Skip metrics collect on first pass and more unit tests

internal/metrics/exporter.go

@@ -30,14 +30,16 @@ const (
 )
 
 type exporter struct {
-	qmName   string
-	gaugeMap map[string]*prometheus.GaugeVec
+	qmName       string
+	gaugeMap     map[string]*prometheus.GaugeVec
+	firstCollect bool
 }
 
 func newExporter(qmName string) *exporter {
 	return &exporter{
-		qmName:   qmName,
-		gaugeMap: make(map[string]*prometheus.GaugeVec),
+		qmName:       qmName,
+		gaugeMap:     make(map[string]*prometheus.GaugeVec),
+		firstCollect: true,
 	}
 }
 
@@ -71,17 +73,24 @@ func (e *exporter) Collect(ch chan<- prometheus.Metric) {
 		gaugeVec.Reset()
 
 		// Populate Prometheus Gauge with metric values
-		for label, value := range metric.values {
-			if label == qmgrLabelValue {
-				gaugeVec.WithLabelValues(e.qmName).Set(value)
-			} else {
-				gaugeVec.WithLabelValues(label, e.qmName).Set(value)
+		// - Skip on first collect to avoid build-up of accumulated values
+		if !e.firstCollect {
+			for label, value := range metric.values {
+				if label == qmgrLabelValue {
+					gaugeVec.WithLabelValues(e.qmName).Set(value)
+				} else {
+					gaugeVec.WithLabelValues(label, e.qmName).Set(value)
+				}
 			}
 		}
 
 		// Collect metric
 		gaugeVec.Collect(ch)
 	}
+
+	if e.firstCollect {
+		e.firstCollect = false
+	}
 }
 
 // createGaugeVec returns a Prometheus GaugeVec populated with metric details

internal/metrics/exporter_test.go

@@ -17,10 +17,88 @@ package metrics
 
 import (
 	"testing"
+	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
 )
 
+func TestDescribe(t *testing.T) {
+
+	teardownTestCase := setupTestCase()
+	defer teardownTestCase()
+
+	ch := make(chan *prometheus.Desc)
+	go func() {
+		exporter := newExporter("qmName")
+		exporter.Describe(ch)
+	}()
+
+	collect := <-requestChannel
+	if collect {
+		t.Errorf("Received unexpected collect request")
+	}
+
+	metrics := initialiseMetrics()
+	responseChannel <- metrics
+
+	select {
+	case prometheusDesc := <-ch:
+		expected := "Desc{fqName: \"ibmmq_qmgr_Element1Name\", help: \"Element1Description\", constLabels: {}, variableLabels: [qmgr]}"
+		actual := prometheusDesc.String()
+		if actual != expected {
+			t.Errorf("Expected value=%s; actual %s", expected, actual)
+		}
+	case <-time.After(1 * time.Second):
+		t.Error("Did not receive channel response from describe")
+	}
+}
+
+func TestCollect(t *testing.T) {
+
+	teardownTestCase := setupTestCase()
+	defer teardownTestCase()
+
+	exporter := newExporter("qmName")
+	exporter.gaugeMap["ClassName/Type1Name/Element1Name"] = createGaugeVec("Element1Name", "Element1Description", false)
+
+	for i := 1; i <= 3; i++ {
+
+		ch := make(chan prometheus.Metric)
+		go func() {
+			exporter.Collect(ch)
+			close(ch)
+		}()
+
+		collect := <-requestChannel
+		if !collect {
+			t.Errorf("Received unexpected describe request")
+		}
+
+		populateTestMetrics(i)
+		metrics := initialiseMetrics()
+		updateMetrics(metrics)
+		responseChannel <- metrics
+
+		select {
+		case <-ch:
+			prometheusMetric := dto.Metric{}
+			exporter.gaugeMap["ClassName/Type1Name/Element1Name"].WithLabelValues("qmName").Write(&prometheusMetric)
+			actual := prometheusMetric.GetGauge().GetValue()
+
+			if i == 1 {
+				if actual != float64(0) {
+					t.Errorf("Expected values to be zero on first collect; actual %f", actual)
+				}
+			} else if actual != float64(i) {
+				t.Errorf("Expected value=%f; actual %f", float64(i), actual)
+			}
+		case <-time.After(1 * time.Second):
+			t.Error("Did not receive channel response from collect")
+		}
+	}
+}
+
 func TestCreateGaugeVec(t *testing.T) {
 
 	ch := make(chan *prometheus.Desc)

internal/metrics/update_test.go

@@ -55,6 +55,39 @@ func TestInitialiseMetrics(t *testing.T) {
 	}
 }
 
+func TestUpdateMetrics(t *testing.T) {
+
+	teardownTestCase := setupTestCase()
+	defer teardownTestCase()
+
+	metrics := initialiseMetrics()
+	updateMetrics(metrics)
+
+	metric, _ := metrics["ClassName/Type1Name/Element1Name"]
+	actual, ok := metric.values[qmgrLabelValue]
+
+	if !ok {
+		t.Error("No metric values found for queue manager label")
+	} else {
+		if actual != float64(1) {
+			t.Errorf("Expected metric value=%f; actual %f", float64(1), actual)
+		}
+		if len(metric.values) != 1 {
+			t.Errorf("Expected values-size=%d; actual %d", 1, len(metric.values))
+		}
+	}
+
+	if len(mqmetric.Metrics.Classes[0].Types[0].Elements[0].Values) != 0 {
+		t.Error("Unexpected cached value; publication data should have been reset")
+	}
+
+	updateMetrics(metrics)
+
+	if len(metric.values) != 0 {
+		t.Errorf("Unexpected metric value; data should have been cleared")
+	}
+}
+
 func TestMakeKey(t *testing.T) {
 
 	teardownTestCase := setupTestCase()
@@ -68,13 +101,13 @@ func TestMakeKey(t *testing.T) {
 }
 
 func setupTestCase() func() {
-	populateTestMetrics()
+	populateTestMetrics(1)
 	return func() {
 		cleanTestMetrics()
 	}
 }
 
-func populateTestMetrics() {
+func populateTestMetrics(testValue int) {
 
 	metricClass := new(mqmetric.MonClass)
 	metricType1 := new(mqmetric.MonType)
@@ -87,8 +120,11 @@ func populateTestMetrics() {
 	metricType2.Name = "Type2Name"
 	metricElement1.MetricName = "Element1Name"
 	metricElement1.Description = "Element1Description"
+	metricElement1.Values = make(map[string]int64)
+	metricElement1.Values[qmgrLabelValue] = int64(testValue)
 	metricElement2.MetricName = "Element2Name"
 	metricElement2.Description = "Element2Description"
+	metricElement2.Values = make(map[string]int64)
 	metricType1.ObjectTopic = "ObjectTopic"
 	metricType2.ObjectTopic = "%s"
 	metricElement1.Parent = metricType1