feat(inputs.prometheus): Add support for custom header (#12050)

plugins/inputs/prometheus/README.md

@@ -98,6 +98,9 @@ See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
   # username = ""
   # password = ""
 
+  ## Optional custom HTTP headers
+  # headers = {"X-Special-Header" = "Special-Value"}
+
   ## Specify timeout duration for slower prometheus clients (default is 3s)
   # response_timeout = "3s"
 

plugins/inputs/prometheus/prometheus.go

@@ -58,6 +58,8 @@ type Prometheus struct {
 	Username string `toml:"username"`
 	Password string `toml:"password"`
 
+	HTTPHeaders map[string]string `toml:"http_headers"`
+
 	ResponseTimeout config.Duration `toml:"response_timeout"`
 
 	MetricVersion int `toml:"metric_version"`
@@ -298,6 +300,12 @@ func (p *Prometheus) gatherURL(u URLAndAddress, acc telegraf.Accumulator) error
 		req.SetBasicAuth(p.Username, p.Password)
 	}
 
+	if p.HTTPHeaders != nil {
+		for key, value := range p.HTTPHeaders {
+			req.Header.Add(key, value)
+		}
+	}
+
 	var resp *http.Response
 	if u.URL.Scheme != "unix" {
 		//nolint:bodyclose // False positive (because of if-else) - body will be closed in `defer`

plugins/inputs/prometheus/sample.conf

@@ -81,6 +81,9 @@
   # username = ""
   # password = ""
 
+  ## Optional custom HTTP headers
+  # headers = {"X-Special-Header" = "Special-Value"}
+
   ## Specify timeout duration for slower prometheus clients (default is 3s)
   # response_timeout = "3s"