Chord awaited even if not explicitly requested

[emmepra]

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Related Issues and Possible Duplicates

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Behavior

My goal is to launch a chord from a FastAPI call, which creates N different Tasks to be executed, then not waiting for it to complete, just returning Response 200. To do so I first used the following notation:

header = [exec_calc.s(x) for x in args]
callback = do_checks.si() # no need for header results as argument here
chord(header)(callback)

Unfortunately it resulted in exploding FastAPI process and no return since chord completion, not desired. So I used this other notation hoping for a different ending:

header = [exec_calc.s(x) for x in args]
callback = do_checks.si() # no need for header results as argument here
chord(header, callback).async()

But still, same behavior happening: FastAPI process exploding and nothing returned.

It's not very clear to me how chord should be used and if they can actually be used asynchronously or not. Maybe there's some specific behavior not properly described in their documentation.

[AlexPetul]

This line chord(header, callback).async() is almost correct, however, chord does not define such method as async(). Use delay() or apply_async() instead. For example, that's how i used chord in combination with chain:

chord(
    run_vm_playbooks,  # Will run in parallel
    chain(
        terraform.refresh.si(),
        start_cloned_sandbox.si(),
    ),
).delay()

If you call chord object chord(...)(), you program will wait until it finishes the execution. Use one of those methods, mentioned earlier, depending on your requirements.

[emmepra]

Thanks for the prompt feedback!
However .async() was actually a typo, I used .apply_async() in the second case but still it wasn't working as expected.
In particular header is a very big list (len(args) > 1.000.000) of exec_calc() tasks which should be run asynchronously then called back by callback.

I was expecting the group part of it running asynchronously as if been called by group(..).apply_async(), but it seems like it got stuck for some reason. Am I missing something?