Celery ValueError: not enough values to unpack (expected 3, got 0)的解决方案

pycharm的Terminal中执行worker启动命令：

D:pythonFiles	est_celery> celery -A celery_app worker --loglevel=info

报错：

 -------------- celery@DESKTOP-0R048UM v4.4.2 (cliffs)
--- ***** -----
-- ******* ---- Windows-10-10.0.18362-SP0 2020-04-07 14:26:56
- *** --- * ---
- ** ---------- [config]
- ** ---------- .> app:         mails:0x18c481036a0
- ** ---------- .> transport:   redis://127.0.0.1:6379//
- ** ---------- .> results:     redis://127.0.0.1:6379/0
- *** --- * --- .> concurrency: 8 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery


[tasks]
  . celery_app.mail_test.send_mail

[2020-04-07 14:26:56,261: INFO/MainProcess] Connected to redis://127.0.0.1:6379//
[2020-04-07 14:26:56,276: INFO/MainProcess] mingle: searching for neighbors
[2020-04-07 14:26:56,915: INFO/SpawnPoolWorker-1] child process 8840 calling self.run()
[2020-04-07 14:26:56,920: INFO/SpawnPoolWorker-2] child process 17180 calling self.run()
[2020-04-07 14:26:56,931: INFO/SpawnPoolWorker-3] child process 5680 calling self.run()
[2020-04-07 14:26:56,941: INFO/SpawnPoolWorker-5] child process 18680 calling self.run()
[2020-04-07 14:26:56,944: INFO/SpawnPoolWorker-7] child process 21336 calling self.run()
[2020-04-07 14:26:56,949: INFO/SpawnPoolWorker-6] child process 3484 calling self.run()
[2020-04-07 14:26:56,960: INFO/SpawnPoolWorker-4] child process 13028 calling self.run()
[2020-04-07 14:26:56,972: INFO/SpawnPoolWorker-8] child process 3128 calling self.run()
[2020-04-07 14:26:57,313: INFO/MainProcess] mingle: all alone
[2020-04-07 14:26:57,362: INFO/MainProcess] celery@DESKTOP-0R048UM ready.
[2020-04-07 14:27:03,003: INFO/MainProcess] Received task: celery_app.mail_test.send_mail[3f2aff1a-0555-497e-aaef-a28c184ec1fe]
[2020-04-07 14:27:03,007: ERROR/MainProcess] Task handler raised error: ValueError('not enough values to unpack (expected 3, got 0)',)
Traceback (most recent call last):
  File "d:python3.6.4libsite-packagesilliardpool.py", line 362, in workloop
    result = (True, prepare_result(fun(*args, **kwargs)))
  File "d:python3.6.4libsite-packagesceleryapp	race.py", line 546, in _fast_trace_task
    tasks, accept, hostname = _loc
ValueError: not enough values to unpack (expected 3, got 0)

网上找了一些之后，发现：https://www.cnblogs.com/Hannibal-2018/p/11147224.html  ，参照这个大兄弟的解决方法------安装eventlet

pip install eventlet

再次执行任务则没有报错(需要加上 -P eventlet参数)：

D:pythonFiles	est_celery> celery -A celery_app worker --loglevel=info -P eventlet

 -------------- celery@DESKTOP-0R048UM v4.4.2 (cliffs)
--- ***** -----
-- ******* ---- Windows-10-10.0.18362-SP0 2020-04-07 14:28:41
- *** --- * ---
- ** ---------- [config]
- ** ---------- .> app:         mails:0x1e9cb8556a0
- ** ---------- .> transport:   redis://127.0.0.1:6379//
- ** ---------- .> results:     redis://127.0.0.1:6379/0
- *** --- * --- .> concurrency: 8 (eventlet)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery


[tasks]
  . celery_app.mail_test.send_mail

[2020-04-07 14:28:41,149: INFO/MainProcess] Connected to redis://127.0.0.1:6379//
[2020-04-07 14:28:41,167: INFO/MainProcess] mingle: searching for neighbors
[2020-04-07 14:28:42,189: INFO/MainProcess] mingle: all alone
[2020-04-07 14:28:42,204: INFO/MainProcess] pidbox: Connected to redis://127.0.0.1:6379//.
[2020-04-07 14:28:42,207: INFO/MainProcess] celery@DESKTOP-0R048UM ready.
[2020-04-07 14:28:47,919: INFO/MainProcess] Received task: celery_app.mail_test.send_mail[9c1fcca3-04ec-4d34-b9e6-4c3026283d79]

参考：https://www.cnblogs.com/Hannibal-2018/p/11147224.html