(406, 'PRECONDITION_FAILED - unknown delivery tag 2') error

[Akshaya]

Hi,

I am running the rabbitMQ message parsing as a python service. It is frequently failing with below error. Have not set no_ack=True anywhere.

How to fix this?

pika.exceptions.ChannelClosed: (406, 'PRECONDITION_FAILED - unknown delivery tag 2')

-Akshaya

[Michael Klishin]

The doc guide that you are looking for is [1]. Please read the entire

part about consumer acknowledgements but specifically [2].

1. http://www.rabbitmq.com/confirms.html

2. http://www.rabbitmq.com/confirms.html#consumer-acks-double-acking

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[Akshaya]

Thank you for the reply. Have read the documents. Shall analyze further about this.

Have also used to reschedule the unacknowledged messages.

ch.basic_recover(requeue=True)

This may be a reason for this?

-Akshaya

On Tuesday, July 24, 2018 at 3:55:11 AM UTC+5:30, Michael Klishin wrote:

The doc guide that you are looking for is [1]. Please read the entire

part about consumer acknowledgements but specifically [2].

1. http://www.rabbitmq.com/confirms.html

2. http://www.rabbitmq.com/confirms.html#consumer-acks-double-acking

On Mon, Jul 23, 2018 at 2:44 PM, Akshaya <nach...@gmail.com> wrote:

Hi,

I am running the rabbitMQ message parsing as a python service. It is frequently failing with below error. Have not set no_ack=True anywhere.

How to fix this?

pika.exceptions.ChannelClosed: (406, 'PRECONDITION_FAILED - unknown delivery tag 2')

-Akshaya

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[Michael Klishin]

It could be. Explicit recovery of consumers has been a deprecated feature for years

(note how our docs never mention it except for the protocol document).

It would be easier for you (and members of this list alike) to reason about what's going on

from a traffic capture [1].

1. http://www.rabbitmq.com/amqp-wireshark.html

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[Akshaya]

Thank you. Shall try to implement wireshark.

BTW, what is the alternate way to recover the unacknowledged messages?

The below is my actual requirement related to unack messages:

- Akshaya

[Akshaya]

Thank you. Shall try to implement wireshark.

BTW, what is the alternate way to recover the unacknowledged messages?

The below is my actual requirement related to unack messages:

        1. consume the messages in parallel from a queue.

        2. If the particular path in the message is already in use, then wait for sometime

        3. This waiting messages will be in unacknowledged state. So requeue it again and consume the same after some time.

This can be achieved by any other way?

[Michael Klishin]

I don't understand the 3rd item, sorry.

[1] should cover everything you need to know. You can explicitly requeue N messages with the basic.nack method (a protocl

extension) or close and open a new channel (this is too extreme for most cases). basic.recover is not necessary to requeue

per se (it was introduced many years ago to let consumers indicate that they are no longer overloaded and the broker can continue

delivering messages, optionally with requeueing the currently unacknowledged ones).

1. http://www.rabbitmq.com/confirms.html

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[Akshaya]

Thanks a lot. One final query.

I could not find the proper example anywhere for the basic nack using python.

Any boolean value needed in ch.basic_nack() or just this would be enough to requeue the message?

-Akshaya

[Michael Klishin]

See Pika documentation for that function. There are two boolean parameters it accepts.

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