remove resetStats from GatherOnce

When the measruement tries to gather attached metrics is using the
GatherOnce function which was resetting measurement stats

This behaviour was causing that filter or other stats could be removed
based on the order of execution.

This PR removes the ResetStats call to delegate into the upper function
in order to control and manage stats behaviour, fixes #514

pkg/data/measurement/measurement.go

@@ -964,6 +964,7 @@ func (m *Measurement) GatherLoop(
 				// If connection and initialization are correct, mark the measurement as initiliazed and gather data for the first time
 				// Set influxClient as nil, the first time it shouldn't send metrics
 				m.initialized = true
+				m.stats.ResetCounters()
 				err := m.GatherOnce(gatherLock, varMap, tagMap, nil)
 				if err != nil {
 					// if error is because of no response from any metric
@@ -985,12 +986,6 @@ func (m *Measurement) GatherLoop(
 	}
 	utils.WaitAlignForNextCycle(gatherFreq, m.Log)
 
-	// Gather ticker initialization and stats
-	gatherTicker := time.NewTicker(time.Duration(gatherFreq) * time.Second)
-	defer gatherTicker.Stop()
-	m.stats.GatherFreq = gatherFreq
-	m.stats.SetGatherNextTime(time.Now().Add(time.Duration(gatherFreq) * time.Second).Unix())
-
 	// Filter ticker initialization and stats
 	// Measurement Filter Freq overrides Device Filter Freq (creating ticker)
 	filterFreq := gatherFreq * deviceUpdateFilterFreq
@@ -1011,6 +1006,12 @@ func (m *Measurement) GatherLoop(
 		defer updateFilterTicker.Stop()
 	}
 
+	// Gather ticker initialization and stats
+	gatherTicker := time.NewTicker(time.Duration(gatherFreq) * time.Second)
+	defer gatherTicker.Stop()
+	m.stats.GatherFreq = gatherFreq
+	m.stats.SetGatherNextTime(time.Now().Add(time.Duration(gatherFreq) * time.Second).Unix())
+
 	for {
 		m.Log.Info("MeasurementLoop new Iteration")
 		// In each iteration, if measurement is enabled and not connected, try again to connect
@@ -1035,6 +1036,7 @@ func (m *Measurement) GatherLoop(
 				// If connection and initialization are correct, mark the measurement as initialized and gather data for the first time
 				m.initialized = true
 				// Set influxClient as nil, the first time it shouldn't send metrics
+				m.stats.ResetCounters()
 				err := m.GatherOnce(gatherLock, varMap, tagMap, nil)
 				if err != nil {
 					// if error is because of no response from any metric
@@ -1047,12 +1049,18 @@ func (m *Measurement) GatherLoop(
 		}
 		m.stats.SetStatus(m.Active, m.Connected)
 		select {
-		case <-updateFilterTicker.C:
-			// compute next filter time ( needed to show in the UI )
-			m.stats.SetFilterNextTime(time.Now().Add(time.Duration(filterFreq) * time.Second).Unix())
-			// filter
-			m.filterUpdate()
 		case <-gatherTicker.C:
+			// we reset counter to start a clear stats counter iteration
+			// and ensure that he filters is always 0
+			m.stats.ResetCounters()
+			// check if we need to update the filters based on the ticker
+			select {
+			case <-updateFilterTicker.C:
+				m.stats.SetFilterNextTime(time.Now().Add(time.Duration(filterFreq) * time.Second).Unix())
+				m.filterUpdate()
+			default:
+				m.Log.Debugf("No filter ticker received")
+			}
 			// compute next gather time ( needed to show in the UI )
 			m.stats.SetGatherNextTime(time.Now().Add(time.Duration(gatherFreq) * time.Second).Unix())
 			// Gather
@@ -1077,6 +1085,7 @@ func (m *Measurement) GatherLoop(
 			case bus.FilterUpdate:
 				m.filterUpdate()
 			case bus.ForceGather:
+				m.stats.ResetCounters()
 				m.GatherOnce(gatherLock, varMap, tagMap, influxClient)
 			case bus.Enabled:
 				active, ok := val.Data.(bool)
@@ -1215,7 +1224,6 @@ func (m *Measurement) GatherOnce(
 	// Do not gather data if measurement is disabled or it doesn't have a connection or measurement is not initialized
 	if !m.Active || !m.Connected || !m.initialized {
 		m.Log.Infof("Skip measurement Gathering process Active[%t],Connected[%t],Initialized[%t]", m.Active, m.Connected, m.initialized)
-		m.stats.ResetCounters()
 		m.statsData.Lock()
 		m.Stats = m.getBasicStats()
 		m.statsData.Unlock()
@@ -1231,7 +1239,6 @@ func (m *Measurement) GatherOnce(
 	// Mark previous values as old so we can know if new metrics
 	// have been gathered
 	m.InvalidateMetrics()
-	m.stats.ResetCounters()
 
 	m.Log.Debugf("-------Processing measurement : %s", m.ID)