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Ensure triggering of callback in chord #397

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Ensure triggering of callback in chord #397

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6e0aa80
Ensure triggering of callback in chord
s-bessing Jul 3, 2023
90344aa
Fixing line length
s-bessing Jul 3, 2023
5c6b5df
Merge branch 'celery:main' into patch-1
s-bessing Apr 30, 2024
1b04c88
update message
Apr 30, 2024
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5 changes: 4 additions & 1 deletion django_celery_results/backends/database.py
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Original file line number Diff line number Diff line change
Expand Up @@ -265,7 +265,6 @@ def on_chord_part_return(self, request, state, result, **kwargs):
else:
# Last task in the chord header has finished
call_callback = True
chord_counter.delete()

if call_callback:
deps = chord_counter.group_result(app=self.app)
Expand All @@ -276,6 +275,10 @@ def on_chord_part_return(self, request, state, result, **kwargs):
callback=callback,
group_result=deps
)
chord_counter.delete()
else:
logger.warning("Chord %s executed more "
"tasks than expected", gid)


def trigger_callback(app, callback, group_result):
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4 changes: 2 additions & 2 deletions t/unit/backends/test_database.py
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Expand Up @@ -862,8 +862,8 @@ def test_on_chord_part_return_failure(self):
request.id = tid2
self.b.mark_as_failure(tid2, ValueError(), request=request)

with pytest.raises(ChordCounter.DoesNotExist):
ChordCounter.objects.get(group_id=gid)
chord_counter.refresh_from_db()
assert chord_counter.count == 1
Comment on lines +865 to +866
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I don't think this is correct, we have a header of 2, 1 is done, the other fails.
If a task in the header fails the chord is done and the callback is not called.

If this is the case, a ChordCounter object will remain in the db for every failed chord.

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@AllexVeldman but if you have retry logic (on code or worker level) all task eventually are successful, but the callback is never triggered.

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https://docs.celeryq.dev/en/latest/reference/celery.result.html#celery.result.AsyncResult.ready would suggest deps.ready() would be False in case of a retry, True in case of a failure like in this test.

So this test should call the path all the way to trigger_callback() and fail the Chord, otherwise a Chord can never fail.
It suprises me that this is not the case with your proposed changes, since trigger_callback should be True, deps.ready() should be True so both trigger_callback() and chord_counter.delete() should have been called.

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@AllexVeldman AllexVeldman Feb 28, 2025 •
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OK, it took some time but I figured out why this change makes the test pass (which is still not correct).

It's because the MagicMock used for the request parameter to mark_as_done() and mark_as_failure() does not have ignore_result = False set. This in turn would make request.ignore_result evaluate to True, skipping saving the result, which is needed to have deps.ready() work properly. Since we did not rely on deps.ready() in the previous state this never surfaced as an issue.

Add ignore_result = False to the MagicMock and reverting the test changes will fix the test.


request.chord.delay.assert_not_called()

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