Its very easy to monitor for certificate expiry using the “check_http” script. This is part of the “nagios-plugins” package.

A basic example:

    "checks": {
        "check_cert": {
            "handlers": ["default","email"],
            "command": "/usr/lib/nagios/plugins/check_http -H :::name::: -C 30,7",
            "interval": 1440,
            "subscribers": ["jenkins"]
        }
    }
}

This would check at 24hr intervals. A warning is issued when 30 days remain on the certificate. 7 days remaining will return a critical alert.

Plenty of time to get a replacement organised and installed. 🙂