Add probe_ssl_last_chain_creation_timestamp_seconds

[f-booh]

Hi

We would like to have the metric probe_ssl_last_chain_creation_timestamp_seconds which shows when a certificate was created.

Usually:

• Manual certificates are created for a year, and we need to alert early to renew these.
• Automatic renewal typically has a shorter lifetime, we just have to alert shortly before it expires.

Can we have this feature? Does it make sense?

Regards, Frank

[cropalato]

I like the idea. If the certificate is automatically generated using cert-manager, consul-template + Vault, or any other solution, it would be helpful to have an alert for certificates that are older than x% (e.g., 80%).

[electron0zero]

would metrics probe_ssl_earliest_cert_start and probe_ssl_last_chain_start_timestamp_seconds would work, they are being added in https://github.com/prometheus/blackbox_exporter/pull/1382

please chime in that PR and help us better capture this use-case.