Support full-duplex http1.1

Signed-off-by: Jack Kleeman <jackkleeman@gmail.com>

Author: jackkleeman

CHANGELOG.md

@@ -32,6 +32,7 @@ This changelog keeps track of work items that have been completed and are ready
 ### Improvements
 
 - **General**: Make interceptor request logging optional ([#1375](https://github.com/kedacore/http-add-on/pull/1375))
+- **Interceptor**: Add support for full-duplex HTTP1.1 ([#1386](https://github.com/kedacore/http-add-on/pull/1386))
 
 ### Fixes
 

interceptor/middleware/responsewriter.go

@@ -58,3 +58,12 @@ func (rw *responseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 
 	return nil, nil, errors.New("http.Hijacker not implemented")
 }
+
+// https://pkg.go.dev/net/http#ResponseController.EnableFullDuplex
+func (rw *responseWriter) EnableFullDuplex() error {
+	if hj, ok := rw.downstreamResponseWriter.(interface{ EnableFullDuplex() error }); ok {
+		return hj.EnableFullDuplex()
+	}
+
+	return errors.New("EnableFullDuplex() not implemented")
+}

interceptor/proxy_handlers.go

@@ -109,6 +109,11 @@ func newForwardingHandler(
 		r.Header.Add("X-KEDA-HTTP-Cold-Start-Ref-Name", httpso.Spec.ScaleTargetRef.Name)
 		r.Header.Add("X-KEDA-HTTP-Cold-Start-Ref-Namespace", httpso.Namespace)
 
+		rc := http.NewResponseController(w)
+		if err := rc.EnableFullDuplex(); err != nil {
+			lggr.Error(err, "Could not enable full duplex on responsewriter, continuing")
+		}
+
 		shouldFailover := hasFailover && err != nil
 		if tracingCfg.Enabled {
 			uh = handler.NewUpstream(otelhttp.NewTransport(roundTripper), tracingCfg, shouldFailover)