otelfiber: add WithCustomMetricAttrbutes option

otelfiber/config.go

@@ -10,15 +10,16 @@ import (
 
 // config is used to configure the Fiber middleware.
 type config struct {
-	Next              func(*fiber.Ctx) bool
-	TracerProvider    oteltrace.TracerProvider
-	MeterProvider     otelmetric.MeterProvider
-	Port              *int
-	Propagators       propagation.TextMapPropagator
-	ServerName        *string
-	SpanNameFormatter func(*fiber.Ctx) string
-	CustomAttributes  func(*fiber.Ctx) []attribute.KeyValue
-	collectClientIP   bool
+	Next                   func(*fiber.Ctx) bool
+	TracerProvider         oteltrace.TracerProvider
+	MeterProvider          otelmetric.MeterProvider
+	Port                   *int
+	Propagators            propagation.TextMapPropagator
+	ServerName             *string
+	SpanNameFormatter      func(*fiber.Ctx) string
+	CustomAttributes       func(*fiber.Ctx) []attribute.KeyValue
+	CustomMetricAttributes func(*fiber.Ctx) []attribute.KeyValue
+	collectClientIP        bool
 }
 
 // Option specifies instrumentation configuration options.
@@ -98,6 +99,14 @@ func WithCustomAttributes(f func(ctx *fiber.Ctx) []attribute.KeyValue) Option {
 	})
 }
 
+// WithCustomMetricAttributes specifies a function that will be called on every
+// request and the returned attributes will be added to the metrics.
+func WithCustomMetricAttributes(f func(ctx *fiber.Ctx) []attribute.KeyValue) Option {
+	return optionFunc(func(cfg *config) {
+		cfg.CustomMetricAttributes = f
+	})
+}
+
 // WithCollectClientIP specifies whether to collect the client's IP address
 // from the request. This is enabled by default.
 func WithCollectClientIP(collect bool) Option {

otelfiber/fiber.go

@@ -132,13 +132,13 @@ func Middleware(opts ...Option) fiber.Handler {
 			semconv.HTTPAttributesFromHTTPStatusCode(c.Response().StatusCode()),
 			semconv.HTTPRouteKey.String(c.Route().Path), // no need to copy c.Route().Path: route strings should be immutable across app lifecycle
 		)
-		
+
 		var responseSize int64
 		requestSize := int64(len(c.Request().Body()))
 		if c.GetRespHeader("Content-Type") != "text/event-stream" {
 			responseSize = int64(len(c.Response().Body()))
 		}
-		
+
 		defer func() {
 			responseMetricAttrs = append(
 				responseMetricAttrs,

otelfiber/otelfiber_test/fiber_test.go

@@ -447,6 +447,60 @@ func TestCustomAttributes(t *testing.T) {
 	assert.Contains(t, attr, attribute.String("http.query_params", "foo=bar"))
 }
 
+func TestCustomMetricAttributes(t *testing.T) {
+	reader := metric.NewManualReader()
+	provider := metric.NewMeterProvider(metric.WithReader(reader))
+
+	serverName := "foobar"
+	port := 8080
+	route := "/foo"
+
+	app := fiber.New()
+	app.Use(
+		otelfiber.Middleware(
+			otelfiber.WithMeterProvider(provider),
+			otelfiber.WithPort(port),
+			otelfiber.WithServerName(serverName),
+			otelfiber.WithCustomMetricAttributes(func(ctx *fiber.Ctx) []attribute.KeyValue {
+				return []attribute.KeyValue{
+					attribute.Key("http.query_params").String(ctx.Request().URI().QueryArgs().String()),
+				}
+			}),
+		),
+	)
+
+	app.Get(route, func(ctx *fiber.Ctx) error {
+		return ctx.SendStatus(http.StatusOK)
+	})
+
+	r := httptest.NewRequest(http.MethodGet, "/foo?foo=bar", nil)
+	resp, _ := app.Test(r)
+
+	// do and verify the request
+	require.Equal(t, http.StatusOK, resp.StatusCode)
+
+	metrics := metricdata.ResourceMetrics{}
+	err := reader.Collect(context.Background(), &metrics)
+	assert.NoError(t, err)
+	assert.Len(t, metrics.ScopeMetrics, 1)
+
+	requestAttrs := []attribute.KeyValue{
+		semconv.HTTPFlavorKey.String(fmt.Sprintf("1.%d", r.ProtoMinor)),
+		semconv.HTTPMethodKey.String(http.MethodGet),
+		semconv.HTTPSchemeHTTP,
+		semconv.NetHostNameKey.String(r.Host),
+		semconv.NetHostPortKey.Int(port),
+		semconv.HTTPServerNameKey.String(serverName),
+		attribute.String("http.query_params", "foo=bar"),
+	}
+	responseAttrs := append(
+		semconv.HTTPAttributesFromHTTPStatusCode(200),
+		semconv.HTTPRouteKey.String(route),
+	)
+
+	assertScopeMetrics(t, metrics.ScopeMetrics[0], route, requestAttrs, append(requestAttrs, responseAttrs...))
+}
+
 func TestOutboundTracingPropagation(t *testing.T) {
 	sr := new(tracetest.SpanRecorder)
 	provider := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr))

otelfiber/semconv.go

@@ -26,6 +26,10 @@ func httpServerMetricAttributesFromRequest(c *fiber.Ctx, cfg config) []attribute
 		attrs = append(attrs, semconv.HTTPServerNameKey.String(*cfg.ServerName))
 	}
 
+	if cfg.CustomMetricAttributes != nil {
+		attrs = append(attrs, cfg.CustomMetricAttributes(c)...)
+	}
+
 	return attrs
 }