refactor the code related to xtcp (#3449)

pkg/metrics/mem/server.go

@@ -60,25 +60,30 @@ func (m *serverMetrics) run() {
 	go func() {
 		for {
 			time.Sleep(12 * time.Hour)
-			log.Debug("start to clear useless proxy statistics data...")
-			m.clearUselessInfo()
-			log.Debug("finish to clear useless proxy statistics data")
+			start := time.Now()
+			count, total := m.clearUselessInfo()
+			log.Debug("clear useless proxy statistics data count %d/%d, cost %v", count, total, time.Since(start))
 		}
 	}()
 }
 
-func (m *serverMetrics) clearUselessInfo() {
+func (m *serverMetrics) clearUselessInfo() (int, int) {
+	count := 0
+	total := 0
 	// To check if there are proxies that closed than 7 days and drop them.
 	m.mu.Lock()
 	defer m.mu.Unlock()
+	total = len(m.info.ProxyStatistics)
 	for name, data := range m.info.ProxyStatistics {
 		if !data.LastCloseTime.IsZero() &&
 			data.LastStartTime.Before(data.LastCloseTime) &&
 			time.Since(data.LastCloseTime) > time.Duration(7*24)*time.Hour {
 			delete(m.info.ProxyStatistics, name)
+			count++
 			log.Trace("clear proxy [%s]'s statistics data, lastCloseTime: [%s]", name, data.LastCloseTime.String())
 		}
 	}
+	return count, total
 }
 
 func (m *serverMetrics) NewClient() {