[rabbitmq-discuss] MQTT plugin message delivery mode

Simon MacMullen simon at rabbitmq.com
Wed Jan 29 13:13:48 GMT 2014

Please keep rabbitmq-discuss on CC.

On 29/01/14 13:09, Jon Vollmer wrote:
> Thanks for the info Simon.  I think that is an area where documentation
> could be improved because the QoS concept really is different from the
> concept of message persistence, it really only deals with message
> delivery in the MQTT spec.

QoS *does* deal with persistence.

 From section 3.3 PUBLISH:
> PUBLISH messages can be sent either from a publisher to the server,
> or from the server to a subscriber. The action of the recipient when
> it receives a message depends on the QoS level of the message:
> QoS 0
> Make the message available to any interested parties.
> QoS 1
> Log the message to persistent storage, make it available to any
> interested parties, and return a PUBACK message to the sender.

On 29/01/14 13:09, Jon Vollmer wrote:
> It makes sense to combine the concepts though, but I agree that there
> does seem to be a bug.  When publishing a QoS 1 MQTT message I can see
> the "x-mqtt-publish-qos : 1" header but there is no delivery mode header
> and if I stop/start the broker before a consumer grabs the message then
> it will not be there when I restart.

Oh, that's a bug, absolutely.

Cheers, Simon

Simon MacMullen
RabbitMQ, Pivotal

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