The script is based on community work from:
https://forum.netgate.com/topic/151351/email-notification-openvpn-client-connect-common-name/78
Pfsense
Telegraf package
Open VPN
In your Open VPN server custom options, you will need to add the following line:
client-disconnect /root/disconnect.sh
Place the disconnect.sh script to /root.
Make the script executable (chmod 555 disconnect.sh).
Copy the contents of disconnect.sh in this repository to your new file.
In the Telegraf Additional Configuration box, add the contents of telegraf.conf.
Data should now be present to pull from InfluxDB.