[GuyPostington]

Ways to monitor for cert expiry in no particular order:

1) Prometheus + blackbox_exporter https://www.robustperception.io/get-alerted-before-your-ssl-...

2) Sensu/Nagios https://github.com/sensu-plugins/sensu-plugins-http/blob/mas...

3) Openssl in a crontab:

    echo | openssl s_client -connect ${DOMAIN}:443 -servername ${DOMAIN} -verify_hostname ${DOMAIN} 2>/dev/null | openssl x590 -noout -startdate -enddate