Celery task always PENDING

Question

I try to run Celery example on Windows with redis backend. The code looks like:

from celery import Celery

app = Celery('risktools.distributed.celery_tasks',
             backend='redis://localhost',
             broker='redis://localhost')

@app.task(ignore_result=False)
def add(x, y):
    return x + y

@app.task(ignore_result=False)
def add_2(x, y):
    return x + y

I start the tasks using iPython console:

>>> result_1 = add.delay(1, 2)    
>>> result_1.state
'PENDING'
>>> result_2 = add_2.delay(2, 3)    
>>> result_2.state
'PENDING'

It seems that both tasks were not executed, but Celery worker output shows that they succeeded:

[2014-12-08 15:00:09,262: INFO/MainProcess] Received task: risktools.distributed.celery_tasks.add[01dedca1-2db2-48df-a4d6-2f06fe285e45]
[2014-12-08 15:00:09,267: INFO/MainProcess] Task celery_tasks.add[01dedca1-2db2-48df-a4d6-2f06fe28
5e45] succeeded in 0.0019998550415s: 3
[2014-12-08 15:00:24,219: INFO/MainProcess] Received task: risktools.distributed.celery_tasks.add[cb5505ce-cf93-4f5e-aebb-9b2d98a11320]
[2014-12-08 15:00:24,230: INFO/MainProcess] Task celery_tasks.add[cb5505ce-cf93-4f5e-aebb-9b2d98a1
1320] succeeded in 0.010999917984s: 5

I've tried to troubleshoot this issue according to Celery documentation, but none of the advices were useful. What am I doing wrong and how can I receive results from a Celery task?

UPD: I've added a task without ignore_result parameter, but nothing has changed

@app.task
def add_3(x, y):
    return x + y

>>>r = add_3.delay(2, 2)
>>>r.state
'PENDING'

Solution 1

According to Celery 'Getting Started' not able to retrieve results; always pending and https://github.com/celery/celery/issues/2146 it is a Windows issue. Celery --pool=solo option solves the issue.

Solution 2

Instead of Celery --pool=solo option, try -P threads on Windows.

Solution 3

Setting CELERY_TASK_TRACK_STARTED = True (or track_started=True on individual tasks) can also help - this will enable the STARTED status.

Solution 4

Remove the ignore_result=False from the celery docs

Task.ignore_result

Don’t store task state. Note that this means you can’t 
use AsyncResult to check if the task is ready, or get its return value.

Solution 5

thanks everyone.

my celery config:

-------------- celery@DESKTOP-FD38GOO v4.4.2 (cliffs)
--- ***** -----
-- ******* ---- Windows-10-10.0.18362-SP0 2020-04-17 06:58:18
- *** --- * ---
- ** ---------- [config]
- ** ---------- .> app:         mysite:0x25cfd40d208
- ** ---------- .> transport:   redis://localhost:6379//
- ** ---------- .> results:     redis://localhost:6379/1
- *** --- * --- .> concurrency: 8 (thread)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery


[tasks]
  . mysite.celery.debug_task
  . supplier.tasks.add
  . supplier.tasks.count_widgets
  . supplier.tasks.count_widgets2
  . supplier.tasks.mul
  . supplier.tasks.xsum

i have fixed such issue:

i pending such issue about 1 days, and try uninstall redis and install redis on windows 10 some times.

at last i found there are not concurrency config.

first solution:

celery -A mysite worker -l info -P threads

second solution:

celery -A mysite worker -l info --pool=solo

my celery config:

CELERY_BROKER_URL = 'redis://localhost:6379'
CELERY_RESULT_BACKEND = 'redis://localhost:6379/1'
CELERY_ACCEPT_CONTENT = ['application/json']
CELERY_RESULT_SERIALIZER = 'json'
CELERY_TASK_SERIALIZER = 'json'
CELERY_IGNORE_RESULT = False
CELERY_TIMEZONE = TIME_ZONE
CELERY_TRACK_STARTED = True
CELERYD_LOG_FILE = os.path.join(
    BASE_DIR, 'celery', 'logs')   
CELERYD_LOG_LEVEL = "INFO"

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Comments

[Ivan Gromov]

I still get PENDING state (see add_3 method in UPD)

[xxmajia]

Mac also encounters this issue as well, thanks for the tips

[Yan Sklyarenko]

This sounds like a comment, not an answer.