otelgin: Using c.FullPath() to set http.route attribute (#5734)

As `spanName` can be customized with `SpanNameFormatter`, so the
`spanName` may not be the same with `http.route`, e.g. the `spanName`
can be `GET /users/:id`, but the `http.route` is `/users/:id`.
This PR using
[`c.FullPath()`](https://github.com/gin-gonic/gin/blob/v1.10.0/context.go#L165-L173)
to set `http.route` attribute in `otelgin` to keep `http.route` not
affected by `SpanNameFormatter`.

---------

Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>

CHANGELOG.md

@@ -17,6 +17,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - The superfluous `response.WriteHeader` call in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` when the response writer is flushed. (#5634)
 - Custom attributes targeting metrics recorded by the `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` are not ignored anymore. (#5129)
+- Use `c.FullPath()` method to set `http.route` attribute in `go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin`. (#5734)
 
 ### Deprecated
 

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

@@ -60,6 +60,7 @@ func Middleware(service string, opts ...Option) gin.HandlerFunc {
 		ctx := cfg.Propagators.Extract(savedCtx, propagation.HeaderCarrier(c.Request.Header))
 		opts := []oteltrace.SpanStartOption{
 			oteltrace.WithAttributes(semconvutil.HTTPServerRequest(service, c.Request)...),
+			oteltrace.WithAttributes(semconv.HTTPRoute(c.FullPath())),
 			oteltrace.WithSpanKind(oteltrace.SpanKindServer),
 		}
 		var spanName string
@@ -70,9 +71,6 @@ func Middleware(service string, opts ...Option) gin.HandlerFunc {
 		}
 		if spanName == "" {
 			spanName = fmt.Sprintf("HTTP %s route not found", c.Request.Method)
-		} else {
-			rAttr := semconv.HTTPRoute(spanName)
-			opts = append(opts, oteltrace.WithAttributes(rAttr))
 		}
 		ctx, span := tracer.Start(ctx, spanName, opts...)
 		defer span.End()

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

@@ -179,6 +179,42 @@ func TestSpanName(t *testing.T) {
 	}
 }
 
+func TestHTTPRouteWithSpanNameFormatter(t *testing.T) {
+	sr := tracetest.NewSpanRecorder()
+	provider := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr))
+
+	router := gin.New()
+	router.Use(otelgin.Middleware("foobar",
+		otelgin.WithTracerProvider(provider),
+		otelgin.WithSpanNameFormatter(func(r *http.Request) string {
+			return r.URL.Path
+		}),
+	),
+	)
+	router.GET("/user/:id", func(c *gin.Context) {
+		id := c.Param("id")
+		_, _ = c.Writer.Write([]byte(id))
+	})
+
+	r := httptest.NewRequest("GET", "/user/123", nil)
+	w := httptest.NewRecorder()
+
+	// do and verify the request
+	router.ServeHTTP(w, r)
+	response := w.Result()
+	require.Equal(t, http.StatusOK, response.StatusCode)
+
+	// verify traces look good
+	spans := sr.Ended()
+	require.Len(t, spans, 1)
+	span := spans[0]
+	assert.Equal(t, "/user/123", span.Name())
+	assert.Equal(t, oteltrace.SpanKindServer, span.SpanKind())
+	attr := span.Attributes()
+	assert.Contains(t, attr, attribute.String("http.method", "GET"))
+	assert.Contains(t, attr, attribute.String("http.route", "/user/:id"))
+}
+
 func TestHTML(t *testing.T) {
 	sr := tracetest.NewSpanRecorder()
 	provider := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr))