snapshot of https://github.com/centrifugal/centrifugo.git (master, 2026-09-16; blobs > 131072B omitted)

internal/middleware/http_instrumentation.go

@@ -0,0 +1,30 @@
+package middleware
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/centrifugal/centrifugo/v6/internal/metrics"
+)
+
+// HTTPServerInstrumentation is a middleware to instrument HTTP handlers.
+// Since it adds and extra layer of response wrapping Centrifugo doesn't use it by default.
+// Note, we can not simply collect durations here because we have handlers with long-lived
+// connections which require special care. So for now we just count requests.
+func HTTPServerInstrumentation(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rw := &statusResponseWriter{w, http.StatusOK}
+		next.ServeHTTP(rw, r)
+		status := strconv.Itoa(rw.status)
+		// Use the matched route pattern, not the raw request path. Subtree
+		// handlers (admin, swagger, dev, debug) accept arbitrary client-controlled
+		// sub-paths, so labeling by r.URL.Path would grow the Prometheus series map
+		// without bound (memory DoS). r.Pattern is the registered pattern that
+		// matched (e.g. "/admin/"), so cardinality is bounded by the route count.
+		path := r.Pattern
+		if path == "" {
+			path = "other"
+		}
+		metrics.HTTPRequestsTotal.WithLabelValues(path, r.Method, status).Inc()
+	})
+}