A collection of proxy backends for the Grafana JSON API plugin. See:
These plugins are very simple. They convert from a non-supported format, where no community plugin exists, to an API compatible with the JSON API plugin.
If you're exposing metrics and are using Prometheus, you should definitely consider a Prometheus exporter over a proxy backend like the ones found here. This style of backend is useful for things that wouldn't fit well in a Prometheus (or other) TSDB.
All of these plugins implement some very simple TTL caching to reduce load on the backend. The default cache TTL is 1800 seconds (30 minutes) and is configurable.
This proxy returns an iCal feed as annotations. I wanted to have events from a shared maintenance calendar available on a status page in Grafana. There is a Google Calendar datasource backend plugin, but I wanted something less tied in. iCal is pretty much the defacto calendar sharing standard format.