BUG——Celery ValueError: not enough values to unpack

背景

最近因项目需要，学习任务队列Celery的用法，跟着官网写Demo，出现如题错误，最终在github的Issues里找到解决办法，记录如下。

场景还原

本地环境如下：

• Windows 7
• Python 3.6.7
• Celery 4.1.0

代码tasks.py：

from celery import Celery

app = Celery('tasks', broker='redis://:xxxx@xxx.xxx.xxx.xx:6379/0')

@app.task
def add(x, y):
    return x + y

执行worker

celery -A tasks worker --loglevel=info

输出：

 -------------- celery@YG_lin v4.2.1 (windowlicker)
---- **** -----
--- * ***  * -- Windows-7-6.1.7601-SP1 2018-12-05 20:03:58
-- * - **** ---
- ** ---------- [config]
- ** ---------- .> app:         tasks:0x38527b8
- ** ---------- .> transport:   redis://:**@192.168.0.2:6379//
- ** ---------- .> results:     redis://:**@192.168.0.2:6379/1
- *** --- * --- .> concurrency: 4 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery

[tasks]
  . tasks.add

[2018-12-05 20:03:58,721: INFO/MainProcess] Connected to redis://:**@192.168.0.2:6379//
[2018-12-05 20:03:58,735: INFO/MainProcess] mingle: searching for neighbors
[2018-12-05 20:03:58,976: INFO/SpawnPoolWorker-1] child process 16292 calling self.run()
[2018-12-05 20:03:59,006: INFO/SpawnPoolWorker-2] child process 14764 calling self.run()
[2018-12-05 20:03:59,026: INFO/SpawnPoolWorker-3] child process 13864 calling self.run()
[2018-12-05 20:03:59,078: INFO/SpawnPoolWorker-4] child process 15980 calling self.run()
[2018-12-05 20:03:59,893: INFO/MainProcess] mingle: all alone
[2018-12-05 20:03:59,915: INFO/MainProcess] celery@YG_lin ready.

打开另一个python终端：

>>>from tasks import add
>>>add.delay(4, 4)

然后worker里报错：

[2018-12-05 20:03:59,933: ERROR/MainProcess] Task handler raised error: ValueError('not enough values to unpack (expected 3, got 0)',)
Traceback (most recent call last):
  File "c:\users\administrator\envs\dj11.7\lib\site-packages\billiard\pool.py", line 358, in workloop
    result = (True, prepare_result(fun(*args, **kwargs)))
  File "c:\users\administrator\envs\dj11.7\lib\site-packages\celery\app\trace.py", line 537, in _fast_trace_task
    tasks, accept, hostname = _loc
ValueError: not enough values to unpack (expected 3, got 0)
[2018-12-05 20:04:15,392: INFO/MainProcess] Received task: tasks.add[b76c9d02-ca3c-4272-b593-89c280f633da]
[2018-12-05 20:04:15,399: ERROR/MainProcess] Task handler raised error: ValueError('not enough values to unpack (expected 3, got 0)',)
Traceback (most recent call last):
  File "c:\users\administrator\envs\dj11.7\lib\site-packages\billiard\pool.py", line 358, in workloop
    result = (True, prepare_result(fun(*args, **kwargs)))
  File "c:\users\administrator\envs\dj11.7\lib\site-packages\celery\app\trace.py", line 537, in _fast_trace_task
    tasks, accept, hostname = _loc
ValueError: not enough values to unpack (expected 3, got 0

解决：

看别人描述大概就是说win10上运行celery4.x就会出现这个问题，解决办法如下,原理未知：

先安装一个eventlet

pip install eventlet

然后启动worker的时候加一个参数，如下：

celery -A <mymodule> worker -l info -P eventlet

也就是

celery -A tasks worker -l info -P eventlet

然后就可以正常的调用了。