I am using Vernemq MQTT broker with node-red both running in Docker in a Traefik Stack (though I don't expect that is the problem). I am seeing a strange symptom with repeated messages when subscribing to a topic. If I have a simple flow as in the one below with an inject node publishing a topic v…

I have seen this long ago when i was new to node-red (so didnt report it - thought it was my fault); In the end I put an RBE after the subscribe node. This nipped it in the bud but it was not the real solution. Since then I have began to think somehow there are 2 event handlers linked up to the su…

I have tried restarting node-red and Vernemq. There was a bug a year ago that caused similar issues, but it was not broker dependent I don't think. It was fixed in 0.20.4 apparently. I can't use an RBE as a workaround as I want to receive all the messages even if they are the same, but I am worki…

So is this persistent with vernemq? e.g. if you change to a local or other remote broker, does the issue go away?

[image] Steve-Mcl: if you change to a local or other remote broker, does the issue go away? Yes, I think I mentioned that if I switch to a mosquitto broker that there is no problem. It returns if I go back to Vernemq.

Any thoughts on this @dceejay , @knolleary ?

... err maybe don't use Vernemq ?

You are hitting an "interesting" edge case in the MQTT spec. I say "interesting" because I spent hours upon hours discussing it as part of the MQTT standards group. It all comes down to how a broker handles overlapping subscriptions. In your scenario, you have a subscription to tydwr/testit/xxx an…

[image] knolleary: avoid overlapping subscriptions. In fact it also seems to happen if you have two nodes both subscribing to the same topic (so again they are overlapping). For example two nodes subscribing to tydwr/testit/xxx. That is something that I do a lot in order to keep separation …

I can't use an RBE node as I do need a message to come through every time, even if it is the same value as the previous one. Two reasons, firstly it goes into a node-red-contrib-pid which expects regular process values even if there is no change, and secondly it is going to an influx database and I…

Repeated messages with Vernemq mqtt broker

General

Colin 18 May 2020 07:42 13

Sorry, I don't see how that distinguishes between two messages that happen to have the same values and a repeated message?

I have a workaround that functions perfectly. Since I know that good messages for each topic are never going to be closer together than at least a few seconds then a Delay node configured like this does it.

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Repeated messages with Vernemq mqtt broker

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