芹菜异常处理

Question

假设我有这个任务定义：

def some_other_foo(input)
raise Exception('This is not handled!')
return input

@app.task(
  bind=True,
  max_retries=5,
  soft_time_limit=20)
def some_foo(self, someInput={}):
   response=""
   try:
     response = some_other_foo(someInput)
   except Exception as exc:
     self.retry(countdown=5, exc=exc)
     response="error"
 return response

我有一个问题，即 some_foo 中未处理异常，我得到错误而不是 response="error"，任务崩溃，我得到 Traceback，表明引发了异常。

是否可以返回常规响应，但将芹菜任务设置为失败，因此结果花将失败？

我正在使用：
Celery 4.1
AMPQ 作为代理
Celery Flower 作为监控

Answer 1

Try \ except工作正常。你的任务总是不成功，因为你self.retry之前调用过return。让我们做一个小测试：

from celery import Celery

app = Celery(name_app,broker_settings_etc....)

def some_other_foo(value):
    raise Exception('This is not handled!')

@app.task(
  bind=True,
  max_retries=5,
  soft_time_limit=20)
def some_foo(self):
    response = ""

    try:
        response = some_other_foo('test')
    except Exception as exc:
        self.retry(countdown=5, exc=exc)
        response = "error"

    return response

运行 celery 应用程序并调用我们的任务。您将在 celery 日志中看到如下内容：

3fb-81de-e4149fa88f4c] retry: Retry in 5s: Exception('This is not handled!',)
[2017-08-18 15:50:34,160: INFO/MainProcess] Received task: tasks.some_foo[b656731b-c85d-43fb-81de-e4149fa88f4c] eta:[2017-08-18 12:50:39.156912+00:00]
[2017-08-18 15:50:34,161: INFO/MainProcess] Task tasks.some_foo[b656731b-c85d-43fb-81de-e4149fa88f4c] retry: Retry in 5s: Exception('This is not handled!',)
[2017-08-18 15:50:39,511: ERROR/MainProcess] Task tasks.some_foo[b656731b-c85d-43fb-81de-e4149fa88f4c] raised unexpected: Exception('This is not handled!',)
Traceback (most recent call last): 
# trace here...
Exception: This is not handled!

这个怎么运作。你为任务设置max_retries=5。当您调用self.retry(countdown=5, exc=exc)Celery 时会中断任务处理并尝试使用countdown（在我们的示例中 = 5）重新启动任务。5 次尝试后( max_retries) Celery 不会重新运行任务。

现在，让我们将try \ except块更改为：

try:
    response = some_other_foo('test')
except Exception:
    print 'handled'
    response = "bad response"

重启 Celery 并运行我们的任务。让我们检查日志：

[2017-08-18 15:58:41,893: INFO/MainProcess] Received task: tasks.some_foo[1437e7ce-1c69-4042-824b-5602f486c025]
[2017-08-18 15:58:41,895: WARNING/Worker-3] handled
[2017-08-18 15:58:41,896: INFO/MainProcess] Task tasks.some_foo[1437e7ce-1c69-4042-824b-5602f486c025] succeeded in 0.00186271299026s: 'bad response'

如您所见，处理程序工作正常。

所以，总结一下。如果调用self.retry，Celery 将中断任务处理并尝试重新启动当前任务。