A simple prometheus exporter that returns the NotBefore and NotAfter properties of the primary certificate for a list of given domains.

1. Clone repo
2. Build (go build -o exporter main.go)
3. Configure
   • See config-example.json for default values
   • Save changed version as config.json in working directory
4. Run (./exporter)
   • Or ./exporter -config ~/config.json if the config is somewhere else.
5. (Optional) You can use the example-systemd.service file to create the service.
   • Make sure you edit the placeholder values to fit your setup!

• You can view the validity of all your configured domains using a query like:
  • cert_not_after - time()
• To view the soonest expiring certificate (for example to use in a singlestat panel):
  • bottomk(1, sum by (domain) (cert_not_after - time()))

# HELP cert_not_before The primary certificates NotBefore date as unix time'.
# TYPE cert_not_before gauge
cert_not_before{domain="example.com"} 1592149450
# HELP cert_not_after The primary certificates NotAfter date as unix time'.
# TYPE cert_not_after gauge
cert_not_after{domain="example.com"} 1599925450
# HELP cert_fetch_duration Duration of the http call in nanoseconds.
# TYPE cert_fetch_duration gauge
cert_fetch_duration{domain="example.com"} 482473832
# HELP cert_fetch_success Success of the http call as a 0/1 boolean.
# TYPE cert_fetch_success gauge
cert_fetch_success{domain="example.com"} 1