Add route tag to metrics as well as traces when using WithRouteTag.

Resolves open-telemetry#611.

instrumentation/net/http/otelhttp/handler.go

@@ -249,8 +249,14 @@ func setAfterServeAttributes(span trace.Span, read, wrote int64, statusCode int,
 // RouteKey Tag.
 func WithRouteTag(route string, h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attr := semconv.HTTPRouteKey.String(route)
+
 		span := trace.SpanFromContext(r.Context())
-		span.SetAttributes(semconv.HTTPRouteKey.String(route))
+		span.SetAttributes(attr)
+
+		labeler, _ := LabelerFromContext(r.Context())
+		labeler.Add(attr)
+
 		h.ServeHTTP(w, r)
 	})
 }

instrumentation/net/http/otelhttp/test/go.mod

@@ -7,6 +7,7 @@ require (
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.36.4
 	go.opentelemetry.io/otel v1.11.1
 	go.opentelemetry.io/otel/sdk v1.11.1
+	go.opentelemetry.io/otel/sdk/metric v0.33.0
 	go.opentelemetry.io/otel/trace v1.11.1
 )
 

instrumentation/net/http/otelhttp/test/go.sum

@@ -24,6 +24,8 @@ go.opentelemetry.io/otel/metric v0.33.0 h1:xQAyl7uGEYvrLAiV/09iTJlp1pZnQ9Wl793qb
 go.opentelemetry.io/otel/metric v0.33.0/go.mod h1:QlTYc+EnYNq/M2mNk1qDDMRLpqCOj2f/r5c7Fd5FYaI=
 go.opentelemetry.io/otel/sdk v1.11.1 h1:F7KmQgoHljhUuJyA+9BiU+EkJfyX5nVVF4wyzWZpKxs=
 go.opentelemetry.io/otel/sdk v1.11.1/go.mod h1:/l3FE4SupHJ12TduVjUkZtlfFqDCQJlOlithYrdktys=
+go.opentelemetry.io/otel/sdk/metric v0.33.0 h1:oTqyWfksgKoJmbrs2q7O7ahkJzt+Ipekihf8vhpa9qo=
+go.opentelemetry.io/otel/sdk/metric v0.33.0/go.mod h1:xdypMeA21JBOvjjzDUtD0kzIcHO/SPez+a8HOzJPGp0=
 go.opentelemetry.io/otel/trace v1.11.1 h1:ofxdnzsNrGBYXbP7t7zpUK281+go5rF7dvdIZXF8gdQ=
 go.opentelemetry.io/otel/trace v1.11.1/go.mod h1:f/Q9G7vzk5u91PhbmKbg1Qn0rzH1LJ4vbPHFGkTPtOk=
 golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8 h1:h+EGohizhe9XlX18rfpa8k8RAc5XyaeamM+0VHRd4lc=

instrumentation/net/http/otelhttp/test/handler_test.go

@@ -26,13 +26,18 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+	semconv "go.opentelemetry.io/otel/semconv/v1.12.0"
+
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
 	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/metric"
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	"go.opentelemetry.io/otel/sdk/trace/tracetest"
 	"go.opentelemetry.io/otel/trace"
+
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 )
 
 // TODO(#2759): Add metric integration tests for the instrumentation. These
@@ -334,3 +339,55 @@ func TestSpanStatus(t *testing.T) {
 		})
 	}
 }
+
+func TestWithRouteTag(t *testing.T) {
+	route := "/some/route"
+
+	spanRecorder := tracetest.NewSpanRecorder()
+	tracerProvider := sdktrace.NewTracerProvider()
+	tracerProvider.RegisterSpanProcessor(spanRecorder)
+
+	metricReader := metric.NewManualReader()
+	meterProvider := metric.NewMeterProvider(metric.WithReader(metricReader))
+
+	h := otelhttp.NewHandler(
+		otelhttp.WithRouteTag(
+			route,
+			http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusTeapot)
+			}),
+		),
+		"test_handler",
+		otelhttp.WithTracerProvider(tracerProvider),
+		otelhttp.WithMeterProvider(meterProvider),
+	)
+
+	h.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "/", nil))
+	expectedAttribute := semconv.HTTPRouteKey.String(route)
+
+	require.Len(t, spanRecorder.Ended(), 1, "should emit a span")
+	span := spanRecorder.Ended()[0]
+	require.Contains(t, span.Attributes(), expectedAttribute, "should add route to span attributes")
+
+	collectedMetrics, err := metricReader.Collect(context.Background())
+	require.NoError(t, err)
+	require.Len(t, collectedMetrics.ScopeMetrics, 1, "should emit metrics for one scope")
+	scopeMetrics := collectedMetrics.ScopeMetrics[0]
+
+	for _, m := range scopeMetrics.Metrics {
+		switch m.Data.(type) {
+		case metricdata.Sum[int64]:
+			d := m.Data.(metricdata.Sum[int64])
+			require.Len(t, d.DataPoints, 1, "metric '%v' should have exactly one data point", m.Name)
+			require.Contains(t, d.DataPoints[0].Attributes.ToSlice(), expectedAttribute, "should add route to attributes for metric '%v'", m.Name)
+
+		case metricdata.Histogram:
+			d := m.Data.(metricdata.Histogram)
+			require.Len(t, d.DataPoints, 1, "metric '%v' should have exactly one data point", m.Name)
+			require.Contains(t, d.DataPoints[0].Attributes.ToSlice(), expectedAttribute, "should add route to attributes for metric '%v'", m.Name)
+
+		default:
+			require.Fail(t, "metric has unexpected data type", "metric '%v' has unexpected data type %T", m.Name, m.Data)
+		}
+	}
+}