Bandwidth tracking and reporting

[ryangriggs]

Is your feature request related to a problem? Please describe.
No. My feature request is related to monitoring statistics of the MQTT connection.

Describe the solution you'd like
It would be nice to have some telemetry properties available in the MQTT class, that provide tracking of the following connection statistics:

• Bandwidth usage (upload and download as separate properties)

• Number of reconnections

• Also expose functions or setters to reset the counters as needed. (Don't reset between connections)

Example usage:

// Create a mqtt object and connect to the server:
const mqtt = require('mqtt');
mqtt.connectAsync(uri, { ...props })
.then((conn) => {
   // On successful connection, set up a repeating task to log bandwidth usage
   setInterval( ()=> { bandwidthReport(conn); }, 60000 );
});

function bandwidthReport(connection)
{
    console.log(`MQTT Bandwidth Usage:  Download: ${connection.bandwidthDownload} bytes, Upload: ${connection.bandwithUpload} bytes, Reconnections: ${connection.reconnectionCount}`);
}

These parameters should already be available from the underlying socket object, or could easily be counted within the methods which transmit data over the wire (i.e. before calling socket.write() and within the data event handler).

Describe alternatives you've considered
N/A

Additional context

[robertsLando]

Would you like to submit a PR? I would enable statistics tracking behind an option BTW

[ryangriggs]

Would you like to submit a PR? I would enable statistics tracking behind an option BTW

Can you explain what you mean "behind an option"? Do you mean that they can be enabled/disabled by setting a flag (i.e. give the user an option to enable them) or do you mean behind an optional plugin of some sort? Sorry for the confusion.

[robertsLando]

Behind a client option because this comes with a little overhead that some users may want to avoid if not needed :)

[ryangriggs]

So, something like a client.statisticsEnabled boolean on the client instance (disabled by default), which would enable stats tracking if set to true?

[robertsLando]

yeah