为什么AsyncResult在任务完成后返回NoneType？

Question

Problem

AsyncResult returns NoneType for task after it is finished.

Question

How can I get celery task state after it is done?

Description

Below is a code of django view for getting celery task state. I use this view to query task progress from my client app. It works fine, until the task is done. Afterwards AsyncResult returns NoneType each time I call it for my task, and i get the following error:

'NoneType' object has no attribute 'get'

# Celery configuration
celery = Celery('tasks', backend='amqp', broker="amqp://")

# My django view for getting task state    
def GetTaskStatus(request):
    task = AsyncResult(request.body["taskid"], app=celery)
    if task.state == 'PENDING':
        data = {
            'state': task.state,
            'progress': task.info.get("progress", 0)
        }
    elif task.state != 'FAILURE':
        data = {
            'state': task.state,
            'progress': task.info.get("progress", 0)
        }
    else:
        data = {
            'state': task.state,
            'error': "something went wrong",
            'progress': task.info.get("progress", 0)
        }
    response = GetHttpResponseJSON(ResponseCode.OK, data)
    return response

Answer 1

You need to define a result backend. See the tutorial .