Cannot add link to group: do that on individual tasks

Package:

celery

17847

Exception Class:

TypeError

Raise code

ly_async(self, args=None, kwargs=None, add_to_parent=True,
                    producer=None, link=None, link_error=None, **options):
        args = args if args else ()
        if link is not None:
            raise TypeError('Cannot add link to group: use a chord')
        if link_error is not None:
            raise TypeError(
                'Cannot add link to group: do that on individual tasks')
        app = self.app
        if app.conf.task_always_eager:
            return self.apply(args, kwargs, **options)
        if not self.tasks:
            return self.freeze()

        opti

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Links to the raise (1)

https://github.com/celery/celery/blob/fc57a612c07c8121ad6606a20641e4da35de00b3/celery/canvas.py#L1078

Ways to fix

Error code:

from celery import canvas 

#Create Signatures 
s = canvas.signature('tasks.add', args=(2, 2))
b = canvas.signature('tasks.add', args=(4,4))
#Creates a group of tasks
lazy_group = canvas.group([s, b])

lazy_group.apply_async(link_error='link of error')

Summary:

The exception is thrown in the apply_async method when calling the Group class which creates a group of tasks to be executed in parallel.

So that, when apply_async is called with parameter link_error, it will throw an error.

if link_error is not None:
  raise TypeError(
      'Cannot add link to group: do that on individual tasks')

Fix code:

from celery import canvas 

#Create Signatures 
s = canvas.signature('tasks.add', args=(2, 2))
b = canvas.signature('tasks.add', args=(4,4))
#Creates a group of tasks
lazy_group = canvas.group([s, b])

lazy_group.apply_async()

Jul 27, 2021

anonim 13.0k

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