contrib/internal/httptrace: set http.host tag on request Host not URL…

….host (#1327)

contrib/internal/httptrace/httptrace.go

@@ -29,9 +29,9 @@ func StartRequestSpan(r *http.Request, opts ...ddtrace.StartSpanOption) (tracer.
 		tracer.Tag(ext.HTTPUserAgent, r.UserAgent()),
 		tracer.Measured(),
 	}, opts...)
-	if r.URL.Host != "" {
+	if r.Host != "" {
 		opts = append([]ddtrace.StartSpanOption{
-			tracer.Tag("http.host", r.URL.Host),
+			tracer.Tag("http.host", r.Host),
 		}, opts...)
 	}
 	if spanctx, err := tracer.Extract(tracer.HTTPHeadersCarrier(r.Header)); err == nil {

contrib/internal/httptrace/httptrace_test.go

@@ -0,0 +1,29 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016 Datadog, Inc.
+
+package httptrace
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/mocktracer"
+)
+
+func TestStartRequestSpan(t *testing.T) {
+	mt := mocktracer.Start()
+	defer mt.Stop()
+	r := httptest.NewRequest(http.MethodGet, "/somePath", nil)
+	s, _ := StartRequestSpan(r)
+	s.Finish()
+	spans := mt.FinishedSpans()
+
+	require.Len(t, spans, 1)
+	assert.Equal(t, "example.com", spans[0].Tag("http.host"))
+}