[#1690] qos: Do not export zero metrics counters

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

internal/qos/limiter.go

@@ -211,13 +211,26 @@ func (n *mClockLimiter) startMetricsCollect() {
 					continue
 				}
 				metrics := n.metrics.Load().metrics
-				for tag, s := range n.readStats {
-					metrics.SetOperationTagCounters(shardID, "read", tag, s.pending.Load(), s.inProgress.Load(), s.completed.Load(), s.resourceExhausted.Load())
-				}
-				for tag, s := range n.writeStats {
-					metrics.SetOperationTagCounters(shardID, "write", tag, s.pending.Load(), s.inProgress.Load(), s.completed.Load(), s.resourceExhausted.Load())
-				}
+				exportMetrics(metrics, n.readStats, shardID, "read")
+				exportMetrics(metrics, n.writeStats, shardID, "write")
 			}
 		}
 	}()
 }
+
+func exportMetrics(metrics Metrics, stats map[string]*stat, shardID, operation string) {
+	var pending uint64
+	var inProgress uint64
+	var completed uint64
+	var resExh uint64
+	for tag, s := range stats {
+		pending = s.pending.Load()
+		inProgress = s.inProgress.Load()
+		completed = s.completed.Load()
+		resExh = s.resourceExhausted.Load()
+		if pending == 0 && inProgress == 0 && completed == 0 && resExh == 0 {
+			continue
+		}
+		metrics.SetOperationTagCounters(shardID, operation, tag, pending, inProgress, completed, resExh)
+	}
+}