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

["Steve Mullock" <sjmeclipse@xxxxxxxxxx>]

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