s')

Output:

kombu.exceptions.OperationalError: Error 111 connecting to localhost:6379. Connection refused.
after 0.9s

No Redis is listening on localhost:6379, so delay() retries the publish and then raises kombu.exceptions.OperationalError: Error 111 connecting to localhost:6379. Connection refused. Errno 111 is the OS-level ECONNREFUSED: the host answered, but nothing accepts connections on that port. The task never reaches a worker.

2. Fail fast instead of retrying

import time
from celery import Celery
app = Celery('tasks', broker='redis://localhost:6379/0')
@app.task
def add(x, y):
    return x + y
t = time.monotonic()
try:
    add.apply_async((2, 3), retry_policy={'max_retries': 1, 'interval_start': 0})
except Exception as e:
    print(f'{type(e).__name__}: {e}')
print(f'after {time.monotonic() - t:.1f}s')

Output:

OperationalError: Error 111 connecting to localhost:6379. Connection refused.
after 0.1s

retry_policy on apply_async() controls the publish retries (here 0.9 s by default, 0.1 s with one retry and no wait). Catch kombu.exceptions.OperationalError around delay() in a web view if a broker outage should not turn into a 500 for the user.

3. "[Errno 111]" on port 5672: Celery is not reading your broker setting

from celery import Celery
class settings:                       # stands in for Django settings
    BROKER_URL = 'redis://localhost:6379/0'          # wrong name for namespace='CELERY'
app = Celery('proj')
app.config_from_object(settings, namespace='CELERY')
print('broker used:', app.connection_for_write().as_uri())
@app.task
def add(x, y):
    return x + y
try:
    add.apply_async((2, 3), retry_policy={'max_retries': 0})
except Exception as e:
    print(f'{type(e).__name__}: {e}')
class settings:
    CELERY_BROKER_URL = 'redis://localhost:6379/0'   # matches the namespace
app2 = Celery('proj')
app2.config_from_object(settings, namespace='CELERY')
print('broker used:', app2.connection_for_write().as_uri())

Output:

broker used: amqp://guest:**@localhost:5672//
OperationalError: [Errno 111] Connection refused
broker used: redis://localhost:6379/0

If the error mentions amqp://guest@localhost:5672 even though you use Redis, Celery fell back to its default RabbitMQ broker because your setting was never read. With app.config_from_object('django.conf:settings', namespace='CELERY'), every setting needs the CELERY_ prefix: CELERY_BROKER_URL, not BROKER_URL. Print app.connection_for_write().as_uri() to see which broker the app actually uses.

4. Checklist

• Is the broker running? redis-cli -h HOST ping should answer PONG.
• In Docker Compose, localhost is the container itself: use the service name, e.g. redis://redis:6379/0.
• Is the setting read? Check the URI printed as in block 3.

Related: Redis connection refused, Python ConnectionRefusedError Errno 111.

Written with AI assistance. Measured on 2026-10-23 with Celery 5.6.3, kombu 5.6.2 and Python 3.14.7 (python:3-alpine in Docker, no broker running). Each block was run verbatim and the output pasted unedited. PlainHeaders is our extension; Python and Celery are free.