Provide Log Body in OTEL access Log

pkg/middlewares/accesslog/logger.go

@@ -364,7 +364,10 @@ func (h *Handler) logTheRoundTrip(ctx context.Context, logDataTable *LogData) {
 	totalDuration := time.Now().UTC().Sub(core[StartUTC].(time.Time))
 	core[Duration] = totalDuration
 
-	if h.keepAccessLog(status, retryAttempts, totalDuration) {
+	if !h.keepAccessLog(status, retryAttempts, totalDuration) {
+		return
+	}
+
 	size := logDataTable.DownstreamResponse.size
 	core[DownstreamContentSize] = size
 	if original, ok := core[OriginContentSize]; ok {
@@ -393,10 +396,24 @@ func (h *Handler) logTheRoundTrip(ctx context.Context, logDataTable *LogData) {
 
 	h.mu.Lock()
 	defer h.mu.Unlock()
-		h.logger.WithContext(ctx).WithFields(fields).Println()
+
+	entry := h.logger.WithContext(ctx).WithFields(fields)
+
+	var message string
+	if h.config.OTLP != nil {
+		// If the logger is configured to use OpenTelemetry,
+		// we compute the log body with the formatter.
+		mBytes, err := h.logger.Formatter.Format(entry)
+		if err != nil {
+			message = fmt.Sprintf("Failed to format access log entry: %v", err)
+		} else {
+			message = string(mBytes)
 		}
 	}
 
+	entry.Println(message)
+}
+
 func (h *Handler) redactHeaders(headers http.Header, fields logrus.Fields, prefix string) {
 	for k := range headers {
 		v := h.config.Fields.KeepHeader(k)

pkg/middlewares/accesslog/logger_test.go

@@ -56,7 +56,38 @@ var (
 	testStart               = time.Now()
 )
 
-func TestOTelAccessLog(t *testing.T) {
+func TestOTelAccessLogWithBody(t *testing.T) {
+	testCases := []struct {
+		desc        string
+		format      string
+		bodyCheckFn func(*testing.T, string)
+	}{
+		{
+			desc:   "Common format with log body",
+			format: CommonFormat,
+			bodyCheckFn: func(t *testing.T, log string) {
+				t.Helper()
+
+				// For common format, verify the body contains the CLF formatted string
+				assert.Regexp(t, `"body":{"stringValue":".*- /health -.*200.*"}`, log)
+			},
+		},
+		{
+			desc:   "JSON format with log body",
+			format: JSONFormat,
+			bodyCheckFn: func(t *testing.T, log string) {
+				t.Helper()
+
+				// For JSON format, verify the body contains the JSON formatted string
+				assert.Regexp(t, `"body":{"stringValue":".*DownstreamStatus.*:200.*"}`, log)
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
 			logCh := make(chan string)
 			collector := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				gzr, err := gzip.NewReader(r.Body)
@@ -77,6 +108,7 @@ func TestOTelAccessLog(t *testing.T) {
 			t.Cleanup(collector.Close)
 
 			config := &types.AccessLog{
+				Format: test.format,
 				OTLP: &types.OTelLog{
 					ServiceName:        "test",
 					ResourceAttributes: map[string]string{"resource": "attribute"},
@@ -95,7 +127,7 @@ func TestOTelAccessLog(t *testing.T) {
 			req := &http.Request{
 				Header: map[string][]string{},
 				URL: &url.URL{
-			Path: testPath,
+					Path: "/health",
 				},
 			}
 			ctx := trace.ContextWithSpanContext(t.Context(), trace.NewSpanContext(trace.SpanContextConfig{
@@ -126,10 +158,19 @@ func TestOTelAccessLog(t *testing.T) {
 				t.Error("AccessLog not exported")
 
 			case log := <-logCh:
+				// Verify basic OTLP structure
 				assert.Regexp(t, `{"key":"resource","value":{"stringValue":"attribute"}}`, log)
 				assert.Regexp(t, `{"key":"service.name","value":{"stringValue":"test"}}`, log)
 				assert.Regexp(t, `{"key":"DownstreamStatus","value":{"intValue":"200"}}`, log)
 				assert.Regexp(t, `"traceId":"01020304050607080000000000000000","spanId":"0102030405060708"`, log)
+
+				// Most importantly, verify the log body is populated (not empty)
+				assert.NotRegexp(t, `"body":{"stringValue":""}`, log, "Log body should not be empty when OTLP is configured")
+
+				// Run format-specific body checks
+				test.bodyCheckFn(t, log)
+			}
+		})
 	}
 }