diff --git a/ginmetrics/middleware.go b/ginmetrics/middleware.go
index 20eb8fb..efae0b9 100644
--- a/ginmetrics/middleware.go
+++ b/ginmetrics/middleware.go
@@ -59,47 +59,98 @@ func (m *Monitor) initGinMetrics() {
 		Type:        Counter,
 		Name:        metricRequestTotal,
 		Description: "all the server received request num.",
-		Labels:      nil,
+		Labels:      m.getMetricLabelsIncludingMetadata(metricRequestTotal),
 	})
 	_ = monitor.AddMetric(&Metric{
 		Type:        Counter,
 		Name:        metricRequestUVTotal,
 		Description: "all the server received ip num.",
-		Labels:      nil,
+		Labels:      m.getMetricLabelsIncludingMetadata(metricRequestUVTotal),
 	})
 	_ = monitor.AddMetric(&Metric{
 		Type:        Counter,
 		Name:        metricURIRequestTotal,
 		Description: "all the server received request num with every uri.",
-		Labels:      []string{"uri", "method", "code"},
+		Labels:      m.getMetricLabelsIncludingMetadata(metricURIRequestTotal),
 	})
 	_ = monitor.AddMetric(&Metric{
 		Type:        Counter,
 		Name:        metricRequestBody,
 		Description: "the server received request body size, unit byte",
-		Labels:      nil,
+		Labels:      m.getMetricLabelsIncludingMetadata(metricRequestBody),
 	})
 	_ = monitor.AddMetric(&Metric{
 		Type:        Counter,
 		Name:        metricResponseBody,
 		Description: "the server send response body size, unit byte",
-		Labels:      nil,
+		Labels:      m.getMetricLabelsIncludingMetadata(metricResponseBody),
 	})
 	_ = monitor.AddMetric(&Metric{
 		Type:        Histogram,
 		Name:        metricRequestDuration,
 		Description: "the time server took to handle the request.",
-		Labels:      []string{"uri"},
+		Labels:      m.getMetricLabelsIncludingMetadata(metricRequestDuration),
 		Buckets:     m.reqDuration,
 	})
 	_ = monitor.AddMetric(&Metric{
 		Type:        Counter,
 		Name:        metricSlowRequest,
 		Description: fmt.Sprintf("the server handled slow requests counter, t=%d.", m.slowTime),
-		Labels:      []string{"uri", "method", "code"},
+		Labels:      m.getMetricLabelsIncludingMetadata(metricSlowRequest),
 	})
 }
 
+func (m *Monitor) includesMetadata() bool {
+	return len(m.metadata) > 0
+}
+
+func (m *Monitor) getMetadata() ([]string, []string) {
+	metadata_labels := []string{}
+	metadata_values := []string{}
+
+	for v := range m.metadata {
+		metadata_labels = append(metadata_labels, v)
+		metadata_values = append(metadata_values, m.metadata[v])
+	}
+
+	return metadata_labels, metadata_values
+}
+
+func (m *Monitor) getMetricLabelsIncludingMetadata(metricName string) []string {
+	includes_metadata := m.includesMetadata()
+	metadata_labels, _ := m.getMetadata()
+
+	switch metricName {
+	case metricRequestDuration:
+		metric_labels := []string{"uri"}
+		if includes_metadata {
+			metric_labels = append(metric_labels, metadata_labels...)
+		}
+		return metric_labels
+
+	case metricURIRequestTotal:
+		metric_labels := []string{"uri", "method", "code"}
+		if includes_metadata {
+			metric_labels = append(metric_labels, metadata_labels...)
+		}
+		return metric_labels
+
+	case metricSlowRequest:
+		metric_labels := []string{"uri", "method", "code"}
+		if includes_metadata {
+			metric_labels = append(metric_labels, metadata_labels...)
+		}
+		return metric_labels
+
+	default:
+		var metric_labels []string = nil
+		if includes_metadata {
+			metric_labels = metadata_labels
+		}
+		return metric_labels
+	}
+}
+
 // monitorInterceptor as gin monitor middleware.
 func (m *Monitor) monitorInterceptor(ctx *gin.Context) {
 	// some paths should not be reported
@@ -122,34 +173,50 @@ func (m *Monitor) ginMetricHandle(ctx *gin.Context, start time.Time) {
 	w := ctx.Writer
 
