Add http status code to attributes and metrics

Taken from:

open-telemetry/opentelemetry-go-contrib#771

handler.go

@@ -105,8 +105,12 @@ func (h *Handler) createMeasures() {
 	serverLatencyMeasure, err := h.meter.NewInt64Histogram(ServerLatency)
 	handleErr(err)
 
+	requestCount, err := h.meter.NewInt64Counter(RequestCount)
+	handleErr(err)
+
 	h.counters[RequestContentLength] = requestBytesCounter
 	h.counters[ResponseContentLength] = responseBytesCounter
+	h.counters[RequestCount] = requestCount
 	h.valueRecorders[ServerLatency] = serverLatencyMeasure
 }
 
@@ -195,6 +199,10 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	h.counters[RequestContentLength].Add(ctx, bw.read, attributes...)
 	h.counters[ResponseContentLength].Add(ctx, rww.written, attributes...)
 
+	// Count of request to record errors ratio
+	requestCountAttributes := append(attributes, semconv.HTTPStatusCodeKey.Int(rww.statusCode))
+	h.counters[RequestCount].Add(ctx, 1, requestCountAttributes...)
+
 	elapsedTime := time.Since(requestStartTime).Microseconds()
 
 	h.valueRecorders[ServerLatency].Record(ctx, elapsedTime, attributes...)

test/handler_test.go

@@ -85,7 +85,20 @@ func TestHandlerBasics(t *testing.T) {
 		attribute.String("test", "attribute"),
 	}
 
-	assertMetricAttributes(t, attributesToVerify, meterProvider.MeasurementBatches)
+	var statusCodeBatch metrictest.Batch
+	var measurementBatches []metrictest.Batch
+	for _, batch := range meterProvider.MeasurementBatches {
+		batchName := batch.Measurements[0].Instrument.Descriptor().Name()
+		// separate the status code batch from the rest
+		if batchName == otelhttp.RequestCount {
+			statusCodeBatch = batch
+		} else {
+			measurementBatches = append(measurementBatches, batch)
+		}
+	}
+
+	assertMetricAttributes(t, attributesToVerify, measurementBatches)
+	assert.ElementsMatch(t, append(attributesToVerify, semconv.HTTPStatusCodeKey.Int(200)), statusCodeBatch.Labels)
 
 	if got, expected := rr.Result().StatusCode, http.StatusOK; got != expected {
 		t.Fatalf("got %d, expected %d", got, expected)