Supports "Host" custom header for DataSources about grafana-plugin-sdk-go

[marefr]

Having this issue in one datasource you've developed yourself or a community one, if so which one? In general feels like configuring the URL for an HTTP-based datasource populate the host to whatever host is in that URL? Maybe you can provide some additional details why this is important for you and what the specific use case is for modifying the Host header. Thanks

[tan9]

Hi @marefr

In my Kubernetes setup, I'm using Grafana to access multiple Prometheus instances across various Red Hat OCP clusters. Typically, I connect to these Prometheus instances using URLs specific to the targeted OCP clusters. These domains are not registered in DNS, requiring manual configuration of CoreDNS as an equivalent to setting /etc/hosts, since Grafana doesn’t allow configuring the Host header directly.

I noticed Grafana supports custom headers in Prometheus data source configuration. Based on my experience, setting the Host header seemed like a viable solution. However, this didn't work as expected due to the way Go's net/http package uniquely handles the Host header.

There are alternative solutions to this issue, but considering Grafana already has a custom header feature, and the Host header isn't fundamentally different from others, it seems logical to enable its functionality in Grafana. This is regardless of Go's package treating it as a special case.