paho mqtt qos

retryInterval is a hold over from MQTT 3.1, when it was recommended that MQTT publish requests where QoS >1 that were not responded to were retried after some interval. The requirement to do this was removed in MQTT 3.1.1. From my experience, retries usually only made bad situations worse by increasing the load on already overloaded systems.

minRetryInterval and maxRetryInterval apply to automatic reconnect and are the lower and upper limits of the that reconnect interval, doubling on each failed attempt. I see that the documentation is lacking in this regard, I will update it.

ref:

Paho MQTT C Client Library: MQTTClient_connectOptions Struct Reference

paho mqtt c 源码分析-5 (Qos） - 简书

https://github.com/eclipse/paho.mqtt.c/issues/297

What is MQTT Quality of Service (QoS) 0,1, & 2? – MQTT Essentials: Part 6