otelhttptrace: get tracerprovider from context if available (#874)

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

Co-authored-by: Aaron Clawson <Aaron.Clawson@gmail.com>

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Changed
 
+- `otelhttptrace.NewClientTrace` now uses `TracerProvider` from the parent context if one exists and none was set with `WithTracerProvider` (#874)
 - Changed the project minimum supported Go version from 1.15 to 1.16. (#1442)
 
 ### Fixed

instrumentation/net/http/httptrace/otelhttptrace/clienttrace.go

@@ -146,9 +146,8 @@ type clientTracer struct {
 // Proxy-Authorization, Cookie, and Set-Cookie.
 func NewClientTrace(ctx context.Context, opts ...ClientTraceOption) *httptrace.ClientTrace {
 	ct := &clientTracer{
-		Context:        ctx,
-		tracerProvider: otel.GetTracerProvider(),
-		activeHooks:    make(map[string]context.Context),
+		Context:     ctx,
+		activeHooks: make(map[string]context.Context),
 		redactedHeaders: map[string]struct{}{
 			"authorization":       {},
 			"www-authenticate":    {},
@@ -160,6 +159,13 @@ func NewClientTrace(ctx context.Context, opts ...ClientTraceOption) *httptrace.C
 		addHeaders: true,
 		useSpans:   true,
 	}
+
+	if span := trace.SpanFromContext(ctx); span.SpanContext().IsValid() {
+		ct.tracerProvider = span.TracerProvider()
+	} else {
+		ct.tracerProvider = otel.GetTracerProvider()
+	}
+
 	for _, opt := range opts {
 		opt.apply(ct)
 	}

instrumentation/net/http/httptrace/otelhttptrace/test/clienttrace_test.go

@@ -471,3 +471,36 @@ func TestWithInsecureHeaders(t *testing.T) {
 		gotAttributes,
 	)
 }
+
+func TestHTTPRequestWithTraceContext(t *testing.T) {
+	sr := tracetest.NewSpanRecorder()
+	tp := trace.NewTracerProvider(trace.WithSpanProcessor(sr))
+
+	// Mock http server
+	ts := httptest.NewServer(
+		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		}),
+	)
+	defer ts.Close()
+
+	ctx, span := tp.Tracer("").Start(context.Background(), "parent_span")
+
+	req, _ := http.NewRequest("GET", ts.URL, nil)
+	req = req.WithContext(httptrace.WithClientTrace(req.Context(), otelhttptrace.NewClientTrace(ctx)))
+
+	client := ts.Client()
+	res, err := client.Do(req)
+	require.NoError(t, err)
+	_ = res.Body.Close()
+
+	span.End()
+
+	parent, ok := getSpanFromRecorder(sr, "parent_span")
+	require.True(t, ok)
+
+	getconn, ok := getSpanFromRecorder(sr, "http.getconn")
+	require.True(t, ok)
+
+	require.Equal(t, parent.SpanContext().TraceID(), getconn.SpanContext().TraceID())
+	require.Equal(t, parent.SpanContext().SpanID(), getconn.Parent().SpanID())
+}