Transactions and delivery guarantees

NuGet Package: NServiceBus.RabbitMQ (6.x)
Target Version: NServiceBus 7.x

The RabbitMQ transport supports the following transport transaction modes:

  • Transport transaction - receive only
  • Unreliable (transactions disabled)

Transport transaction - receive only

When running in ReceiveOnly mode, messages are consumed in manual acknowledgment mode. Successfully processed messages are acknowledged via the AMQP basic.ack method, at which point the broker will remove them from the queue. Failed messages that need to be retried are re-queued via the AMQP basic.reject method.

If the connection to the broker is lost for any reason before a message can be acknowledged, even if the message was successfully processed, the message will automatically be re-queued by the broker. This will result in the endpoint processing the same message multiple times.

Unreliable (transactions disabled)

Similar to ReceiveOnly mode, messages are consumed in manual acknowledgment mode, but regardless of whether a message is successfully processed or not, it is acknowledged via the AMQP basic.ack method after the processing attempt. This means that a message will be attempted once, and moved to the error queue if it fails.

Since manual acknowledgment mode is being used, if the connection to the broker is lost for any reason before a message can be acknowledged, the message will automatically be re-queued by the broker. If this occurs, the message will be retried by the endpoint, despite the transaction mode setting.

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