Pamod In QOS2 there is no actual notification of delivery to the subscribers. There is a "two-phase commit" approach to sending the message: first the message is stored and there is a PUBREC message to say that its stored, and then there is a PUBREL message from the client saying it can be delivered. At this point the broker *starts* the delivery process, and sends back a PUBCOMP to the sender.
I'm not sure how this plays into the architecture, but the client never finds out that the message *has* been delivered to all subscribers. At least this is my reading of the spec. Paul On 23 October 2014 11:17, Pamod Sylvester <[email protected]> wrote: > Hi All, > > The current MB kernal architecture, complies to a model which takes each > of the messages published through the store before delivering to the > subscribers. Comparing against AMQP, MQTT QOS 2 is dependent on publisher > side acknowledgments, where the publisher should be notified at a time > where the message was delivered to its subscriber/s. > > To address the use cases (QOS 0,2) we need to have a design which will > allow broker to broker communication in a relational manner between the > nodes for the following reasons, > > a) QOS 0 - This level of QOS should be a performance oriented level, > taking it through the store will by default make the level QOS 1 and also > will break the intention of using the level 0. > b) QOS 2 - for publisher to be notified upon the delivery of the message > to its subscribers we need to communicate among the brokers. We could use > Hazelcast alternatively but IMO it could slow things down so better stick > with a proper communication model. > > Based on the above facts we need to include a mechanism to allow broker to > broker communication that would comply with both AMQP and MQTT. Should we > consider introducing this mechanism for the forthcoming MB 3.0.0 release or > should we stick with shipping MQTT having only QOS 1 and support levels 0,2 > for the next release. > > WDYT ? > > Thanks, > Pamod > > -- > *Pamod Sylvester * > *Senior Software Engineer * > Integration Technologies Team, WSO2 Inc.; http://wso2.com > email: [email protected] cell: +94 77 7779495 > -- Paul Fremantle CTO and Co-Founder, WSO2 OASIS WS-RX TC Co-chair, Apache Member UK: +44 207 096 0336 blog: http://pzf.fremantle.org twitter.com/pzfreo [email protected] wso2.com Lean Enterprise Middleware Disclaimer: This communication may contain privileged or other confidential information and is intended exclusively for the addressee/s. If you are not the intended recipient/s, or believe that you may have received this communication in error, please reply to the sender indicating that fact and delete the copy you received and in addition, you should not print, copy, retransmit, disseminate, or otherwise use the information contained in this communication. Internet communications cannot be guaranteed to be timely, secure, error or virus-free. The sender does not accept liability for any errors or omissions.
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