The existing implementation consists of a collector that exports
information from a tls.ConnectionState returned by the prober function.
This won't necessarily integrate well with additional probers that
retrieve certs from sources other than a tls handshake (from file, for
instance).
I've made the probing more generically expandable by removing the
collector and instead registering and collecting metrics inside the
prober. This makes it possible to collect the same metrics in a
different way, or collect different metrics depending on the prober.
There are a number of reasons for this change:
- Modules allow a single instance of the exporter to be configured with numerous
different tls configs. Previously you had to run a different exporter for each
combination.
- Adding new and more complicated options to the exporter should be easier with
modules than if I was to go down the route of accepting configuration directly through url params
- I prefer defining a specific prober (https,tcp) over using the URL to guess
what the user wants
