[#1658] node: Validate RPC limiter configuration

Validate that configured limits match the methods registered earlier.

Signed-off-by: Aleksey Savchuk <a.savchuk@yadro.com>

cmd/frostfs-node/grpc.go

@@ -240,6 +240,10 @@ func initRPCLimiter(c *cfg) error {
 		limits = append(limits, limiting.KeyLimit{Keys: l.Methods, Limit: l.MaxOps})
 	}
 
+	if err := validateRPCLimits(c, limits); err != nil {
+		return fmt.Errorf("validate RPC limits: %w", err)
+	}
+
 	limiter, err := limiting.NewSemaphoreLimiter(limits)
 	if err != nil {
 		return fmt.Errorf("create RPC limiter: %w", err)
@@ -248,3 +252,35 @@ func initRPCLimiter(c *cfg) error {
 	c.cfgGRPC.limiter.Store(limiter)
 	return nil
 }
+
+func validateRPCLimits(c *cfg, limits []limiting.KeyLimit) error {
+	availableMethods := getAvailableMethods(c.cfgGRPC.servers)
+	for _, limit := range limits {
+		for _, method := range limit.Keys {
+			if _, ok := availableMethods[method]; !ok {
+				return fmt.Errorf("set limit on an unknown method %q", method)
+			}
+		}
+	}
+	return nil
+}
+
+func getAvailableMethods(servers []grpcServer) map[string]struct{} {
+	res := make(map[string]struct{})
+	for _, server := range servers {
+		for _, method := range getMethodsForServer(server.Server) {
+			res[method] = struct{}{}
+		}
+	}
+	return res
+}
+
+func getMethodsForServer(server *grpc.Server) []string {
+	var res []string
+	for service, info := range server.GetServiceInfo() {
+		for _, method := range info.Methods {
+			res = append(res, fmt.Sprintf("/%s/%s", service, method.Name))
+		}
+	}
+	return res
+}