Celery raises ValueError: not enough values to unpack

Question

Trying to run simple example with Celery and receiving an exception. RabbitMQ started in a Docker, also tried to start it locally. Celery works on a local Windows host

from celery import Celery

app = Celery('tasks', broker='amqp://192.168.99.100:32774')

@app.task()
def hello():
    print('hello')


if __name__ == '__main__':
    hello.delay()

Excerpt of my error text:

[2017-08-18 00:01:08,632: ERROR/MainProcess] Task handler raised error: ValueError('not enough values to unpack (expected 3, got 0)',)
Traceback (most recent call last):                                              
    File "c:\users\user\celenv\lib\site-packages\billiard\pool.py", line 358, in workloop                        
        result = (True, prepare_result(fun(*args, **kwargs)))                                  
    File "c:\users\user\celenv\lib\site-packages\celery\app\trace.py", line 525, in _fast_trace_task
        tasks, accept, hostname = _loc
ValueError: not enough values to unpack (expected 3, got 0)

which celery version? as far as I remember celery doesn't supported in windows since celery 4 — ItayB, Aug 19 '17 at 16:37
@ItayB Thank you! I've found that the problem exactly in celery on windows, but I didn't know this about version 4. I've used 4.1.0. — Igor Nikolaev, Aug 20 '17 at 17:59

score 94 · Answer 1 · edited Feb 01 '19 at 15:02

Celery 4.0+ does not officially support Windows yet. But it still works on Windows for some development/test purposes.

Use eventlet instead as below:

pip install eventlet
celery -A <module> worker -l info -P eventlet

It works for me on Windows 10 + celery 4.1 + python 3.

===== update 2018-11 =====

Eventlet has an issue on subprocess.CalledProcessError:

https://github.com/celery/celery/issues/4063

https://github.com/eventlet/eventlet/issues/357

https://github.com/eventlet/eventlet/issues/413

So try gevent instead.

pip install gevent
celery -A <module> worker -l info -P gevent

This works for me on Windows 10 + celery 4.2 + python 3.6

I tried running with `-l info -c 5 gevent` flags and got `unrecognized arguments: gevent`. It however works with `-l info -P gevent`. How can I fix this? — Azima, May 09 '20 at 07:59

score 18 · Answer 2 · answered Jul 21 '20 at 08:41

18

It worked for me:

celery -A my_project_name worker --pool=solo -l info

basically things become single threaded and are suppoted

answered Jul 21 '20 at 08:41

nofoobar

2,826
20
24

2

It's still working in Nov 29th, 2022. Thanks. – Super Kai - Kazuya Ito Nov 28 '22 at 20:29

score 17 · Answer 3 · answered Oct 26 '18 at 20:13

17

I got this error on Windows 7 32bit system. So I did this to make it work.

Add this

`os.environ.setdefault('FORKED_BY_MULTIPROCESSING', '1')`

before defining a celery instance in myproj/settings.py file in your django project.

It should like like

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'myproj.settings')
os.environ.setdefault('FORKED_BY_MULTIPROCESSING', '1')

app = Celery('tasks', broker='redis://127.0.0.1:6379/0')

I am using redis as a messaging broker so defined broker='redis://127.0.0.1:6379/0'

answered Oct 26 '18 at 20:13

Lawrence Gandhar

718
8
12

Thanks, this worked for me. Would have spent hours (on top of the ones already spent). I was just trying the example from docs.celeryproject.org: import os os.environ.setdefault('FORKED_BY_MULTIPROCESSING', '1') app = Celery('tasks', broker='amqp://guest@localhost//') etc – Coffee and Code Mar 01 '20 at 14:16

score 12 · Answer 4 · answered May 29 '18 at 12:52

12

For Celery 4.1 on Windows.

Set an environment variable FORKED_BY_MULTIPROCESSING=1. Then you can simply run celery -A <celery module> worker.

answered May 29 '18 at 12:52

Bob Jordan

3,049
2
34
41

score 7 · Accepted Answer · edited May 08 '20 at 07:24

7

Which celery version? As far as I remember celery isn't supported in windows since celery 4

edited May 08 '20 at 07:24

svarog

9,477
4
61
77

answered Aug 20 '17 at 18:00

ItayB

10,377
9
50
77

Gaetan Abio Bamongoyo · Answer 6 · 2022-07-30T08:58:26.003

0

run this command

celery -A name_of_project worker --pool=solo -l info

edited Jul 30 '22 at 08:58

answered Jul 30 '22 at 08:57

Gaetan Abio Bamongoyo

1
2

Celery raises ValueError: not enough values to unpack

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