[mosquitto-dev] get the connection events of clients

[Luca Tavanti <luca.tavanti@xxxxxxxxxxxx>]

Dear all,

I'm trying to obtain information about the status of clients as they 
connect and disconnect, in order to track their status. I my deployment 
I have a restricted and known set of clients.
I'm working on the server, so I have full access to the broker.

I would like to build this information automatically, without having the 
client send their status or last will (as I found it is often suggested 
on the web).

It seems to me that one possible way could be to enable 
"connection_messages" in the config and then parse the log.
However, when trying it, I discovered that the line which I'm most 
interested in (which contains the clientID), is not written to the log 
in real time.
For example:
1535990985: New connection from 213.188.207.137 on port 8844.
1535990985: New client connected from 213.188.207.137 as sys-a1b2c3 (c1, 
k60).
1535991025: Client sys-a1b2c3 disconnected.

The second line is generally flushed together with the third (or with 
any successive event that is logged).
It is therefore very difficult to have a complete overview of the status 
of all clients in real time.

Can you suggest me a workaround for this issue?
is there a way to force mosquitto to print the "New client connected 
from 213.188.207.137 as sys-a1b2c3 (c1, k60)" line in real time?

Alternatively, are you aware of a different method to get the real-time 
status of all clients (or the list of currently connected clients)?

Thanks in advance!

Luca