fix: reject logs after response flush failure

proxy/writer.go

@@ -66,16 +66,21 @@ func (c *captureWriter) Write(p []byte) (int, error) {
 		if isStreamResponse(c.Header()) {
 			c.sse.Write(p[:n])
 		}
-		if f, ok := c.ResponseWriter.(http.Flusher); ok {
-			f.Flush()
-		}
+		c.flush()
 	}
 	return n, err
 }
 
 func (c *captureWriter) Flush() {
-	if f, ok := c.ResponseWriter.(http.Flusher); ok {
-		f.Flush()
+	c.flush()
+}
+
+func (c *captureWriter) flush() {
+	if _, ok := c.ResponseWriter.(http.Flusher); !ok {
+		return
+	}
+	if err := http.NewResponseController(c.ResponseWriter).Flush(); err != nil {
+		c.writeFailed = true
 	}
 }