Re: [mosquitto-dev] Bridging and order of (re)sending of messages

[Richard Duivenvoorde <richard@xxxxxxxx>]

Hi Steve,

Thanks for the quick response!

This is actually a good idea (and working, in my my first experiments 
here).
It even looks like the 'retained' value is indeed sent before any 
'queued' messages, so a bonus!
(I'll sent more info about my setup in a reply to Greg)

Regards,

Richard

On 2021-06-21 14:22, Steve Mullock wrote:
> Dear Richard
>
> I am no expert, but could you get the behaviour you want by having the
> local devices publish
> in parallel to a additional topic ".../something/latest" with the
> retained flag set. My
> inderstanding is that only one retained message is kept, so the
> ".../something/latest" topic
> would just have the newwest measurement. Your remote client could then 
> read the
> something/latest before getting other readings from topic 
> ".../something".
>
> regards
>
> Steve
>
>
> Date sent:      	Mon, 21 Jun 2021 13:47:03 +0200
> From:           	Richard Duivenvoorde <richard@xxxxxxxx>
> To:             	mosquitto-dev@xxxxxxxxxxx
> Subject:        	[mosquitto-dev] Bridging and order of (re)sending of 
> messages
> Send reply to:  	General development discussions for the mosquitto 
> project
> 	<mosquitto-dev@xxxxxxxxxxx>
>
> > Hi Devs/All,
> >
> > We have a setup in which a small edge computer with sensor and with
> > limited/bad network connection is set to bridge messages (from local
> > clients) to a central collection point broker.
> >
> > The idea is/was that the broker ON the edge computer will be able to
> > hold the messages and start (re)sending them to the central collector
> > broker when there is a network connection again.
> >
> > This seems to work nicely! But...
> >
> > Question: upon a reconnection, the local broker seems to sent the
> > messages in the order they were received. Plausible in a lot of
> > situations, but in my case we want to have asap the latest known
> > sensor value (and we do not mind receiving older message too off
> > course, but we are mostly interested in the latest). In this case we
> > will at least have the latest values and the computer will not 'waste
> > time/bandwidth' sending the older data (note this is in an emergency
> > response setup, with mobile sensor cars driving in remote areas with
> > bad g4 connections).
> >
> > I could not find a way to configure mosquitto for such an option. Did
> > I miss something or should I create a 'feature request' for it? :-)
> >
> > Would this be of interest for others too, maybe?
> >
> > Thanks for any input, Regards,
> >
> > Richard Duivenvoorde
> > _______________________________________________
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>
> --
> Steve Mullock
>
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