This enables the standard `/metrics` endpoint. A scrape will trigger the
collection of IPMI metrics from the local machine (that the exporter is
running on).
Instead of failing hard and not returning any metrics at all if just one
(or two) of the three calls to IPMI tools fail, return whatever data was
properly received and add a `collector` label to the `ipmi_up` metric
indicating which tools failed.
This is only a small step towards the concept of "collectors" like they
exist e.g. in the node exporter, but it should help solve #1. Additional
functionality, like disabling certain collectors, can be built on top of
this.
Currently, an error in the `ipmi` collector is always logged as an error,
In the `dcmi` and `bmc` collectors, an error retrieving the data is only
logged as debug output, but an error processing retrieved data is logged
as an error. This should cover most use cases and will be improved upon
once more work is done to make the collectors selectable per scrape.
Conrad Hoffmann