how to filter duplicate message for consumed thing binding MQTT with Qos1

[yidingdian]

consumed thing binding mqtt recieved duplicate message , I want to filter the message before it arrived at node-wot, but I could not get the message. Is there any way to filter out these duplicate messages in the node-wot or filter them out before the messages reach the component ?

[relu91]

Hi! Thank you for using node-wot. Filter MQTT is heavily application dependent, and therefore, node-wot does not really support a way to filter them before passing them over to the CosumedThing object. You could, in theory, rewrite the whole MQTT client implementation and filter messages there, but it is quite an overhead. Why can't you filter them out in the application event handler? Another option is to increase QoS to 2.

[yidingdian]

Thanks @relu91 for a very detail explanation. The information used to filter duplicate messages , such as id and timestamp is placed in the properties of mqtt v5, application could not get the informations with binding-mqtt, then unable to filter the messages. It seems that the simple method is to incease Qos to 2.
Thank you again.

[egekorkan]

@yidingdian thanks for letting us know. I don't foresee how we can do that without QoS2 as nothing in the payload says that they are duplicate. MQTT5 is an ongoing discussion but that can be indeed a solution.