Make the flags configurable using environment variables

Gopkg.toml

@@ -0,0 +1,4 @@
+
+[[constraint]]
+  name = "github.com/peterbourgon/ff"
+  version = "1.2.0"

README.md

@@ -12,23 +12,34 @@ To run it:
 ./clickhouse_exporter [flags]
 ```
 
-Help on flags:
+Flags are also configurable using environment variables. See the usage with:
+
 ```bash
 ./clickhouse_exporter --help
 ```
 
-Credentials(if not default):
-
-via environment variables
 ```
-CLICKHOUSE_USER
-CLICKHOUSE_PASSWORD
+Usage of clickhouse-exporter:
+  -insecure
+    	Ignore server certificate if using https. Override environment (CLICKHOUSE_INSECURE) (default true)
+  -password string
+    	Clickhouse password. Override environment (CLICKHOUSE_PASSWORD)
+  -scrape_uri string
+    	URI to clickhouse http endpoint. Override environment (CLICKHOUSE_SCRAPE_URI) (default "http://localhost:8123/")
+  -telemetry.address string
+    	Address on which to expose metrics. Override environment (CLICKHOUSE_TELEMETRY_ADDRESS) (default ":9116")
+  -telemetry.endpoint string
+    	Path under which to expose metrics. Override environment (CLICKHOUSE_TELEMETRY_ENDPOINT) (default "/metrics")
+  -user string
+    	Clickhouse user. Override environment (CLICKHOUSE_USER)
 ```
 
 ## Using Docker
 
 ```
 docker run -d -p 9116:9116 f1yegor/clickhouse-exporter -scrape_uri=http://clickhouse.service.consul:8123/
 ```
+
 ## Sample dashboard
+
 Grafana dashboard could be a start for inspiration https://grafana.net/dashboards/882

clickhouse_exporter.go

@@ -7,28 +7,32 @@ import (
 	"os"
 
 	"github.com/f1yegor/clickhouse_exporter/exporter"
+	"github.com/peterbourgon/ff"
 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/log"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/prometheus/log"
 )
 
 var (
-	listeningAddress    = flag.String("telemetry.address", ":9116", "Address on which to expose metrics.")
-	metricsEndpoint     = flag.String("telemetry.endpoint", "/metrics", "Path under which to expose metrics.")
-	clickhouseScrapeURI = flag.String("scrape_uri", "http://localhost:8123/", "URI to clickhouse http endpoint")
-	insecure            = flag.Bool("insecure", true, "Ignore server certificate if using https")
-	user                = os.Getenv("CLICKHOUSE_USER")
-	password            = os.Getenv("CLICKHOUSE_PASSWORD")
+	fs                  = flag.NewFlagSet("clickhouse-exporter", flag.ExitOnError)
+	listeningAddress    = fs.String("telemetry.address", ":9116", "Address on which to expose metrics. Override environment (CLICKHOUSE_TELEMETRY_ADDRESS)")
+	metricsEndpoint     = fs.String("telemetry.endpoint", "/metrics", "Path under which to expose metrics. Override environment (CLICKHOUSE_TELEMETRY_ENDPOINT)")
+	clickhouseScrapeURI = fs.String("scrape_uri", "http://localhost:8123/", "URI to clickhouse http endpoint. Override environment (CLICKHOUSE_SCRAPE_URI)")
+	insecure            = fs.Bool("insecure", true, "Ignore server certificate if using https. Override environment (CLICKHOUSE_INSECURE)")
+	user                = fs.String("user", "", "Clickhouse user. Override environment (CLICKHOUSE_USER)")
+	password            = fs.String("password", "", "Clickhouse password. Override environment (CLICKHOUSE_PASSWORD)")
 )
 
 func main() {
-	flag.Parse()
+	if err := ff.Parse(fs, os.Args[1:], ff.WithEnvVarPrefix("CLICKHOUSE")); err != nil {
+		panic(err)
+	}
 
 	uri, err := url.Parse(*clickhouseScrapeURI)
 	if err != nil {
 		log.Fatal(err)
 	}
-	e := exporter.NewExporter(*uri, *insecure, user, password)
+	e := exporter.NewExporter(*uri, *insecure, *user, *password)
 	prometheus.MustRegister(e)
 
 	log.Printf("Starting Server: %s", *listeningAddress)