Issue 1:
Using the method described at http://docs.celeryproject.org/en/latest/userguide/workers.html#pool-restart-command only restart 1 process in the worker's process pool but not all. The other processes may restart only after the worker received other tasks. How can I make sure all the processes of the worker are restarted?

For example, using tasks defined in this gist https://gist.github.com/lebinh/165f7edb95daa08bee54 and start a worker with concurrency 2: celery -A tasks worker -l info -c 2. After sending pool_restart command with tasks.app.control.broadcast('pool_restart') I got this log:

[2014-06-05 18:53:43,310: WARNING/Worker-1] worker process shutdown
[2014-06-05 18:53:44,350: WARNING/Worker-3] worker process init
^C
worker: Hitting Ctrl+C again will terminate all running tasks!

worker: Warm shutdown (MainProcess)
[2014-06-05 18:54:05,368: WARNING/Worker-2] worker process shutdown
[2014-06-05 18:54:05,368: WARNING/Worker-3] worker process shutdown

The worker process 1 is restarted but worker process 2 is still there until I terminate the worker.

I'm using the latest version of Celery, 3.1.11 (Cipater), on Ubuntu 14.04 running on EC2.

Issue 2:
Checklist

I have verified that the issue exists against the master branch of Celery.

This has already been asked to the discussion group 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 master branch.

I have included all related issues and possible duplicate issues

in this issue (If there are none, check this box anyway).

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 master 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

https://groups.google.com/g/celery-users/c/3Z07zPfUZQ0/m/VpOCC2PGDQAJ

(semi-related but different) #6690

Possible Duplicates

None

Environment & Settings

Celery version: 5.1.1

celery report Output:

(celery_movies) C:\Users\markb\PycharmProjects\celery_movies>celery -A celery_movies report

software -> celery:5.1.1 (sun-harmonics) kombu:5.1.0 py:3.7.2

billiard:3.6.4.0 py-amqp:5.0.6

platform -> system:Windows arch:32bit, WindowsPE

kernel version:10 imp:CPython

loader -> celery.loaders.app.AppLoader

settings -> transport:amqp results:file:///C:/Users/markb/tmp

Exchange: <class 'kombu.entity.Exchange'>

Queue: <class 'kombu.entity.Queue'>

imports: ['celery_movies.tasks']

task_acks_late: True

task_default_exchange: 'my_exchange'

task_queues: [<unbound Queue movies -> <unbound Exchange my_exchange(direct)> -> movies>]

task_routes: {

'movies.': {'queue': 'movies'}, 'news.': {'queue': 'news'}}

deprecated_settings: None

broker_url: 'amqp://guest:********@localhost:5672//'

result_backend: 'file:///C:/Users/markb/tmp'

(celery_news) C:\Users\markb\PycharmProjects\celery_news>celery -A celery_news report

software -> celery:5.1.1 (sun-harmonics) kombu:5.1.0 py:3.7.2

billiard:3.6.4.0 py-amqp:5.0.6

platform -> system:Windows arch:32bit, WindowsPE

kernel version:10 imp:CPython

loader -> celery.loaders.app.AppLoader

settings -> transport:amqp results:file:///C:/Users/markb/tmp

Exchange: <class 'kombu.entity.Exchange'>

Queue: <class 'kombu.entity.Queue'>

imports: ['celery_news.tasks']

task_acks_late: True

task_default_exchange: 'my_exchange'

task_queues: [<unbound Queue news -> <unbound Exchange my_exchange(direct)> -> news>,

<unbound Queue celery -> <unbound Exchange my_exchange(direct)> -> celery>]

task_routes: {

'movies.': {'queue': 'movies'}, 'news.': {'queue': 'news'}}

deprecated_settings: None

broker_url: 'amqp://guest:********@localhost:5672//'

result_backend: 'file:///C:/Users/markb/tmp'

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

amqp==5.0.6
billiard==3.6.4.0
cached-property==1.5.2
celery==5.1.1
click==7.1.2
click-didyoumean==0.0.3
click-plugins==1.1.1
click-repl==0.2.0
importlib-metadata==4.6.1
kombu==5.1.0
prompt-toolkit==3.0.19
pytz==2021.1
six==1.16.0
typing-extensions==3.10.0.0
vine==5.0.0
wcwidth==0.2.5
zipp==3.5.0

Minimally Reproducible Test Case

Worker #1
celery.py (launched via: celery -A celery_movies worker -l info --pool=solo)

from celery.app import Celery
from celery_movies import celeryconfig

broker_url = 'amqp://'
celery_app = Celery('movies')
celery_app.config_from_object(celeryconfig)
celery_app.conf.update(broker_url=broker_url,
result_backend="file:///C:/Users/markb/tmp")

celeryconfig.py

from kombu.common import Queue, Exchange

imports = ['celery_movies.tasks']
task_acks_late = True
task_default_exchange = "my_exchange"

task_queues = [Queue('movies', exchange=Exchange(name=task_default_exchange), routing_key='movies')
]

task_routes = {
'movies.*': {'queue': 'movies'},
'news.*': {'queue': 'news'}
}

tasks.py

from celery_movies.celery import celery_app

@celery_app.task(name='movies.task.publish_movie', bind=True)
def publish_movie(self, *args, **kwargs):
print("publishing movie")

