Merge pull request #91 from drawks/issue-88

Resolves #88 - histograms use wrong units

exporter.go

@@ -327,7 +327,7 @@ func (b *Exporter) Listen(e <-chan Events) {
 						mapping,
 					)
 					if err == nil {
-						histogram.Observe(event.Value())
+						histogram.Observe(event.Value() / 1000) // prometheus presumes seconds, statsd millisecond
 						eventStats.WithLabelValues("timer").Inc()
 					} else {
 						log.Errorf(regErrF, metricName, err)

exporter_test.go

@@ -18,6 +18,8 @@ import (
 	"net"
 	"testing"
 	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 // TestNegativeCounter validates when we send a negative
@@ -74,6 +76,45 @@ func TestInvalidUtf8InDatadogTagValue(t *testing.T) {
 	}
 }
 
+type MockHistogram struct {
+	prometheus.Metric
+	prometheus.Collector
+	value float64
+}
+
+func (h *MockHistogram) Observe(n float64) {
+	h.value = n
+}
+
+func TestHistogramUnits(t *testing.T) {
+	events := make(chan Events, 1)
+	name := "foo"
+	c := Events{
+		&TimerEvent{
+			metricName: name,
+			value:      300,
+		},
+	}
+	events <- c
+	ex := NewExporter(&metricMapper{}, true)
+	ex.mapper.Defaults.TimerType = timerTypeHistogram
+
+	// Close channel to signify we are done with the listener after a short period.
+	go func() {
+		time.Sleep(time.Millisecond * 100)
+		close(events)
+	}()
+	mock := &MockHistogram{}
+	key := hashNameAndLabels(name+"_timer", nil)
+	ex.Histograms.Elements[key] = mock
+	ex.Listen(events)
+	if mock.value == 300 {
+		t.Fatalf("Histogram observations not scaled into Seconds")
+	} else if mock.value != .300 {
+		t.Fatalf("Received unexpected value for histogram observation %f != .300", mock.value)
+	}
+}
+
 type statsDPacketHandler interface {
 	handlePacket(packet []byte, e chan<- Events)
 }