Question

在Celery文档中：http://celery.readthedocs.org/en/latest/userguide/canvas.html#chains是如何使用link_error：

的示例

您还可以使用link_error参数添加错误回调：

add.apply_async((2, 2), link_error=log_error.s())
add.subtask((2, 2), link_error=log_error.s())

由于异常只能在使用pickle时序列化错误回调将父任务的id作为参数：

from __future__ import print_function 
import os 
from proj.celery import app

@app.task 
def log_error(task_id):
    result = app.AsyncResult(task_id)
    result.get(propagate=False)  # make sure result written.
    with open(os.path.join('/var/errors', task_id), 'a') as fh:
        print('--\n\n{0} {1} {2}'.format(
            task_id, result.result, result.traceback), file=fh)

但是在这个例子中是bug，因为他们在任务中调用AsuncResult.get导致DEADLOCK和这个日志条目：

/opt/.virtualenvs/spark/lib/python3.4/site-packages/celery/result.py:45: RuntimeWarning: Never call result.get() within a task!
See http://docs.celeryq.org/en/latest/userguide/tasks.html#task-synchronous-subtasks

In Celery 3.2 this will result in an exception being
raised instead of just being a warning.

  warnings.warn(RuntimeWarning(E_WOULDBLOCK))

[2015-06-13 20:30:19,242: WARNING/Worker-4] /opt/.virtualenvs/spark/lib/python3.4/site-packages/celery/result.py:45: RuntimeWarning: Never call result.get() within a task!
See http://docs.celeryq.org/en/latest/userguide/tasks.html#task-synchronous-subtasks

In Celery 3.2 this will result in an exception being
raised instead of just being a warning.

  warnings.warn(RuntimeWarning(E_WOULDBLOCK))

Answer 1

请执行此检查列表以确保配置正常：

CELERY_IGNORE_RESULT必须设为False
CELERY_BACKEND_RESULT，例如'amqp'（对于RabbitMQ）
@task装饰者必须选项ignore_result=True（但您可以创建immutable signatures）

最后一个是正确修改的任务，用于获取结果（allow_join_result）：

from celery.result import allow_join_result

@app.task
def log_error(task_id):
    with allow_join_result():
        result = app.AsyncResult(task_id)
        result.get(propagate=False)  # make sure result written.
        with open(os.path.join('/var/errors', task_id), 'a') as fh:
            print('--\n\n{0} {1} {2}'.format(
                task_id, result.result, result.traceback), file=fh)

注意：在这种result.result的情况下，ZeroDivisionError是字典：

{ 'exc_type': 'ZeroDivisionError', # Name of Exception type 'exc_message': 'division by zero' # Reason of exception }

注意：

这是#2652问题，当Celery忽略错误时在get()上调用AsyncResult

Celery：如果文档有错误，如何使用“link_error”？

1 个答案:

注意：