Hi Ian,
thank you so much for your advise;
you caught it!! My Mosquitto config is the problem. I have changed the
max_queued_messages option to an unusual very large value and then I've received all the expected messages. No drops. So, I'm almost sure that it is a matter of configuring
max_inflight_messages and
max_queued_messages to fit my specific needs.
Also, I will subscribe to:
$SYS/broker/messages/inflight
$SYS/broker/publish/messages/dropped
to monitor how things evolve.
I need to understand better the effects of tuning these two configuration parameters before being able to have an reasonable configuration but I feel I'm now in the good way. After my latest test (thanks to you) I have found that (it could be of somebody's interest):
- Having a large max_inflight_messages value floods the PAHO subscriber as it is not able to process the receiving message and has to persist message acknowledgements to disk, making the client very slow and the time of service veeeeery large. But, it allow the broker to have a lower max_queued_messages value and use less resources.
- On the contrary, having a low max_inflight_messages value makes possible for the client to process the messages correctly and be more fluent, as it is able to acknowledge messages without need of persist ACKs to disk. But to avoid message drops, it needs that the broker has a greater max_queued_messages value, that implies more resurces comsumption.
So, I need to find a balance of these two parameters.
I really appreciate your help Ian. I was becoming mad.
Kindest regards.
