How to use prometheus_client describe method?

[Elliott Balsley]

I'm working on a custom exporter, using the prometheus_client python library.  I've read the documentation about auto_describe but it's not clear.

With auto_describe=True, the collect() method runs twice on each scrape.  This is bad because it puts extra load on the target device.

I can fix this by adding a describe() method that returns an empty list.  That's easy, but I want to follow best practices.  Is there any reason I should return a proper list of metrics instead?

If I did want to implement a proper describe method, would it need to return a list of GaugeMetricFamily objects with name, help text, and labels?  It seems like a lot of duplicated code with the collect() method...  Are there any good example exporters to look at?

My code is here: https://gist.github.com/llamafilm/0c2ce612273db11ad9d8edcd0643ab44

I'd be happy to hear any other feedback too since this is my first exporter.

Thanks!