feat(inputs.elasticsearch): Add support for custom headers (#15544)

plugins/inputs/elasticsearch/README.md

@@ -46,6 +46,9 @@ See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
   ## servers = ["http://user:pass@localhost:9200"]
   servers = ["http://localhost:9200"]
 
+  ## HTTP headers to send with each request
+  # headers = { "X-Custom-Header" = "Custom" }
+
   ## Timeout for HTTP requests to the elastic search server(s)
   ## deprecated in 1.29.0; use 'timeout' instead
   http_timeout = "5s"

plugins/inputs/elasticsearch/elasticsearch.go

@@ -98,6 +98,7 @@ type indexStat struct {
 type Elasticsearch struct {
 	Local                      bool              `toml:"local"`
 	Servers                    []string          `toml:"servers"`
+	HTTPHeaders                map[string]string `toml:"headers"`
 	HTTPTimeout                config.Duration   `toml:"http_timeout" deprecated:"1.29.0;1.35.0;use 'timeout' instead"`
 	ClusterHealth              bool              `toml:"cluster_health"`
 	ClusterHealthLevel         string            `toml:"cluster_health_level"`
@@ -641,6 +642,10 @@ func (e *Elasticsearch) getCatMaster(url string) (string, error) {
 		req.SetBasicAuth(e.Username, e.Password)
 	}
 
+	for key, value := range e.HTTPHeaders {
+		req.Header.Add(key, value)
+	}
+
 	r, err := e.client.Do(req)
 	if err != nil {
 		return "", err
@@ -677,6 +682,10 @@ func (e *Elasticsearch) gatherJSONData(url string, v interface{}) error {
 		req.SetBasicAuth(e.Username, e.Password)
 	}
 
+	for key, value := range e.HTTPHeaders {
+		req.Header.Add(key, value)
+	}
+
 	r, err := e.client.Do(req)
 	if err != nil {
 		return err

plugins/inputs/elasticsearch/sample.conf

@@ -5,6 +5,9 @@
   ## servers = ["http://user:pass@localhost:9200"]
   servers = ["http://localhost:9200"]
 
+  ## HTTP headers to send with each request
+  # headers = { "X-Custom-Header" = "Custom" }
+
   ## Timeout for HTTP requests to the elastic search server(s)
   ## deprecated in 1.29.0; use 'timeout' instead
   http_timeout = "5s"