RabbitMQ Consume Messages in Batches and Ack them all at once

Question

I have a RabbitMQ queue in which I post thousands of messages. I need a background Service that will:

• Retrieve the messages in batches of 100 messages
• Store those 100 messages in a Database
• Ack all 100 messages at once
• Proceed with the next batch of 100 messages

I'm using the RabbitMQ Client to listen for messages, but I don't know how to "batch" them.

Does anyone has a working example on how to get my messagess 100-100 at a time and ACK them all at once after they have been saved in a DB?

Thanx a lot in advance

Answer 1

You want to use the "prefetch" and "multi ack" features -

• Prefetch - https://www.rabbitmq.com/consumer-prefetch.html
• Multi-ack - https://www.rabbitmq.com/confirms.html#consumer-acks-multiple-parameter

This is what you'll do in your code:

• Open a connection and channel
• Set the channel prefetch to 100
• Start a consumer. The callback you register for your consumer will start being called with messages. You will have to save these messages in a list or other data structure
• Once you have received 100 messages, save the delivery tag of the 100th message and do your database work.
• Ack the 100 messages by setting "multi ack" to true and use the delivery tag of the 100th message.
• RabbitMQ will send the next 100 messages in the same manner

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