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

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)



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".



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

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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