http_config: Allow customizing TLS config and settings. (#748)

* http_config: Allow customizing TLS config and settings.


Signed-off-by: bwplotka <bwplotka@gmail.com>

* Switched to newTLSConfigFunc

Signed-off-by: bwplotka <bwplotka@gmail.com>

* Addressed comments.

Signed-off-by: bwplotka <bwplotka@gmail.com>

---------

Signed-off-by: bwplotka <bwplotka@gmail.com>

Author: bwplotka

config/http_config.go

@@ -52,7 +52,8 @@ var (
 		http2Enabled:      true,
 		// 5 minutes is typically above the maximum sane scrape interval. So we can
 		// use keepalive for all configurations.
-		idleConnTimeout: 5 * time.Minute,
+		idleConnTimeout:  5 * time.Minute,
+		newTLSConfigFunc: NewTLSConfigWithContext,
 	}
 )
 
@@ -452,8 +453,12 @@ func (a *BasicAuth) UnmarshalYAML(unmarshal func(interface{}) error) error {
 // by net.Dialer.
 type DialContextFunc func(context.Context, string, string) (net.Conn, error)
 
+// NewTLSConfigFunc returns tls.Config.
+type NewTLSConfigFunc func(context.Context, *TLSConfig, ...TLSConfigOption) (*tls.Config, error)
+
 type httpClientOptions struct {
 	dialContextFunc   DialContextFunc
+	newTLSConfigFunc  NewTLSConfigFunc
 	keepAlivesEnabled bool
 	http2Enabled      bool
 	idleConnTimeout   time.Duration
@@ -473,13 +478,23 @@ func (f httpClientOptionFunc) applyToHTTPClientOptions(options *httpClientOption
 	f(options)
 }
 
-// WithDialContextFunc allows you to override func gets used for the actual dialing. The default is `net.Dialer.DialContext`.
+// WithDialContextFunc allows you to override the func gets used for the dialing.
+// The default is `net.Dialer.DialContext`.
 func WithDialContextFunc(fn DialContextFunc) HTTPClientOption {
 	return httpClientOptionFunc(func(opts *httpClientOptions) {
 		opts.dialContextFunc = fn
 	})
 }
 
+// WithNewTLSConfigFunc allows you to override the func that creates the TLS config
+// from the prometheus http config.
+// The default is `NewTLSConfigWithContext`.
+func WithNewTLSConfigFunc(newTLSConfigFunc NewTLSConfigFunc) HTTPClientOption {
+	return httpClientOptionFunc(func(opts *httpClientOptions) {
+		opts.newTLSConfigFunc = newTLSConfigFunc
+	})
+}
+
 // WithKeepAlivesDisabled allows to disable HTTP keepalive.
 func WithKeepAlivesDisabled() HTTPClientOption {
 	return httpClientOptionFunc(func(opts *httpClientOptions) {
@@ -670,7 +685,7 @@ func NewRoundTripperFromConfigWithContext(ctx context.Context, cfg HTTPClientCon
 		return rt, nil
 	}
 
-	tlsConfig, err := NewTLSConfig(&cfg.TLSConfig, WithSecretManager(opts.secretManager))
+	tlsConfig, err := opts.newTLSConfigFunc(ctx, &cfg.TLSConfig, WithSecretManager(opts.secretManager))
 	if err != nil {
 		return nil, err
 	}
@@ -679,6 +694,7 @@ func NewRoundTripperFromConfigWithContext(ctx context.Context, cfg HTTPClientCon
 	if err != nil {
 		return nil, err
 	}
+
 	if tlsSettings.immutable() {
 		// No need for a RoundTripper that reloads the files automatically.
 		return newRT(tlsConfig)