How to receive messages by parts?

[ZedZipDev]

How to receive messages from queue by parts?
For example, I have a Queue (N messages) and clients need to receive by n<N messages from the queue but do not receive messages twice. How to implement this approach? I.e. every client reads like window by n msgs, then next n msgs and so on.

[lukebakken]

https://www.rabbitmq.com/consumer-prefetch.html

An application could receive a message twice if something happens during the processing of a message. For instance, if you have only one consumer with a prefetch of 10, and while processing those 10 messages your application crashes before acknowledging the messages, they will be re-delivered when the application starts again.

If you will be processing messages in batches you should also look at the multiple field for acks - https://www.rabbitmq.com/confirms.html#consumer-acks-multiple-parameter

[ZedZipDev]

Yes, excluding some crashes etc.

I have n consumer applications which read the same queue (now it is one queue). That is my question:
each of n clients should receive messages only once from the queue.