Allow collection of HTTP Headers in http_response input (#7405)

plugins/inputs/http_response/README.md

@@ -47,6 +47,11 @@ This input plugin checks HTTP/HTTPS connections.
   # [inputs.http_response.headers]
   #   Host = "github.com"
 
+  ## Optional setting to map reponse http headers into tags
+  ## If the http header is not present on the request, no corresponding tag will be added
+  ## If multiple instances of the http header are present, only the first value will be used
+  # http_header_tags = {"HTTP_HEADER" = "TAG_NAME"}
+
   ## Interface to use when dialing an address
   # interface = "eth0"
 ```

plugins/inputs/http_response/http_response.go

@@ -27,6 +27,7 @@ type HTTPResponse struct {
 	Body            string
 	Method          string
 	ResponseTimeout internal.Duration
+	HTTPHeaderTags  map[string]string `toml:"http_header_tags"`
 	Headers         map[string]string
 	FollowRedirects bool
 	// Absolute path to file with Bearer token
@@ -98,6 +99,11 @@ var sampleConfig = `
   # [inputs.http_response.headers]
   #   Host = "github.com"
 
+  ## Optional setting to map reponse http headers into tags
+  ## If the http header is not present on the request, no corresponding tag will be added
+  ## If multiple instances of the http header are present, only the first value will be used
+  # http_header_tags = {"HTTP_HEADER" = "TAG_NAME"}
+
   ## Interface to use when dialing an address
   # interface = "eth0"
 `
@@ -265,6 +271,14 @@ func (h *HTTPResponse) httpGather(u string) (map[string]interface{}, map[string]
 	resp, err := h.client.Do(request)
 	response_time := time.Since(start).Seconds()
 
+	// Add the response headers
+	for headerName, tag := range h.HTTPHeaderTags {
+		headerValues, foundHeader := resp.Header[headerName]
+		if foundHeader && len(headerValues) > 0 {
+			tags[tag] = headerValues[0]
+		}
+	}
+
 	// If an error in returned, it means we are dealing with a network error, as
 	// HTTP error codes do not generate errors in the net/http library
 	if err != nil {

plugins/inputs/http_response/http_response_test.go

@@ -86,6 +86,11 @@ func setUpTestMux() http.Handler {
 		http.Redirect(w, req, "/good", http.StatusMovedPermanently)
 	})
 	mux.HandleFunc("/good", func(w http.ResponseWriter, req *http.Request) {
+		w.Header().Set("Server", "MyTestServer")
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, "hit the good page!")
+	})
+	mux.HandleFunc("/noheader", func(w http.ResponseWriter, req *http.Request) {
 		fmt.Fprintf(w, "hit the good page!")
 	})
 	mux.HandleFunc("/jsonresponse", func(w http.ResponseWriter, req *http.Request) {
@@ -218,6 +223,72 @@ func TestFields(t *testing.T) {
 	checkOutput(t, &acc, expectedFields, expectedTags, absentFields, nil)
 }
 
+func TestHTTPHeaderTags(t *testing.T) {
+	mux := setUpTestMux()
+	ts := httptest.NewServer(mux)
+	defer ts.Close()
+
+	h := &HTTPResponse{
+		Log:             testutil.Logger{},
+		Address:         ts.URL + "/good",
+		Body:            "{ 'test': 'data'}",
+		Method:          "GET",
+		ResponseTimeout: internal.Duration{Duration: time.Second * 20},
+		HTTPHeaderTags:  map[string]string{"Server": "my_server", "Content-Type": "content_type"},
+		Headers: map[string]string{
+			"Content-Type": "application/json",
+		},
+		FollowRedirects: true,
+	}
+
+	var acc testutil.Accumulator
+	err := h.Gather(&acc)
+	require.NoError(t, err)
+
+	expectedFields := map[string]interface{}{
+		"http_response_code": http.StatusOK,
+		"result_type":        "success",
+		"result_code":        0,
+		"response_time":      nil,
+		"content_length":     nil,
+	}
+	expectedTags := map[string]interface{}{
+		"server":       nil,
+		"method":       "GET",
+		"status_code":  "200",
+		"result":       "success",
+		"my_server":    "MyTestServer",
+		"content_type": "application/json; charset=utf-8",
+	}
+	absentFields := []string{"response_string_match"}
+	checkOutput(t, &acc, expectedFields, expectedTags, absentFields, nil)
+
+	h = &HTTPResponse{
+		Log:             testutil.Logger{},
+		Address:         ts.URL + "/noheader",
+		Body:            "{ 'test': 'data'}",
+		Method:          "GET",
+		ResponseTimeout: internal.Duration{Duration: time.Second * 20},
+		HTTPHeaderTags:  map[string]string{"Server": "my_server", "Content-Type": "content_type"},
+		Headers: map[string]string{
+			"Content-Type": "application/json",
+		},
+		FollowRedirects: true,
+	}
+
+	acc = testutil.Accumulator{}
+	err = h.Gather(&acc)
+	require.NoError(t, err)
+
+	expectedTags = map[string]interface{}{
+		"server":      nil,
+		"method":      "GET",
+		"status_code": "200",
+		"result":      "success",
+	}
+	checkOutput(t, &acc, expectedFields, expectedTags, absentFields, nil)
+}
+
 func findInterface() (net.Interface, error) {
 	potential, _ := net.Interfaces()