feat(logging): add upstream API request/response capture to streaming logs

internal/api/middleware/response_writer.go

@@ -232,7 +232,16 @@ func (w *ResponseWriterWrapper) Finalize(c *gin.Context) error {
 			w.streamDone = nil
 		}
 
+		// Write API Request and Response to the streaming log before closing
 		if w.streamWriter != nil {
+			apiRequest := w.extractAPIRequest(c)
+			if len(apiRequest) > 0 {
+				_ = w.streamWriter.WriteAPIRequest(apiRequest)
+			}
+			apiResponse := w.extractAPIResponse(c)
+			if len(apiResponse) > 0 {
+				_ = w.streamWriter.WriteAPIResponse(apiResponse)
+			}
 			if err := w.streamWriter.Close(); err != nil {
 				w.streamWriter = nil
 				return err

internal/logging/request_logger.go

@@ -84,6 +84,26 @@ type StreamingLogWriter interface {
 	//   - error: An error if writing fails, nil otherwise
 	WriteStatus(status int, headers map[string][]string) error
 
+	// WriteAPIRequest writes the upstream API request details to the log.
+	// This should be called before WriteStatus to maintain proper log ordering.
+	//
+	// Parameters:
+	//   - apiRequest: The API request data (typically includes URL, headers, body sent upstream)
+	//
+	// Returns:
+	//   - error: An error if writing fails, nil otherwise
+	WriteAPIRequest(apiRequest []byte) error
+
+	// WriteAPIResponse writes the upstream API response details to the log.
+	// This should be called after the streaming response is complete.
+	//
+	// Parameters:
+	//   - apiResponse: The API response data
+	//
+	// Returns:
+	//   - error: An error if writing fails, nil otherwise
+	WriteAPIResponse(apiResponse []byte) error
+
 	// Close finalizes the log file and cleans up resources.
 	//
 	// Returns:
@@ -252,6 +272,7 @@ func (l *FileRequestLogger) LogStreamingRequest(url, method string, headers map[
 		chunkChan:      make(chan []byte, 100), // Buffered channel for async writes
 		closeChan:      make(chan struct{}),
 		errorChan:      make(chan error, 1),
+		bufferedChunks: &bytes.Buffer{},
 	}
 
 	// Start async writer goroutine
@@ -628,11 +649,12 @@ func (l *FileRequestLogger) formatRequestInfo(url, method string, headers map[st
 
 // FileStreamingLogWriter implements StreamingLogWriter for file-based streaming logs.
 // It handles asynchronous writing of streaming response chunks to a file.
+// All data is buffered and written in the correct order when Close is called.
 type FileStreamingLogWriter struct {
 	// file is the file where log data is written.
 	file *os.File
 
-	// chunkChan is a channel for receiving response chunks to write.
+	// chunkChan is a channel for receiving response chunks to buffer.
 	chunkChan chan []byte
 
 	// closeChan is a channel for signaling when the writer is closed.
@@ -641,8 +663,23 @@ type FileStreamingLogWriter struct {
 	// errorChan is a channel for reporting errors during writing.
 	errorChan chan error
 
-	// statusWritten indicates whether the response status has been written.
+	// bufferedChunks stores the response chunks in order.
+	bufferedChunks *bytes.Buffer
+
+	// responseStatus stores the HTTP status code.
+	responseStatus int
+
+	// statusWritten indicates whether a non-zero status was recorded.
 	statusWritten bool
+
+	// responseHeaders stores the response headers.
+	responseHeaders map[string][]string
+
+	// apiRequest stores the upstream API request data.
+	apiRequest []byte
+
+	// apiResponse stores the upstream API response data.
+	apiResponse []byte
 }
 
 // WriteChunkAsync writes a response chunk asynchronously (non-blocking).
@@ -666,39 +703,65 @@ func (w *FileStreamingLogWriter) WriteChunkAsync(chunk []byte) {
 	}
 }
 
-// WriteStatus writes the response status and headers to the log.
+// WriteStatus buffers the response status and headers for later writing.
 //
 // Parameters:
 //   - status: The response status code
 //   - headers: The response headers
 //
 // Returns:
-//   - error: An error if writing fails, nil otherwise
+//   - error: Always returns nil (buffering cannot fail)
 func (w *FileStreamingLogWriter) WriteStatus(status int, headers map[string][]string) error {
-	if w.file == nil || w.statusWritten {
+	if status == 0 {
 		return nil
 	}
 
