> Good hint. However, I'm moving the join out of the provider (the full path to puppetdb conf file will be passed as you suggest later).

No, I was suggesting that it need not be passed at all by default.

> Is there a preferred way how to join paths in the puppet language (other than "${path}/file.ext")?

Not that I'm aware of. join in stdlib sort of of does it, but its not a path join in that sense.