Add the ability to use ApiKey based authentication

README.md

@@ -56,6 +56,7 @@ elasticsearch_exporter --help
 | es.client-cert          | 1.0.2                 | Path to PEM file that contains the corresponding cert for the private key to connect to Elasticsearch. | |
 | es.clusterinfo.interval | 1.1.0rc1              |  Cluster info update interval for the cluster label | 5m |
 | es.ssl-skip-verify      | 1.0.4rc1              | Skip SSL verification when connecting to Elasticsearch. | false |
+| es.apiKey               | unreleased            | API Key to use for authenticating against Elasticsearch. |  |
 | web.listen-address      | 1.0.2                 | Address to listen on for web interface and telemetry. | :9114 |
 | web.telemetry-path      | 1.0.2                 | Path under which to expose metrics. | /metrics |
 | version                 | 1.0.2                 | Show version info on stdout and exit. | |

main.go

@@ -14,6 +14,7 @@
 package main
 
 import (
+	"fmt"
 	"net/http"
 	"net/url"
 	"os"
@@ -31,6 +32,16 @@ import (
 	"gopkg.in/alecthomas/kingpin.v2"
 )
 
+type transportWithApiKey struct {
+	underlyingTransport http.RoundTripper
+	apiKey              string
+}
+
+func (t *transportWithApiKey) RoundTrip(req *http.Request) (*http.Response, error) {
+	req.Header.Add("Authorization", fmt.Sprintf("ApiKey %s", t.apiKey))
+	return t.underlyingTransport.RoundTrip(req)
+}
+
 func main() {
 	var (
 		Name          = "elasticsearch_exporter"
@@ -85,6 +96,9 @@ func main() {
 		esInsecureSkipVerify = kingpin.Flag("es.ssl-skip-verify",
 			"Skip SSL verification when connecting to Elasticsearch.").
 			Default("false").Envar("ES_SSL_SKIP_VERIFY").Bool()
+		esApiKey = kingpin.Flag("es.apiKey",
+			"API Key to use for authenticating against Elasticsearch").
+			Default("").Envar("ES_API_KEY").String()
 		logLevel = kingpin.Flag("log.level",
 			"Sets the loglevel. Valid levels are debug, info, warn, error").
 			Default("info").Envar("LOG_LEVEL").String()
@@ -114,12 +128,25 @@ func main() {
 	// returns nil if not provided and falls back to simple TCP.
 	tlsConfig := createTLSConfig(*esCA, *esClientCert, *esClientPrivateKey, *esInsecureSkipVerify)
 
+	var httpTransport http.RoundTripper
+
+	httpTransport = &http.Transport{
+		TLSClientConfig: tlsConfig,
+		Proxy:           http.ProxyFromEnvironment,
+	}
+
+	if *esApiKey != "" {
+		apiKey := *esApiKey
+
+		httpTransport = &transportWithApiKey{
+			underlyingTransport: httpTransport,
+			apiKey:              apiKey,
+		}
+	}
+
 	httpClient := &http.Client{
-		Timeout: *esTimeout,
-		Transport: &http.Transport{
-			TLSClientConfig: tlsConfig,
-			Proxy:           http.ProxyFromEnvironment,
-		},
+		Timeout:   *esTimeout,
+		Transport: httpTransport,
 	}
 
 	// version metric