initial import

core/httphandler/maxconnshandler.go

@@ -0,0 +1,37 @@
+package httphandler
+
+import (
+	"net/http"
+
+	"zero/core/httplog"
+	"zero/core/logx"
+	"zero/core/syncx"
+)
+
+func MaxConns(n int) func(http.Handler) http.Handler {
+	if n <= 0 {
+		return func(next http.Handler) http.Handler {
+			return next
+		}
+	}
+
+	return func(next http.Handler) http.Handler {
+		latchLimiter := syncx.NewLimit(n)
+
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if latchLimiter.TryBorrow() {
+				defer func() {
+					if err := latchLimiter.Return(); err != nil {
+						logx.Error(err)
+					}
+				}()
+
+				next.ServeHTTP(w, r)
+			} else {
+				httplog.Errorf(r, "Concurrent connections over %d, rejected with code %d",
+					n, http.StatusServiceUnavailable)
+				w.WriteHeader(http.StatusServiceUnavailable)
+			}
+		})
+	}
+}