app/vmagent: initial implementation for vmagent

lib/httpserver/metrics.go

@@ -23,13 +23,11 @@ func WritePrometheusMetrics(w io.Writer) {
 	fmt.Fprintf(w, "vm_app_start_timestamp %d\n", startTime.Unix())
 	fmt.Fprintf(w, "vm_app_uptime_seconds %d\n", int(time.Since(startTime).Seconds()))
 
-	// TODO: export other interesting stuff.
-
 	// Export flags as metrics.
 	flag.VisitAll(func(f *flag.Flag) {
 		lname := strings.ToLower(f.Name)
 		value := f.Value.String()
-		if strings.Contains(lname, "pass") || strings.Contains(lname, "key") || strings.Contains(lname, "secret") {
+		if isSecretFlag(lname) {
 			// Do not expose passwords and keys to prometheus.
 			value = "secret"
 		}
@@ -38,3 +36,23 @@ func WritePrometheusMetrics(w io.Writer) {
 }
 
 var startTime = time.Now()
+
+// RegisterSecretFlag registers flagName as secret.
+//
+// This function must be called before starting httpserver.
+// It cannot be called from concurrent goroutines.
+//
+// Secret flags aren't exported at `/metrics` page.
+func RegisterSecretFlag(flagName string) {
+	lname := strings.ToLower(flagName)
+	secretFlags[lname] = true
+}
+
+var secretFlags = make(map[string]bool)
+
+func isSecretFlag(s string) bool {
+	if strings.Contains(s, "pass") || strings.Contains(s, "key") || strings.Contains(s, "secret") || strings.Contains(s, "token") {
+		return true
+	}
+	return secretFlags[s]
+}