set user agent on scrape requests to nginx

exporter.go

@@ -233,9 +233,15 @@ func main() {
  scrapeURI = &newScrapeURI
  }
 
+ userAgent := fmt.Sprintf("NGINX-Prometheus-Exporter/v%v", version)
+ userAgentRT := &userAgentRoundTripper{
+ agent: userAgent,
+ rt: transport,
+ }
+
  httpClient := &http.Client{
  Timeout: timeout.Duration,
- Transport: transport,
+ Transport: userAgentRT,
  }
 
  srv := http.Server{}
@@ -290,3 +296,28 @@ func main() {
  log.Printf("NGINX Prometheus Exporter has successfully started")
  log.Fatal(srv.Serve(listener))
 }
+
+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)
+ *r = *req // shallow clone
+
+ // 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
+}