[KFS-2199] extended the webserver to be dynamic so endpoint can be added and removed at runtime

Author: luca-filipponi

instrumentation/net/http/otelhttp/config.go

@@ -36,8 +36,9 @@ type config struct {
 	ClientTrace       func(context.Context) *httptrace.ClientTrace
 	Attributes        []attribute.KeyValue
 
-	TracerProvider trace.TracerProvider
-	MeterProvider  metric.MeterProvider
+	TracerProvider      trace.TracerProvider
+	MeterProvider       metric.MeterProvider
+	ReqAttributesMapper func(*http.Request) []attribute.KeyValue
 }
 
 // Option interface used for setting optional config properties.
@@ -198,9 +199,10 @@ func WithServerName(server string) Option {
 	})
 }
 
-// WithAttributes returns an option that sets of attributes to be always included in metrics.
-func WithAttributes(attributes []attribute.KeyValue) Option {
+// WithReqAttributesMapper returns an Option to set a function that maps an HTTP request to a slice of attribute.KeyValue.
+// These attributes will be included in metrics for every request.
+func WithReqAttributesMapper(reqAttributesMapper func(r *http.Request) []attribute.KeyValue) Option {
 	return optionFunc(func(c *config) {
-		c.Attributes = attributes
+		c.ReqAttributesMapper = reqAttributesMapper
 	})
 }

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

@@ -565,7 +565,9 @@ func TestDefaultAttributesHandling(t *testing.T) {
 
 	transport := otelhttp.NewTransport(
 		http.DefaultTransport, otelhttp.WithMeterProvider(provider),
-		otelhttp.WithAttributes(defaultAttributes))
+		otelhttp.WithReqAttributesMapper(func(_ *http.Request) []attribute.KeyValue {
+			return defaultAttributes
+		}))
 	client := http.Client{Transport: transport}
 
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {

instrumentation/net/http/otelhttp/transport.go

@@ -27,14 +27,14 @@ import (
 type Transport struct {
 	rt http.RoundTripper
 
-	tracer            trace.Tracer
-	meter             metric.Meter
-	propagators       propagation.TextMapPropagator
-	spanStartOptions  []trace.SpanStartOption
-	filters           []Filter
-	spanNameFormatter func(string, *http.Request) string
-	clientTrace       func(context.Context) *httptrace.ClientTrace
-	attributes        []attribute.KeyValue
+	tracer              trace.Tracer
+	meter               metric.Meter
+	propagators         propagation.TextMapPropagator
+	spanStartOptions    []trace.SpanStartOption
+	filters             []Filter
+	spanNameFormatter   func(string, *http.Request) string
+	clientTrace         func(context.Context) *httptrace.ClientTrace
+	reqAttributesMapper func(*http.Request) []attribute.KeyValue
 
 	semconv              semconv.HTTPClient
 	requestBytesCounter  metric.Int64Counter
@@ -80,7 +80,7 @@ func (t *Transport) applyConfig(c *config) {
 	t.filters = c.Filters
 	t.spanNameFormatter = c.SpanNameFormatter
 	t.clientTrace = c.ClientTrace
-	t.attributes = c.Attributes
+	t.reqAttributesMapper = c.ReqAttributesMapper
 }
 
 func (t *Transport) createMeasures() {
@@ -172,7 +172,7 @@ func (t *Transport) RoundTrip(r *http.Request) (*http.Response, error) {
 	}
 
 	// metrics
-	metricAttrs := append(append(labeler.Get(), semconvutil.HTTPClientRequestMetrics(r)...), t.attributes...)
+	metricAttrs := append(append(labeler.Get(), semconvutil.HTTPClientRequestMetrics(r)...), t.attributesFromRequest(r)...)
 	if res.StatusCode > 0 {
 		metricAttrs = append(metricAttrs, semconv.HTTPStatusCode(res.StatusCode))
 	}
@@ -198,6 +198,14 @@ func (t *Transport) RoundTrip(r *http.Request) (*http.Response, error) {
 	return res, err
 }
 
+func (t *Transport) attributesFromRequest(r *http.Request) []attribute.KeyValue {
+	var attributeForRequest []attribute.KeyValue
+	if t.reqAttributesMapper != nil {
+		attributeForRequest = t.reqAttributesMapper(r)
+	}
+	return attributeForRequest
+}
+
 // newWrappedBody returns a new and appropriately scoped *wrappedBody as an
 // io.ReadCloser. If the passed body implements io.Writer, the returned value
 // will implement io.ReadWriteCloser.