What are the reasons why messages in RabbitMQ can go unacked?

Question

Java

Hello. I work from Java with Rabbit using Spring RabbitTemplate. And I can’t figure out exactly when messages can hang in the queue and stay in the unacked state.
I used to think that this could happen due to an unexpected uncaught exception, but according to the application logs, I see that there are no exceptions, and the messages freeze.
Maybe there are other reasons for hanging messages?
PS And if possible, then confirm your words with links to official documentation

Answer 1

If the consumer did not answer ack then it is unacked. This signal must be sent. There are several types out there.