Implement http.Hijacker for otelmux

CHANGELOG.md

@@ -9,7 +9,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ## [Unreleased]
 
 ### Added
-
+- Implement `http.Hijacker` in`go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux`. (#5796)
 - Add `NewProducer` to `go.opentelemetry.io/contrib/instrumentation/runtime`, which allows collecting the `go.schedule.duration` histogram metric from the Go runtime. (#5991)
 - Add gRPC protocol support for OTLP log exporter in `go.opentelemetry.io/contrib/exporters/autoexport`. (#6083)
 

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"
 
@@ -76,6 +78,13 @@ type recordingResponseWriter struct {
 	status  int
 }
 
+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")
+}
+
 var rrwPool = &sync.Pool{
 	New: func() interface{} {
 		return &recordingResponseWriter{}

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

@@ -23,6 +23,63 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
+func TestRecordingResponseWriterHijackWithMiddleware(t *testing.T) {
+	// Create a mock HTTP handler
+	mockHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		hj, ok := w.(http.Hijacker)
+		require.True(t, ok, "ResponseWriter does not implement http.Hijacker")
+
+		conn, rw, err := hj.Hijack()
+		require.NoError(t, err)
+		assert.NotNil(t, conn)
+		assert.NotNil(t, rw)
+
+		err = conn.Close()
+		require.NoError(t, err)
+	})
+
+	// Wrap the handler with otelmux.Middleware
+	router := mux.NewRouter()
+	router.Use(otelmux.Middleware("test-service"))
+	router.Handle("/hijack", mockHandler)
+
+	// Create a mock HTTP request and response writer
+	req := httptest.NewRequest("GET", "http://example.com/hijack", nil)
+	rr := httptest.NewRecorder()
+
+	// Serve the HTTP request using the wrapped handler
+	router.ServeHTTP(rr, req)
+
+	// Verify the response status
+	assert.Equal(t, http.StatusOK, rr.Code)
+}
+
+func TestRecordingResponseWriterHijackNonHijackerWithMiddleware(t *testing.T) {
+	// Create a mock HTTP handler
+	mockHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		hj, ok := w.(http.Hijacker)
+		require.False(t, ok, "ResponseWriter should not implement http.Hijacker")
+
+		_, _, err := hj.Hijack()
+		assert.Error(t, err)
+	})
+
+	// Wrap the handler with otelmux.Middleware
+	router := mux.NewRouter()
+	router.Use(otelmux.Middleware("test-service"))
+	router.Handle("/non-hijack", mockHandler)
+
+	// Create a mock HTTP request and response writer
+	req := httptest.NewRequest("GET", "http://example.com/non-hijack", nil)
+	rr := httptest.NewRecorder()
+
+	// Serve the HTTP request using the wrapped handler
+	router.ServeHTTP(rr, req)
+
+	// Verify the response status
+	assert.Equal(t, http.StatusOK, rr.Code)
+}
+
 func TestCustomSpanNameFormatter(t *testing.T) {
 	exporter := tracetest.NewInMemoryExporter()