support metrics sending via grpc

cmd/kuriweb/http.go

@@ -16,7 +16,8 @@ import (
 	"github.com/gorilla/mux"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
-	semconv "go.opentelemetry.io/otel/semconv/v1.25.0"
+	"go.opentelemetry.io/otel/metric"
+	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
 	"go.opentelemetry.io/otel/trace"
 )
 
@@ -57,6 +58,7 @@ func setupHTTP(cfg config.HTTP, srv xhttp.Server, log *slog.Logger) *http.Server
 		mux.CORSMethodMiddleware(router),
 		middlewareLogger(log),
 		middlewareTrace(),
+		middlewareMetrics(),
 	)
 
 	setupCoursesHTTP(srv, router, log)
@@ -114,6 +116,53 @@ func (k attributeStringKey) Value(value string) attribute.KeyValue {
 	return attribute.String(string(k), value)
 }
 
+func must[T any](value T, err error) T {
+	if err != nil {
+		panic(err.Error())
+	}
+
+	return value
+}
+
+func middlewareMetrics() mux.MiddlewareFunc {
+	requestDuration := must(webmetric.Float64Histogram(
+		semconv.HTTPServerRequestDurationName,
+		metric.WithUnit(semconv.HTTPServerRequestDurationUnit),
+		metric.WithDescription(semconv.HTTPServerRequestDurationDescription),
+	))
+
+	f := func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			start := time.Now()
+
+			route := mux.CurrentRoute(r)
+			hpath, _ := route.GetPathTemplate()
+
+			attributes := make([]attribute.KeyValue, 0, 8)
+			attributes = append(
+				attributes,
+				semconv.HTTPRequestMethodOriginal(r.Method),
+				semconv.URLFull(hpath),
+				semconv.URLPath(r.URL.Path),
+			)
+			next.ServeHTTP(w, r)
+
+			if wr, ok := w.(*customResponseWriter); ok {
+				statusCode := xdefault.WithFallback(wr.statusCode, http.StatusOK)
+				attributes = append(attributes,
+					semconv.HTTPResponseStatusCode(statusCode),
+					semconv.HTTPResponseBodySize(wr.wroteBytes),
+				)
+			}
+			elapsed := time.Since(start).Truncate(time.Millisecond)
+			requestDuration.Record(
+				r.Context(), elapsed.Seconds(), metric.WithAttributes(attributes...))
+		})
+	}
+
+	return f
+}
+
 func middlewareTrace() mux.MiddlewareFunc {
 	reqidAttr := attributeStringKey("http.request_id")