set user agent on scrape requests to nginx.

client/nginx.go

@@ -12,7 +12,6 @@ import (
 type NginxClient struct {
 	apiEndpoint string
 	httpClient  *http.Client
-	appName	string
 }
 
 // StubStats represents NGINX stub_status metrics.
@@ -32,11 +31,10 @@ type StubConnections struct {
 }
 
 // NewNginxClient creates an NginxClient.
-func NewNginxClient(httpClient *http.Client, apiEndpoint string, appName string) (*NginxClient, error) {
+func NewNginxClient(httpClient *http.Client, apiEndpoint string) (*NginxClient, error) {
 	client := &NginxClient{
 		apiEndpoint: apiEndpoint,
 		httpClient:  httpClient,
-		appName: appName,
 	}
 
 	_, err := client.GetStubStats()
@@ -45,13 +43,7 @@ func NewNginxClient(httpClient *http.Client, apiEndpoint string, appName string)
 
 // GetStubStats fetches the stub_status metrics.
 func (client *NginxClient) GetStubStats() (*StubStats, error) {
-
-	req, err := http.NewRequest("GET", client.apiEndpoint, nil)
-	if err != nil {
-			return nil, fmt.Errorf("failed to create get request %v: %v", client.apiEndpoint, err)
-	}
-	req.Header.Set("User-Agent", client.appName)
-	resp, err := client.httpClient.Do(req)
+	resp, err := client.httpClient.Get(client.apiEndpoint)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get %v: %v", client.apiEndpoint, err)
 	}

exporter.go

@@ -177,11 +177,11 @@ func main() {
 
 	registry.MustRegister(buildInfoMetric)
 
+	userAgent := fmt.Sprintf("NGINX-Prometheus-Exporter/v%v", version)
+	userAgentRT := &userAgentRoundTripper{agent: userAgent, rt: &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: !*sslVerify}}}
 	httpClient := &http.Client{
-		Timeout: timeout.Duration,
-		Transport: &http.Transport{
-			TLSClientConfig: &tls.Config{InsecureSkipVerify: !*sslVerify},
-		},
+		Timeout:   timeout.Duration,
+		Transport: userAgentRT,
 	}
 
 	signalChan := make(chan os.Signal, 1)
@@ -200,9 +200,8 @@ func main() {
 		}
 		registry.MustRegister(collector.NewNginxPlusCollector(plusClient.(*plusclient.NginxClient), "nginxplus"))
 	} else {
-		appName := fmt.Sprintf("NGINX-Prometheus-Exporter/v%v", version)
 		ossClient, err := createClientWithRetries(func() (interface{}, error) {
-			return client.NewNginxClient(httpClient, *scrapeURI, appName)
+			return client.NewNginxClient(httpClient, *scrapeURI)
 		}, *nginxRetries, nginxRetryInterval.Duration)
 		if err != nil {
 			log.Fatalf("Could not create Nginx Client: %v", err)
@@ -225,3 +224,30 @@ func main() {
 	log.Printf("NGINX Prometheus Exporter has successfully started")
 	log.Fatal(http.ListenAndServe(*listenAddr, nil))
 }
+
+type userAgentRoundTripper struct {
+	agent string
+	rt    http.RoundTripper
+}
+
+func (rt *userAgentRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	req = cloneRequest(req)
+	req.Header.Set("User-Agent", rt.agent)
+	return rt.rt.RoundTrip(req)
+}
+func cloneRequest(req *http.Request) *http.Request {
+	r := new(http.Request)
+
+	// shallow clone
+	*r = *req
+
+	// deep copy headers
+	r.Header = make(http.Header, len(req.Header))
+	for key, values := range req.Header {
+		newValues := make([]string, len(values))
+		copy(newValues, values)
+		r.Header[key] = newValues
+	}
+
+	return r
+}