python3.7環(huán)境下，安裝了Celery==4.2.0，在啟動celery任務的時候，報錯

根據(jù)Celery官方* Getting Started ?教程，首先創(chuàng)建了一個簡單的tasks任務：
文件名 tasks.py

# coding: utf-8

from celery import Celery
broker = 'redis://127.0.0.1:6379/0'
backend = 'redis://127.0.0.1:6379/0'

app = Celery('tasks', broker=broker, backend=backend)

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

在文件目錄下，命令終端啟動Celery，生產(chǎn)環(huán)境可用supervisor管理，這里只是簡單演示，命令如下

celery -A tasks worker --loglevel=info

第一次我運行的時候報錯了，如下：

File "/Users/li/.venv/venv-myprojet/lib/python3.7/site-packages/celery/backends/redis.py", line 22
    from . import async, base
                      ^
SyntaxError: invalid syntax

搜索了一下錯誤原因，原來是async名稱更換了，如下

[Rename `async` to `asynchronous` (async is a reserved keyword in Python 3.7) #4879](https://github.com/celery/celery/pull/4879)

開發(fā)人員已經(jīng)處理了這個issue，合并了master，快速的解決方案是通過github安裝celery，命令如下：
pip install --upgrade https://github.com/celery/celery/tarball/master

再次運次，那個應該可以看到如下正常輸出：

 -------------- celery@lideMacBook-Pro.local v4.2.0 (windowlicker)
---- **** ----- 
--- * ***  * -- Darwin-16.7.0-x86_64-i386-64bit 2018-07-16 22:50:59
-- * - **** --- 
- ** ---------- [config]
- ** ---------- .> app:         tasksex:0x1110f3a58
- ** ---------- .> transport:   redis://127.0.0.1:6379/0
- ** ---------- .> results:     redis://127.0.0.1:6379/0
- *** --- * --- .> concurrency: 4 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** ----- 
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery
                

[tasks]
  . tasks.add

[2018-07-16 22:50:59,543: INFO/MainProcess] Connected to redis://127.0.0.1:6379/0
[2018-07-16 22:50:59,551: INFO/MainProcess] mingle: searching for neighbors
[2018-07-16 22:51:00,571: INFO/MainProcess] mingle: all alone
[2018-07-16 22:51:00,583: INFO/MainProcess] celery@zhiliangdeMacBook-Pro.local ready.

PS，redis這里選做Celery的broker和backend，如果沒有配置backend，如果不需要處理結果，tasks也是可以正常運行，只是結果沒有存儲的地方，當你調(diào)用ready()函數(shù)的時候，就會報錯，這里應當注意下。

>>> from tasks import add
>>> a=add.delay(1,5)
>>> a
<AsyncResult: 587c76ea-a441-417d-922f-1da860c07762>
>>> a.ready()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/li/.venv/venv-myprojet/lib/python3.7/site-packages/celery/result.py", line 311, in ready
    return self.state in self.backend.READY_STATES
  File "/Users/li/.venv/venv-myprojet/lib/python3.7/site-packages/celery/result.py", line 471, in state
    return self._get_task_meta()['status']
  File "/Users/li/.venv/venv-myprojet/lib/python3.7/site-packages/celery/result.py", line 410, in _get_task_meta
    return self._maybe_set_cache(self.backend.get_task_meta(self.id))
  File "/Users/li/.venv/venv-myprojet/lib/python3.7/site-packages/celery/backends/base.py", line 359, in get_task_meta
    meta = self._get_task_meta_for(task_id)
AttributeError: 'DisabledBackend' object has no attribute '_get_task_meta_for'
>>> 

這里只是需要配置上backend接收處理結果就可以。