 	// set request total
-	_ = m.GetMetric(metricRequestTotal).Inc(nil)
+	var metric_values []string = nil
+	_ = m.GetMetric(metricRequestTotal).Inc(m.getMetricValues(metric_values))
 
 	// set uv
 	if clientIP := ctx.ClientIP(); !bloomFilter.Contains(clientIP) {
 		bloomFilter.Add(clientIP)
-		_ = m.GetMetric(metricRequestUVTotal).Inc(nil)
+		metric_values = nil
+		_ = m.GetMetric(metricRequestUVTotal).Inc(m.getMetricValues(metric_values))
 	}
 
 	// set uri request total
-	_ = m.GetMetric(metricURIRequestTotal).Inc([]string{ctx.FullPath(), r.Method, strconv.Itoa(w.Status())})
+	metric_values = []string{ctx.FullPath(), r.Method, strconv.Itoa(w.Status())}
+	_ = m.GetMetric(metricURIRequestTotal).Inc(m.getMetricValues(metric_values))
 
 	// set request body size
 	// since r.ContentLength can be negative (in some occasions) guard the operation
 	if r.ContentLength >= 0 {
-		_ = m.GetMetric(metricRequestBody).Add(nil, float64(r.ContentLength))
+		metric_values = nil
+		_ = m.GetMetric(metricRequestBody).Add(m.getMetricValues(metric_values), float64(r.ContentLength))
 	}
 
 	// set slow request
 	latency := time.Since(start)
 	if int32(latency.Seconds()) > m.slowTime {
-		_ = m.GetMetric(metricSlowRequest).Inc([]string{ctx.FullPath(), r.Method, strconv.Itoa(w.Status())})
+		metric_values = []string{ctx.FullPath(), r.Method, strconv.Itoa(w.Status())}
+		_ = m.GetMetric(metricSlowRequest).Inc(m.getMetricValues(metric_values))
 	}
 
 	// set request duration
-	_ = m.GetMetric(metricRequestDuration).Observe([]string{ctx.FullPath()}, latency.Seconds())
+	metric_values = []string{ctx.FullPath()}
+	_ = m.GetMetric(metricRequestDuration).Observe(m.getMetricValues(metric_values), latency.Seconds())
 
 	// set response size
 	if w.Size() > 0 {
-		_ = m.GetMetric(metricResponseBody).Add(nil, float64(w.Size()))
+		metric_values = nil
+		_ = m.GetMetric(metricResponseBody).Add(m.getMetricValues(metric_values), float64(w.Size()))
+	}
+}
+
+func (m *Monitor) getMetricValues(metric_values []string) []string {
+	includes_metadata := m.includesMetadata()
+	_, metadata_values := m.getMetadata()
+	if includes_metadata {
+		metric_values = append(metric_values, metadata_values...)
 	}
+	return metric_values
 }
diff --git a/ginmetrics/types.go b/ginmetrics/types.go
index 1444dd0..d284e55 100644
--- a/ginmetrics/types.go
+++ b/ginmetrics/types.go
@@ -38,6 +38,7 @@ type Monitor struct {
 	excludePaths []string
 	reqDuration  []float64
 	metrics      map[string]*Metric
+	metadata     map[string]string
 }
 
 // GetMonitor used to get global Monitor object,
@@ -50,6 +51,7 @@ func GetMonitor() *Monitor {
 			excludePaths: defaultExcludePaths,
 			reqDuration:  defaultDuration,
 			metrics:      make(map[string]*Metric),
+			metadata:     make(map[string]string),
 		}
 	}
 	return monitor