Reliable Messaging with RabbitMQ: Acknowledgments, Durability, and Persistence

One of the main reasons people use RabbitMQ is reliability. In many systems, losing a message is not acceptable. Imagine if an order is placed in an e-commerce system but disappears before the payment service sees it, that would be a big problem.

RabbitMQ offers three important features to ensure reliable messaging: Acknowledgments, Durability, and Persistence. Let’s understand each of them.

1. Acknowledgments (ACKs)

What it is

Acknowledgment means the consumer tells RabbitMQ that it has received and processed a message successfully.

• If the consumer sends back an ACK → RabbitMQ can safely delete the message from the queue.
• If the consumer does not send ACK (because it crashed or disconnected) → RabbitMQ will re-send the message to another consumer.

Example

Goal: Consumer uses manual ACK. On success → Ack; on failure → Nack(requeue=true) so the message is re-delivered.

Consumer:

// ACK EXAMPLE: manual ack + retry on error
conn := mustConn(); defer conn.Close()
ch, err := conn.Channel()
if err != nil { log.Fatal(err) }
defer ch.Close()

// declare a queue (durability optional here; focus: ACK)
_, err = ch.QueueDeclare("orders_queue_ack", true, false, false, false, nil)
if err != nil { log.Fatal(err) }

// fair dispatch: 1 message at a time
if err := ch.Qos(1, 0, false); err != nil { log.Fatal(err) }

msgs, err := ch.Consume("orders_queue_ack", "", false, false, false, false, nil)
if err != nil { log.Fatal(err) }

for d := range msgs {
	log.Printf("process: %s", d.Body)
	// simulate work
	if string(d.Body) == "fail" {
		// negative ack -> requeue for retry
		_ = d.Nack(false, true) // multiple=false, requeue=true
		continue
	}
	time.Sleep(500 * time.Millisecond)
	_ = d.Ack(false) // confirm processed
}

Options

• Auto ACK: RabbitMQ deletes the message immediately after delivery (less safe).
• Manual ACK: The consumer decides when to send ACK (recommended for reliability).