Intermediate Cyclic Broker Publish delays

Mosquitto MQTT Broker
1

I have one topic “DCNET/DT/” that is a JSON string of Tag : value pairs
{“Year”:“2022, “Month”:“2”, “Day”:5, “Hour”:12” ,“Minute”:“32”, “Second”:“47”}.

A CMT-SVR102 publishes this topic once per second as the system clock ticks. The CMT also Subscribes to this topic and displays on the virtual HMI screen(CMT Viewer). MQTT Explorer also subscribes to the “DCNET/DT/” topic. Both CMT Viewer and MQTT Explorer display the same value being published by Mosquitto. Wireshark captures one individual broker publish per second for 30 seconds. Zero Broker publish for 21.8 seconds, 21 publishes in 1.2 seconds then returns to 1 publish per second. This cycle continues to repeat. Is there a configuration setting that can cause this issue. Seems to confirm the bottle neck is at the broker just don’t understand why.

2

The only thing I can think of that could cause this in the configuration settings would be if you had persistence configured to save to disk every 30 seconds and the amount of data being saved / the speed of the disk was causing a 21.8 second delay. That seems pretty unlikely to me, but it’s worth a try. The simple change would be moving to persistence false in the config if it is enabled.

Regards,

Roger