Re: [rabbitmq-users] Using basic.nack with basic.qos

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Michael Klishin

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Feb 28, 2020, 6:58:55 PM2/28/20

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Acks and nacks are identical in RabbitMQ as far as prefetch effects go. My guess is that you are double acking [1] and that closes the channel.

1. https://www.rabbitmq.com/confirms.html#consumer-acks-double-acking

On Wed, Feb 12, 2020 at 10:18 AM Jay <jay...@finn.ai> wrote:

I'm using Pika library in Python.

In my consumer, I set the prefetch count using:

ch.basic_qos(prefetch_count=6)

When I receive 6 messages, I process it and if that fails for whatever reason (DB cursor gets disconnected for example), I want to send a negative ack for multiple messages and requeue those, which I do using:

ch.basic_nack(delivery_tag=method.delivery_tag, multiple=True,requeue=True)

But these messages are still "unacked", and my consumer does not get any more messages.

Going through the docs, I understand that basic_qos allows RabbitMQ to send X number of messages before waiting for an ack, but I assumed a nack would also work and I will continue to receive more messages or even get into a receive/nack loop.
But the consumer just gets stuck after sending the nack.

Am I missing something here? If nack is not supposed to work with prefetch, is there another way to use prefetch and still nack messges?

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