feat(otelgin): add the WithGinMetricAttributes option to allow setting dynamic, per-request metric attributes based on *gin.Context

CHANGELOG.md

@@ -15,6 +15,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `WithAttributes` option to set instrumentation scope attributes on the created `log.Logger` in `go.opentelemetry.io/contrib/bridges/otelslog`. (#6965)
 - Add `WithAttributes` option to set instrumentation scope attributes on the created `log.Logger` in `go.opentelemetry.io/contrib/bridges/otellogrus`. (#6966)
 - Add `WithAttributes` option to set instrumentation scope attributes on the created `log.Logger` in `go.opentelemetry.io/contrib/bridges/otellogr`. (#6967)
+- Add the `WithGinMetricAttributes` option to allow setting dynamic, per-request metric attributes based on `*gin.Context` in `go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin`. (#6932)
 
 ### Changed
 

instrumentation/github.com/gin-gonic/gin/otelgin/config.go

@@ -17,13 +17,14 @@ import (
 )
 
 type config struct {
-	TracerProvider    oteltrace.TracerProvider
-	Propagators       propagation.TextMapPropagator
-	Filters           []Filter
-	GinFilters        []GinFilter
-	SpanNameFormatter SpanNameFormatter
-	MeterProvider     metric.MeterProvider
-	MetricAttributeFn MetricAttributeFn
+	TracerProvider       oteltrace.TracerProvider
+	Propagators          propagation.TextMapPropagator
+	Filters              []Filter
+	GinFilters           []GinFilter
+	SpanNameFormatter    SpanNameFormatter
+	MeterProvider        metric.MeterProvider
+	MetricAttributeFn    MetricAttributeFn
+	GinMetricAttributeFn GinMetricAttributeFn
 }
 
 // Filter is a predicate used to determine whether a given http.request should
@@ -41,6 +42,10 @@ type SpanNameFormatter func(r *http.Request) string
 // and return them as a slice of attribute.KeyValue.
 type MetricAttributeFn func(*http.Request) []attribute.KeyValue
 
+// GinMetricAttributeFn is used to extract additional attributes from the gin.Context
+// and return them as a slice of attribute.KeyValue.
+type GinMetricAttributeFn func(*gin.Context) []attribute.KeyValue
+
 // Option specifies instrumentation configuration options.
 type Option interface {
 	apply(*config)
@@ -110,8 +115,20 @@ func WithMeterProvider(mp metric.MeterProvider) Option {
 
 // WithMetricAttributeFn specifies a function that extracts additional attributes from the http.Request
 // and returns them as a slice of attribute.KeyValue.
+//
+// If attributes are duplicated between this method and `WithGinMetricAttributeFn`, the attributes in this method will be overridden.
 func WithMetricAttributeFn(f MetricAttributeFn) Option {
 	return optionFunc(func(c *config) {
 		c.MetricAttributeFn = f
 	})
 }
+
+// WithGinMetricAttributeFn specifies a function that extracts additional attributes from the gin.Context
+// and returns them as a slice of attribute.KeyValue.
+//
+// If attributes are duplicated between this method and `WithMetricAttributeFn`, the attributes in this method will be used.
+func WithGinMetricAttributeFn(f GinMetricAttributeFn) Option {
+	return optionFunc(func(c *config) {
+		c.GinMetricAttributeFn = f
+	})
+}

instrumentation/github.com/gin-gonic/gin/otelgin/gin.go

@@ -118,7 +118,10 @@ func Middleware(service string, opts ...Option) gin.HandlerFunc {
 		// Record the server-side attributes.
 		var additionalAttributes []attribute.KeyValue
 		if cfg.MetricAttributeFn != nil {
-			additionalAttributes = cfg.MetricAttributeFn(c.Request)
+			additionalAttributes = append(additionalAttributes, cfg.MetricAttributeFn(c.Request)...)
+		}
+		if cfg.GinMetricAttributeFn != nil {
+			additionalAttributes = append(additionalAttributes, cfg.GinMetricAttributeFn(c)...)
 		}
 
 		sc.RecordMetrics(ctx, semconv.ServerMetricData{

instrumentation/github.com/gin-gonic/gin/otelgin/test/gin_test.go

@@ -439,17 +439,30 @@ func TestWithGinFilter(t *testing.T) {
 
 func TestMetrics(t *testing.T) {
 	tests := []struct {
-		name                     string
-		metricAttributeExtractor func(*http.Request) []attribute.KeyValue
+		name                        string
+		metricAttributeExtractor    func(*http.Request) []attribute.KeyValue
+		ginMetricAttributeExtractor func(*gin.Context) []attribute.KeyValue
 	}{
-		{"default", nil},
-		{"with metric attributes callback", func(req *http.Request) []attribute.KeyValue {
-			return []attribute.KeyValue{
-				attribute.String("key1", "value1"),
-				attribute.String("key2", "value"),
-				attribute.String("method", strings.ToUpper(req.Method)),
-			}
-		}},
+		{
+			name:                        "default",
+			metricAttributeExtractor:    nil,
+			ginMetricAttributeExtractor: nil,
+		},
+		{
+			name: "with metric attributes callback",
+			metricAttributeExtractor: func(r *http.Request) []attribute.KeyValue {
+				return []attribute.KeyValue{
+					attribute.String("key1", "value1"),
+					attribute.String("key2", "value"),
+					attribute.String("method", strings.ToUpper(r.Method)),
+				}
+			},
+			ginMetricAttributeExtractor: func(c *gin.Context) []attribute.KeyValue {
+				return []attribute.KeyValue{
+					attribute.String("key3", "value3"),
+				}
+			},
+		},
 	}
 
 	for _, tt := range tests {
@@ -461,6 +474,7 @@ func TestMetrics(t *testing.T) {
 			router.Use(otelgin.Middleware("foobar",
 				otelgin.WithMeterProvider(meterProvider),
 				otelgin.WithMetricAttributeFn(tt.metricAttributeExtractor),
+				otelgin.WithGinMetricAttributeFn(tt.ginMetricAttributeExtractor),
 			))
 			router.GET("/user/:id", func(c *gin.Context) {
 				id := c.Param("id")
@@ -470,6 +484,8 @@ func TestMetrics(t *testing.T) {
 
 			r := httptest.NewRequest("GET", "/user/123", nil)
 			w := httptest.NewRecorder()
+			c, _ := gin.CreateTestContext(w)
+			c.Request = r
 			router.ServeHTTP(w, r)
 
 			// verify metrics
@@ -493,6 +509,9 @@ func TestMetrics(t *testing.T) {
 			if tt.metricAttributeExtractor != nil {
 				attrs = append(attrs, tt.metricAttributeExtractor(r)...)
 			}
+			if tt.ginMetricAttributeExtractor != nil {
+				attrs = append(attrs, tt.ginMetricAttributeExtractor(c)...)
+			}
 
 			metricdatatest.AssertEqual(t, metricdata.Metrics{
 				Name:        "http.server.request.size",