[#164] Add tracing attributes

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

cmd/http-gw/settings.go

@@ -86,10 +86,11 @@ const (
 	cfgPprofAddress      = "pprof.address"
 
 	// Tracing ...
-	cfgTracingEnabled   = "tracing.enabled"
-	cfgTracingExporter  = "tracing.exporter"
-	cfgTracingEndpoint  = "tracing.endpoint"
-	cfgTracingTrustedCa = "tracing.trusted_ca"
+	cfgTracingEnabled    = "tracing.enabled"
+	cfgTracingExporter   = "tracing.exporter"
+	cfgTracingEndpoint   = "tracing.endpoint"
+	cfgTracingTrustedCa  = "tracing.trusted_ca"
+	cfgTracingAttributes = "tracing.attributes"
 
 	// Pool config.
 	cfgConTimeout         = "connect_timeout"
@@ -790,3 +791,27 @@ func fetchMultinetConfig(v *viper.Viper, l *zap.Logger) (cfg internalnet.Config)
 
 	return
 }
+
+func fetchTracingAttributes(v *viper.Viper) (map[string]string, error) {
+	attributes := make(map[string]string)
+	for i := 0; ; i++ {
+		key := cfgTracingAttributes + "." + strconv.Itoa(i) + "."
+		attrKey := v.GetString(key + "key")
+		attrValue := v.GetString(key + "value")
+		if attrKey == "" {
+			break
+		}
+
+		if _, ok := attributes[attrKey]; ok {
+			return nil, fmt.Errorf("tracing attribute key %s defined more than once", attrKey)
+		}
+
+		if attrValue == "" {
+			return nil, fmt.Errorf("empty tracing attribute value for key %s", attrKey)
+		}
+
+		attributes[attrKey] = attrValue
+	}
+
+	return attributes, nil
+}