Connection is reset when receiving a payload that exceeds the max-packet-size limit?

[tsauerwein]

Hi! We noticed that if a payload is received that exceeds the configured "max-packet-size", the whole connection is reset.

Maybe it's due to our particular use-case, but with this behaviour our application would end up in a "re-connection loop" as long as the big payload is on the MQTT bus. Basically the steps would be:

1. MQTT connection is established
2. Subscribing to topics
3. Big payload is received -> disconnect
4. Go to 1

Did we understand the behaviour correctly? Is there an option not to disconnect in case of a PayloadSizeLimitExceeded error?

Thanks!

[swanandx]

Hey,
whether it tries to reconnect or not depend on how you are using rumqttc. Basically if you call poll it tries to connect.

Is there an option not to disconnect in case of a PayloadSizeLimitExceeded error?

as per protocol, it should disconnect! but if you don't want to disconnect, maybe just not configuring max-packet-size would solve your issue?

[tsauerwein]

Thanks for your reply!

but if you don't want to disconnect, maybe just not configuring max-packet-size would solve your issue?

Is that possible? It seems there is a default of 10 * 1024 bytes.

[swanandx]

you can update the value using set_max_packet_size, but it looks like we will just use the default value you mentioned!

Maybe we should let users specify None? for now, you can try to set it to some value large enough so your application won't crash?

thanks!

[tsauerwein]

Yes, that's what we are doing for now. Thanks for your feedback!