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Group result ordering is not respected for groups replacing a task #9909

@simonepozzoli-pix4d

Description

@simonepozzoli-pix4d

Checklist

  • I have verified that the issue exists against the main branch of Celery.
  • This has already been asked to the discussions forum first.
  • I have read the relevant section in the
    contribution guide
    on reporting bugs.
  • I have checked the issues list
    for similar or identical bug reports.
  • I have checked the pull requests list
    for existing proposed fixes.
  • I have checked the commit log
    to find out if the bug was already fixed in the main branch.
  • I have included all related issues and possible duplicate issues
    in this issue (If there are none, check this box anyway).
  • I have tried to reproduce the issue with pytest-celery and added the reproduction script below.

Mandatory Debugging Information

  • I have included the output of celery -A proj report in the issue.
    (if you are not able to do this, then at least specify the Celery
    version affected).
  • I have verified that the issue exists against the main branch of Celery.
  • I have included the contents of pip freeze in the issue.
  • I have included all the versions of all the external dependencies required
    to reproduce this bug.

Optional Debugging Information

  • I have tried reproducing the issue on more than one Python version
    and/or implementation.
  • I have tried reproducing the issue on more than one message broker and/or
    result backend.
  • I have tried reproducing the issue on more than one version of the message
    broker and/or result backend.
  • I have tried reproducing the issue on more than one operating system.
  • I have tried reproducing the issue on more than one workers pool.
  • I have tried reproducing the issue with autoscaling, retries,
    ETA/Countdown & rate limits disabled.
  • I have tried reproducing the issue after downgrading
    and/or upgrading Celery and its dependencies.

Related Issues and Possible Duplicates

Related Issues

  • None

Possible Duplicates

  • None

Environment & Settings

Celery version: 5.5.1

celery report Output:

Steps to Reproduce

Required Dependencies

  • Minimal Python Version: N/A or Unknown
  • Minimal Celery Version: N/A or Unknown
  • Minimal Kombu Version: N/A or Unknown
  • Minimal Broker Version: N/A or Unknown
  • Minimal Result Backend Version: N/A or Unknown
  • Minimal OS and/or Kernel Version: N/A or Unknown
  • Minimal Broker Client Version: N/A or Unknown
  • Minimal Result Backend Client Version: N/A or Unknown

Python Packages

pip freeze Output:

Other Dependencies

Details

N/A

Minimally Reproducible Test Case

Details

from celery import group, shared_task

@shared_task
def add(x, y):
    return x + y

@shared_task(bind=True)
def group_replace(self):
    self.replace(group([add.s(1 ,1), add.s(2, 2)]))


print(group_replace.apply_async().get())  # <- should be [2, 4], sometimes is [4, 2]

Expected Behavior

The order of the group that replaces the task should be maintained, otherwise it's impossible to design a proper canvas.

Actual Behavior

The ordering of the group result is not deterministic

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