Merge pull request #6 from rebuy-de/add-env

add environment variables

cmd/command.go

@@ -3,9 +3,12 @@ package cmd
 import (
 	"fmt"
 	"net/http"
+	"os"
+	"strings"
 
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 )
 
 func NewRootCommand() *cobra.Command {
@@ -20,36 +23,61 @@ func NewRootCommand() *cobra.Command {
 		},
 	}
 
-	cmd.PersistentFlags().StringVarP(
-		&app.configPath, "config-path", "c", "./merger.yaml",
-		"Path to the configuration file.")
-	cmd.PersistentFlags().IntVar(
-		&app.port, "listen-port", 8080,
-		"Listen port for the HTTP server.")
+	app.Bind(cmd)
 
 	cmd.AddCommand(NewVersionCommand())
 
 	return cmd
 }
 
 type App struct {
-	configPath string
-	port       int
+	viper *viper.Viper
 }
 
-func (app *App) run(cmd *cobra.Command, args []string) {
-	config, err := ReadConfig(app.configPath)
-	if err != nil {
-		log.WithField("error", err).Error("failed to load config")
-		return
-	}
+func (app *App) Bind(cmd *cobra.Command) {
+	app.viper = viper.New()
+	app.viper.SetEnvPrefix("MERGER")
+	app.viper.AutomaticEnv()
+
+	configPath := cmd.PersistentFlags().StringP(
+		"config-path", "c", "",
+		"Path to the configuration file.")
+	cobra.OnInitialize(func() {
+		if configPath != nil && *configPath != "" {
+			config, err := ReadConfig(*configPath)
+			if err != nil {
+				log.WithField("error", err).Errorf("failed to load config file '%s'", *configPath)
+				os.Exit(1)
+				return
+			}
 
+			urls := []string{}
+			for _, e := range config.Exporters {
+				urls = append(urls, e.URL)
+			}
+			app.viper.SetDefault("urls", strings.Join(urls, " "))
+		}
+	})
+
+	cmd.PersistentFlags().Int(
+		"listen-port", 8080,
+		"Listen port for the HTTP server. (ENV:MERGER_PORT)")
+	app.viper.BindPFlag("port", cmd.PersistentFlags().Lookup("listen-port"))
+
+	cmd.PersistentFlags().StringSlice(
+		"url", nil,
+		"URL to scrape. Can be speficied multiple times. (ENV:MERGER_URLS,space-seperated)")
+	app.viper.BindPFlag("urls", cmd.PersistentFlags().Lookup("url"))
+}
+
+func (app *App) run(cmd *cobra.Command, args []string) {
 	http.Handle("/metrics", Handler{
-		Config: *config,
+		Exporters: app.viper.GetStringSlice("urls"),
 	})
 
-	log.Infof("starting HTTP server on port %d", app.port)
-	err = http.ListenAndServe(fmt.Sprintf(":%d", app.port), nil)
+	port := app.viper.GetInt("port")
+	log.Infof("starting HTTP server on port %d", port)
+	err := http.ListenAndServe(fmt.Sprintf(":%d", port), nil)
 	if err != nil {
 		log.Fatal(err)
 	}

cmd/handler.go

@@ -11,7 +11,7 @@ import (
 )
 
 type Handler struct {
-	Config Config
+	Exporters []string
 }
 
 func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -30,8 +30,9 @@ func (h Handler) Merge(w io.Writer) error {
 	mfs := map[string]*prom.MetricFamily{}
 	tp := new(expfmt.TextParser)
 
-	for _, e := range h.Config.Exporters {
-		resp, err := http.Get(e.URL)
+	for _, url := range h.Exporters {
+		log.WithField("url", url).Debug("getting remote metrics")
+		resp, err := http.Get(url)
 		if err != nil {
 			return err
 		}

cmd/handler_test.go

@@ -11,16 +11,14 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-func testExporter(t testing.TB, content string) (cmd.Exporter, func()) {
+func testExporter(t testing.TB, content string) (string, func()) {
 	t.Helper()
 
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintln(w, content)
 	}))
 
-	return cmd.Exporter{
-		URL: ts.URL,
-	}, ts.Close
+	return ts.URL, ts.Close
 }
 
 func TestHandler(t *testing.T) {
@@ -34,15 +32,13 @@ func TestHandler(t *testing.T) {
 		"bar{} 4\nconflict 5\nshared{meh=\"b\"} 6")
 	defer deferrer()
 
-	config := cmd.Config{
-		Exporters: []cmd.Exporter{
-			te1,
-			te2,
-		},
+	exporters := []string{
+		te1,
+		te2,
 	}
 
 	server := httptest.NewServer(cmd.Handler{
-		Config: config,
+		Exporters: exporters,
 	})
 	defer server.Close()