-	var content strings.Builder
+	w.responseStatus = status
-	content.WriteString("========================================\n")
+	if headers != nil {
-	content.WriteString("=== RESPONSE ===\n")
+		w.responseHeaders = make(map[string][]string, len(headers))
-	content.WriteString(fmt.Sprintf("Status: %d\n", status))
-
 		for key, values := range headers {
-		for _, value := range values {
+			headerValues := make([]string, len(values))
-			content.WriteString(fmt.Sprintf("%s: %s\n", key, value))
+			copy(headerValues, values)
+			w.responseHeaders[key] = headerValues
 		}
 	}
-	content.WriteString("\n")
-
-	_, err := w.file.WriteString(content.String())
-	if err == nil {
 	w.statusWritten = true
+	return nil
+}
+
+// WriteAPIRequest buffers the upstream API request details for later writing.
+//
+// Parameters:
+//   - apiRequest: The API request data (typically includes URL, headers, body sent upstream)
+//
+// Returns:
+//   - error: Always returns nil (buffering cannot fail)
+func (w *FileStreamingLogWriter) WriteAPIRequest(apiRequest []byte) error {
+	if len(apiRequest) == 0 {
+		return nil
 	}
-	return err
+	w.apiRequest = bytes.Clone(apiRequest)
+	return nil
+}
+
+// WriteAPIResponse buffers the upstream API response details for later writing.
+//
+// Parameters:
+//   - apiResponse: The API response data
+//
+// Returns:
+//   - error: Always returns nil (buffering cannot fail)
+func (w *FileStreamingLogWriter) WriteAPIResponse(apiResponse []byte) error {
+	if len(apiResponse) == 0 {
+		return nil
+	}
+	w.apiResponse = bytes.Clone(apiResponse)
+	return nil
 }
 
 // Close finalizes the log file and cleans up resources.
+// It writes all buffered data to the file in the correct order:
+// API REQUEST -> API RESPONSE -> RESPONSE (status, headers, body chunks)
 //
 // Returns:
 //   - error: An error if closing fails, nil otherwise
@@ -707,27 +770,85 @@ func (w *FileStreamingLogWriter) Close() error {
 		close(w.chunkChan)
 	}
 
-	// Wait for async writer to finish
+	// Wait for async writer to finish buffering chunks
 	if w.closeChan != nil {
 		<-w.closeChan
 		w.chunkChan = nil
 	}
 
-	if w.file != nil {
+	if w.file == nil {
-		return w.file.Close()
+		return nil
 	}
 
-	return nil
+	// Write all content in the correct order
+	var content strings.Builder
+
+	// 1. Write API REQUEST section
+	if len(w.apiRequest) > 0 {
+		if bytes.HasPrefix(w.apiRequest, []byte("=== API REQUEST")) {
+			content.Write(w.apiRequest)
+			if !bytes.HasSuffix(w.apiRequest, []byte("\n")) {
+				content.WriteString("\n")
+			}
+		} else {
+			content.WriteString("=== API REQUEST ===\n")
+			content.Write(w.apiRequest)
+			content.WriteString("\n")
+		}
+		content.WriteString("\n")
+	}
+
+	// 2. Write API RESPONSE section
+	if len(w.apiResponse) > 0 {
+		if bytes.HasPrefix(w.apiResponse, []byte("=== API RESPONSE")) {
+			content.Write(w.apiResponse)
+			if !bytes.HasSuffix(w.apiResponse, []byte("\n")) {
+				content.WriteString("\n")
+			}
+		} else {
+			content.WriteString("=== API RESPONSE ===\n")
+			content.Write(w.apiResponse)
+			content.WriteString("\n")
+		}
+		content.WriteString("\n")
+	}
+
+	// 3. Write RESPONSE section (status, headers, buffered chunks)
+	content.WriteString("========================================\n")
+	content.WriteString("=== RESPONSE ===\n")
+	if w.statusWritten {
+		content.WriteString(fmt.Sprintf("Status: %d\n", w.responseStatus))
+	}
+
+	for key, values := range w.responseHeaders {
+		for _, value := range values {
+			content.WriteString(fmt.Sprintf("%s: %s\n", key, value))
+		}
+	}
+	content.WriteString("\n")
+
+	// Write buffered response body chunks
+	if w.bufferedChunks != nil && w.bufferedChunks.Len() > 0 {
+		content.Write(w.bufferedChunks.Bytes())
+	}
+
+	// Write the complete content to file
+	if _, err := w.file.WriteString(content.String()); err != nil {
+		_ = w.file.Close()
+		return err
+	}
+
+	return w.file.Close()
 }
 
-// asyncWriter runs in a goroutine to handle async chunk writing.
+// asyncWriter runs in a goroutine to buffer chunks from the channel.
-// It continuously reads chunks from the channel and writes them to the file.
+// It continuously reads chunks from the channel and buffers them for later writing.
 func (w *FileStreamingLogWriter) asyncWriter() {
 	defer close(w.closeChan)
 
 	for chunk := range w.chunkChan {
-		if w.file != nil {
+		if w.bufferedChunks != nil {
-			_, _ = w.file.Write(chunk)
+			w.bufferedChunks.Write(chunk)
 		}
 	}
 }
@@ -754,6 +875,28 @@ func (w *NoOpStreamingLogWriter) WriteStatus(_ int, _ map[string][]string) error
 	return nil
 }
 
+// WriteAPIRequest is a no-op implementation that does nothing and always returns nil.
+//
+// Parameters:
+//   - apiRequest: The API request data (ignored)
+//
+// Returns:
+//   - error: Always returns nil
+func (w *NoOpStreamingLogWriter) WriteAPIRequest(_ []byte) error {
+	return nil
+}
+
+// WriteAPIResponse is a no-op implementation that does nothing and always returns nil.
+//
+// Parameters:
+//   - apiResponse: The API response data (ignored)
+//
+// Returns:
+//   - error: Always returns nil
+func (w *NoOpStreamingLogWriter) WriteAPIResponse(_ []byte) error {
+	return nil
+}
+
 // Close is a no-op implementation that does nothing and always returns nil.
 //
 // Returns: