Implement http.Hijacker for otelmux

CHANGELOG.md

@@ -8,6 +8,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+- Implement `http.Hijacker` in`go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux`. (#6562)
+
 ### Added
 
 - Generate server metrics with semantic conventions v1.26 in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` when `OTEL_SEMCONV_STABILITY_OPT_IN` is set to `http/dup`. (#6411)

instrumentation/github.com/gorilla/mux/otelmux/mux.go

@@ -4,7 +4,9 @@
 package otelmux // import "go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux"
 
 import (
+	"bufio"
 	"fmt"
+	"net"
 	"net/http"
 	"sync"
 
@@ -108,6 +110,13 @@ func getRRW(writer http.ResponseWriter) *recordingResponseWriter {
 	return rrw
 }
 
+func (h *recordingResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if hijacker, ok := h.writer.(http.Hijacker); ok {
+		return hijacker.Hijack()
+	}
+	return nil, nil, fmt.Errorf("underlying ResponseWriter does not support hijacking")
+}
+
 func putRRW(rrw *recordingResponseWriter) {
 	rrw.writer = nil
 	rrwPool.Put(rrw)

instrumentation/github.com/gorilla/mux/otelmux/mux_test.go

@@ -35,17 +35,14 @@ func TestPassthroughSpanFromGlobalTracer(t *testing.T) {
 	// span context in the incoming request context.
 	router.HandleFunc("/user/{id}", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		called = true
-		got := trace.SpanFromContext(r.Context()).SpanContext()
-		assert.Equal(t, sc, got)
-		w.WriteHeader(http.StatusOK)
 	}))
 
-	r := httptest.NewRequest("GET", "/user/123", nil)
-	r = r.WithContext(trace.ContextWithRemoteSpanContext(context.Background(), sc))
+	req := httptest.NewRequest("GET", "/user/123", nil)
+	req = req.WithContext(trace.ContextWithSpanContext(context.Background(), sc))
 	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
 
-	router.ServeHTTP(w, r)
-	assert.True(t, called, "failed to run test")
+	assert.True(t, called)
 }
 
 func TestPropagationWithGlobalPropagators(t *testing.T) {
@@ -190,3 +187,18 @@ func TestFilter(t *testing.T) {
 	assert.Equal(t, 1, calledHealth, "failed to run test")
 	assert.Equal(t, 1, calledTest, "failed to run test")
 }
+
+func TestRecordingResponseWriterHijack(t *testing.T) {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rrw := getRRW(w)
+		conn, rw, err := rrw.Hijack()
+		assert.Nil(t, conn)
+		assert.Nil(t, rw)
+		assert.NotNil(t, err)
+		assert.Equal(t, "underlying ResponseWriter does not support hijacking", err.Error())
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+}

instrumentation/github.com/gorilla/mux/otelmux/test/mux_test.go

@@ -282,3 +282,25 @@ func TestWithPublicEndpointFn(t *testing.T) {
 		})
 	}
 }
+
+func getRRW(w http.ResponseWriter) http.Hijacker {
+	if hijacker, ok := w.(http.Hijacker); ok {
+		return hijacker
+	}
+	return nil
+}
+
+func TestRecordingResponseWriterHijack(t *testing.T) {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rrw := getRRW(w)
+		conn, rw, err := rrw.Hijack()
+		assert.Nil(t, conn)
+		assert.Nil(t, rw)
+		assert.NotNil(t, err)
+		assert.Equal(t, "underlying ResponseWriter does not support hijacking", err.Error())
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	handler.ServeHTTP(w, req)
+}