Expose Host property in HTTPClientConfig

Author: jkroepke

config/http_config.go

@@ -319,6 +319,9 @@ type HTTPClientConfig struct {
 	// The omitempty flag is not set, because it would be hidden from the
 	// marshalled configuration when set to false.
 	EnableHTTP2 bool `yaml:"enable_http2" json:"enable_http2"`
+	// HTTPHost optionally overrides the Host header to send.
+	// If empty, the host from the URL is used.
+	HTTPHost string `yaml:"http_host,omitempty" json:"host,omitempty"`
 	// Proxy configuration.
 	ProxyConfig `yaml:",inline"`
 	// HTTPHeaders specify headers to inject in the requests. Those headers
@@ -664,6 +667,8 @@ func NewRoundTripperFromConfigWithContext(ctx context.Context, cfg HTTPClientCon
 
 		if opts.host != "" {
 			rt = NewHostRoundTripper(opts.host, rt)
+		} else if cfg.HTTPHost != "" {
+			rt = NewHostRoundTripper(cfg.HTTPHost, rt)
 		}
 
 		// Return a new configured RoundTripper.

config/http_config_test.go

@@ -1745,6 +1745,33 @@ func TestHost(t *testing.T) {
 	}))
 	defer ts.Close()
 
+	config := DefaultHTTPClientConfig
+	config.HTTPHost = "localhost.localdomain"
+
+	rt, err := NewRoundTripperFromConfig(config, "test_host")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	client := http.Client{
+		Transport: rt,
+	}
+	_, err = client.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestHostWithNewRoundTripperFromConfig(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Host != "localhost.localdomain" {
+			t.Fatalf("Expected Host header in request to be 'localhost.localdomain', got '%s'", r.Host)
+		}
+
+		w.Header().Add("Content-Type", "application/json")
+	}))
+	defer ts.Close()
+
 	config := DefaultHTTPClientConfig
 
 	rt, err := NewRoundTripperFromConfig(config, "test_host", WithHost("localhost.localdomain"))