Some scripts to monitor the Domoticz process:

#!/bin/sh
# Get Domoticz Process CPU
ps -C domoticz -o %cpu | tail -n +2

#!/bin/sh
# Get Domoticz Process Memory
ps -C domoticz -o %mem | tail -n +2

#!/bin/sh
# Get Domoticz Folder Size
du -shb /home/pi/camillo/domoticz-code | awk -F " " {'print $1'}

Hi, nice work on MQTT, however, to understand better what You are doing and maybe help You with some testing or developing, can You draw a picture of how this MQTT works in the Domoticz environment and how is the hardware/software architecture?

How the remote Arduinos talk with the MEGA? Via ...

Yes!! I did a couple of simple sh scripts for generic Linux I can publish as well