Worker #2

celery.py (launched via: celery -A celery_news worker -l info --pool=solo)

from celery.app import Celery
from celery_news import celeryconfig

broker_url = 'amqp://'
celery_app = Celery('news')
celery_app.config_from_object(celeryconfig)
celery_app.conf.update(broker_url=broker_url,
result_backend="file:///C:/Users/markb/tmp")

celeryconfig.py

from kombu.common import Queue, Exchange

imports = ['celery_news.tasks']
task_acks_late = True
task_default_exchange = "my_exchange"

task_queues = [Queue('news', exchange=Exchange(name=task_default_exchange), routing_key='news'),
Queue('celery', exchange=Exchange(name=task_default_exchange), routing_key='celery')]

task_routes = {
'movies.*': {'queue': 'movies'},
'news.*': {'queue': 'news'}
}

tasks.py

from celery_news.celery import celery_app

@celery_app.task(name='news.task.publish_news', bind=True)
def publish_news(self, *args, **kwargs):
print("publishing news")

trigger_flow.py

from celery import group, chain
import uuid
from celery.app import Celery
from celery_movies import celeryconfig

broker_url = 'amqp://'
celery_app = Celery('movies')
celery_app.config_from_object(celeryconfig)
celery_app.conf.update(broker_url=broker_url,
result_backend="file:///C:/Users/markb/tmp")

movie_task = celery_app.signature('movies.task.publish_movie', task_id=str(uuid.uuid4()), immutable=True)
news_task = celery_app.signature('news.task.publish_news', task_id=str(uuid.uuid4()), immutable=True)

my_chord = chain(movie_task,
group(movie_task.set(task_id=str(uuid.uuid4())), movie_task.set(task_id=str(uuid.uuid4()))),
news_task)
my_chord.apply_async()

Expected Behavior

I expect my first task to be handled by the Movies worker, then the chord to start executing the two grouped movie tasks via the Movies worker, and then finally the News worker should pick up and execute the news task

Actual Behavior

First task is handled by the Movies worker, but when the Movies worker tries to move on to the Chord (Group + Chain was upgraded to Chord), system chunks on attempting to submit the chord_unlock task.

[2021-07-07 20:01:48,298: WARNING/MainProcess] C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\app\trace.py:659: RuntimeWarning: Exception raised outside body: Task of kind 'news.task.publish_news' never registered, please make sure it's imported.:
Traceback (most recent call last):
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\cached_property.py", line 70, in __get__
return obj_dict[name]
KeyError: 'type'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\app\trace.py", line 515, in trace_task
priority=task_priority
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\canvas.py", line 1416, in apply_async
return self.run(tasks, body, args, task_id=task_id, **merged_options)
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\canvas.py", line 1488, in run
max_retries=max_retries,
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\backends\base.py", line 657, in apply_chord
self.fallback_chord_unlock(header_result, body, **kwargs)
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\backends\base.py", line 642, in fallback_chord_unlock
queue = body.options.get('queue', getattr(body.type, 'queue', None))
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\kombu\utils\objects.py", line 29, in __get__
return super().__get__(instance, owner)
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\cached_property.py", line 74, in __get__
return obj_dict.setdefault(name, self.func(obj))
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\canvas.py", line 498, in type
return self._type or self.app.tasks[self['task']]
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\app\registry.py", line 18, in __missing__
raise self.NotRegistered(key)
celery.exceptions.NotRegistered: 'news.task.publish_news'

exc, exc_info.traceback)))

[2021-07-07 20:01:48,300: ERROR/MainProcess] Task movies.task.publish_movie[f734ecc4-d174-41c3-b0dd-96544b9815a3] raised unexpected: Task of kind 'news.task.publish_news' never registered, please make sure it's imported.
Traceback (most recent call last):
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\cached_property.py", line 70, in __get__
return obj_dict[name]
KeyError: 'type'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\app\trace.py", line 515, in trace_task
priority=task_priority
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\canvas.py", line 1416, in apply_async
return self.run(tasks, body, args, task_id=task_id, **merged_options)
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\canvas.py", line 1488, in run
max_retries=max_retries,
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\backends\base.py", line 657, in apply_chord
self.fallback_chord_unlock(header_result, body, **kwargs)
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\backends\base.py", line 642, in fallback_chord_unlock
queue = body.options.get('queue', getattr(body.type, 'queue', None))
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\kombu\utils\objects.py", line 29, in __get__
return super().__get__(instance, owner)
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\cached_property.py", line 74, in __get__
return obj_dict.setdefault(name, self.func(obj))
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\canvas.py", line 498, in type
return self._type or self.app.tasks[self['task']]
File "C:\Users\markb\.virtualenvs\celery_movies\lib\site-packages\celery\app\registry.py", line 18, in __missing__
raise self.NotRegistered(key)
celery.exceptions.NotRegistered: 'news.task.publish_news'

This is because the task signatures have no body.type attribute set so a KeyError ends up being thrown when executing the queue = line (and the priority = line)

def fallback_chord_unlock(self, header_result, body, countdown=1,
**kwargs):
kwargs['result'] = [r.as_tuple() for r in header_result]
queue = body.options.get('queue', getattr(body.type, 'queue', None))
priority = body.options.get('priority', getattr(body.type, 'priority', 0))
self.app.tasks['celery.chord_unlock'].apply_async(
(header_result.id, body,), kwargs,
countdown=countdown,
queue=queue,
priority=priority,
)

I believe a solution could be the following, but i'm not confident this doesnt impact something else in Celery

def fallback_chord_unlock(self, header_result, body, countdown=1,
**kwargs):
kwargs['result'] = [r.as_tuple() for r in header_result]
body_type = body.get('type', None)
queue = body.options.get('queue', getattr(body_type, 'queue', None))
priority = body.options.get('priority', getattr(body_type, 'priority', 0))
self.app.tasks['celery.chord_unlock'].apply_async(
(header_result.id, body,), kwargs,
countdown=countdown,
queue=queue,
priority=priority,
)