How do you reject work with the GRPC ext client?

In the dapr-ext-grpc documentation page, we see the following example for subscribing to TOPIC_A on the pubsub publish subscribe component.

@app.subscribe(pubsub_name='pubsub', topic='TOPIC_A')
def mytopic(event: v1.Event) -> None:
    print(event.Data(),flush=True)

The document doesn’t say how one ACKs a message. Are messages ACKed when the decorated function (mytopic, in the example above) is called, or when it returns?

If a message is only ACKed when the decorated function returns, how do I prevent redelivery when the decorated function needs to do a long-running operation? Or how do I reject work until a long-running operation completes?

What happens if an exception is raised from the decorated function? Will dapr try to redeliver the message?

Thanks!

[wcs1only]

One approach would be to allow the callback function to return a TopicEventResponse object.

[renatolfc]

#336 is my attempt at solving this issue following @wcs1only’s suggestion.

Please let me know if it needs improvements, as it’d be super nice for me to be able to intruct dapr to retry/reject messages when using the grpc client.