contrib/net/http: add errCheck function

contrib/net/http/option.go

@@ -129,6 +129,7 @@ type roundTripperConfig struct {
 	resourceNamer func(req *http.Request) string
 	ignoreRequest func(*http.Request) bool
 	spanOpts      []ddtrace.StartSpanOption
+	errCheck      func(err error) bool
 }
 
 func newRoundTripperConfig() *roundTripperConfig {
@@ -216,3 +217,12 @@ func RTWithIgnoreRequest(f func(*http.Request) bool) RoundTripperOption {
 		cfg.ignoreRequest = f
 	}
 }
+
+// RTWithErrorCheck specifies a function fn which determines whether the passed
+// error should be marked as an error. The fn is called whenever an aws operation
+// finishes with an error
+func RTWithErrorCheck(fn func(err error) bool) RoundTripperOption {
+	return func(cfg *roundTripperConfig) {
+		cfg.errCheck = fn
+	}
+}

contrib/net/http/roundtripper.go

@@ -52,7 +52,11 @@ func (rt *roundTripper) RoundTrip(req *http.Request) (res *http.Response, err er
 		if rt.cfg.after != nil {
 			rt.cfg.after(res, span)
 		}
-		span.Finish(tracer.WithError(err))
+		if rt.cfg.errCheck == nil || rt.cfg.errCheck(err) {
+			span.Finish(tracer.WithError(err))
+		} else {
+			span.Finish()
+		}
 	}()
 	if rt.cfg.before != nil {
 		rt.cfg.before(req, span)
@@ -67,7 +71,9 @@ func (rt *roundTripper) RoundTrip(req *http.Request) (res *http.Response, err er
 	res, err = rt.base.RoundTrip(r2)
 	if err != nil {
 		span.SetTag("http.errors", err.Error())
-		span.SetTag(ext.Error, err)
+		if rt.cfg.errCheck == nil || rt.cfg.errCheck(err) {
+			span.SetTag(ext.Error, err)
+		}
 	} else {
 		span.SetTag(ext.HTTPCode, strconv.Itoa(res.StatusCode))
 		// treat 5XX as errors

contrib/net/http/roundtripper_test.go

@@ -183,6 +183,53 @@ func TestRoundTripperNetworkError(t *testing.T) {
 	assert.Equal(t, "net/http", s0.Tag(ext.Component))
 }
 
+func TestRoundTripperNetworkErrorWithErrorCheck(t *testing.T) {
+	failedRequest := func(t *testing.T, mt mocktracer.Tracer, forwardErr bool, opts ...RoundTripperOption) mocktracer.Span {
+		done := make(chan struct{})
+		s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			_, err := tracer.Extract(tracer.HTTPHeadersCarrier(r.Header))
+			assert.NoError(t, err)
+			<-done
+		}))
+		defer s.Close()
+		defer close(done)
+
+		rt := WrapRoundTripper(http.DefaultTransport,
+			RTWithErrorCheck(func(err error) bool {
+				return forwardErr
+			}))
+
+		client := &http.Client{
+			Transport: rt,
+			Timeout:   1 * time.Millisecond,
+		}
+
+		client.Get(s.URL + "/hello/world")
+
+		spans := mt.FinishedSpans()
+		assert.Len(t, spans, 1)
+
+		s0 := spans[0]
+		return s0
+	}
+
+	t.Run("error skipped", func(t *testing.T) {
+		mt := mocktracer.Start()
+		defer mt.Stop()
+
+		span := failedRequest(t, mt, false)
+		assert.Nil(t, span.Tag(ext.Error))
+	})
+
+	t.Run("error forwarded", func(t *testing.T) {
+		mt := mocktracer.Start()
+		defer mt.Stop()
+
+		span := failedRequest(t, mt, true)
+		assert.NotNil(t, span.Tag(ext.Error))
+	})
+}
+
 func TestRoundTripperCredentials(t *testing.T) {
 	mt := mocktracer.Start()
 	defer mt.Stop()