Expose, or allow inserting, the http.Client used by the api.Client #932
Description
When querying Prometheus behind a proxy or authentication layer, certain extra authentication information may be necessary. Normally, this could be handled by giving a custom http.Client, however, the api.Client implementation httpClient wraps the http.Client and only exposes the address and http.RoundTripper to the user.
As per the go docs, the http.RoundTripper is explicitly not handling things like redirects, authentication or cookies and cannot be used to this end.
In my own project, I could work around it by creating my own implementation of the api.Client interface, essentially duplicating the existing code. But I think it would be beneficial to expose the internal http.Client in some way.
Potentially:
type Config struct {
// The address of the Prometheus to connect to.
Address string
// Client is used by the Client to drive HTTP requests. If not provided,
// a new one is allocated
Client *http.Client
// RoundTripper is used by the Client to drive HTTP requests, if no
// client has been passed in as well. If not
// provided, DefaultRoundTripper will be used.
// Deprecated: set it directly on the Client instead
RoundTripper http.RoundTripper
}
// ...
func (cfg *Config) client() *http.Client {
if cfg.Client == nil {
// Set the roundtripper for old code
return &http.Client{
Transport: cfg.roundTripper()
}
}
return cfg.Client
}
// ...
// NewClient returns a new Client.
//
// It is safe to use the returned Client from multiple goroutines.
func NewClient(cfg Config) (Client, error) {
u, err := url.Parse(cfg.Address)
if err != nil {
return nil, err
}
u.Path = strings.TrimRight(u.Path, "/")
return &httpClient{
endpoint: u,
client: *cfg.client(),
}, nil
}