How to ignore old MQTT messages?

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1

Hi there,

I have an automation which is triggered everytime there is a message in a specific MQTT topic:

  trigger:
  - platform: mqtt
    topic: /light/out

The problem is, each time HA restart or automations are reloaded it’s getting triggered even though there is no new message…
I found absolutely no way to get an automation working with only new messages.
The device who is publishing the messages is an ESP8266. The exact C++ line is:

mqttClient.publish(out_topic, String(vout).c_str(), false)

So retain flag is off during publishing.

2

There must still be a retained message there. Use MQTT Explorer to inspect the topic.

Send an empty retained message to that topic, or delete the retained message with MQTT Explorer.

1 Like
3

Thank you so much I deleted everything and now it works flawless :slight_smile: I always thought the retained messages are simply getting overwritten… But they are there practically forever until you delete them manually.

4

They are only overwritten by other retained messages.

They can be deleted by sending a retained empty message.