Re: [paho-dev] [ EXTERNAL ] Re: End-to-end response

[Andy Stanford-Clark <ANDYSC@xxxxxxxxxx>]

MQTT QoS works "hop
by hop", so a QoS 2 message will travel at QoS 2 from publisher to
broker 1, and then from broker 1 to broker 2, and then from bnroker 2 to
the subscriber. There is no way for the publisher to know, at the protocol
level, whether it has successfully moved beyond the broker to which it
is connected (broker 1).

The only way to
do this is at the application level...
 
The receiving
application would publish an acknowledgement back on a topic on which the
original sender is listening.

If you need to
know that it's got to the last *broker* but not necessarily received by
the final subscriber, you could perhaps run a little application on the
broker machine which subscribes to and acknowledges all messages (at the
application level), which would confirm it had got to the broker box, but
not yet necessarily delivered to the final destination subscriber.

Andy

Andy Stanford-Clark
IBM CTO - UK and Ireland

Distinguished Engineer, Master Inventor, IBM Quantum Ambassador, 
Member IBM Academy of Technology, Fellow BCS
Visiting Professor at Newcastle, Southampton and UEA.

Tel: +44 (0)7801 787096 [internal: 37 277624]   twitter: @andysc




From:
       "Kumar,
Pankaj" <pankaj_kumar2@xxxxxxxxxx>
To:
       General
development discussions for paho project <paho-dev@xxxxxxxxxxx>,
"Paul, Base V" <base_paul@xxxxxxxxxx>
Date:
       15/10/2020
08:21
Subject:
       [EXTERNAL]
Re: [paho-dev] [ EXTERNAL ] Re:  End-to-end response
Sent
by:        paho-dev-bounces@xxxxxxxxxxx

---

+ Base Paul. From: Kumar,
Pankaj Sent: Thursday, October 15, 2020 12:48 PM To:...

This Message Is From an External Sender

This message came from outside your organization.

+ Base Paul.

 

From: Kumar, Pankaj
Sent: Thursday, October 15, 2020 12:48 PM
To: General development discussions for paho project <paho-dev@xxxxxxxxxxx>
Subject: RE: [ EXTERNAL ] Re: [paho-dev] End-to-end response

 

Thanks for the quick response.

 

Let me add some more detail here.

 

Our ultimate aim is to track the delivery of messages to right most Broker in a reliable way.

 

My current setup is as following. (No issues here)

 

Client ---------- Broker ----------- Server

• Client sends QOS2 message to Broker.
• Broker sends response(PUBCOMP) back to Client
• Transaction completes

Note:
We don’t care how Broker forwards that message further to Server

 

Now, we have added another Broker in between as following.

 

Client ------------ Intermediate Broker ------------ Broker ---------- Server

• Client sends QOS2 message to Intermediate Broker
• Intermediate Broker sends response (PUBCOM) back to Client
• Client can’t mark transaction complete as there is no reliable way to know when message is delivered to right most Broker.

Looking for a solution to help Client track the response from final broker. Again we don’t care how final/right-most broker further forwards that message to Server.

 

Regards

Pankaj

 

From: paho-dev-bounces@xxxxxxxxxxx <paho-dev-bounces@xxxxxxxxxxx> On Behalf Of Dominik Obermaier
Sent: Thursday, October 15, 2020 12:20 PM
To: General development discussions for paho project <paho-dev@xxxxxxxxxxx>
Subject: [ EXTERNAL ] Re: [paho-dev] End-to-end response

 

[ EXTERNAL ]

Hi Pankaj,
MQTT 5 has a concept
called "Request
/ Response Pattern"
that will do exactly what you want.
However, it seems you
are bridging MQTT brokers. Depending on the broker you're using this might
not work as not all brokers support MQTT 5 for bridging. Last time I checked
mosquitto for example did not yet have MQTT 5 support for bridges.
Best,
Dominik
On 15 Oct 2020, at
7:59, Kumar, Pankaj wrote:

Hello Dev,

 

Is there a way to get end-to-end response from a server which is two brokers away from client ?

 

Client ----------- Broker-1 ----------------Broker-2--------------Server

 

Looking for MQTT level solution without application level topic/messaging. I am using MQTT-5.

 

Regards

Pankaj

 

 

 

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