text: /**
   *    Copyright (C) 2022-present MongoDB, Inc.
   *
   *    This program is free software: you can redistribute it and/or modify
   *    it under the terms of the Server Side Public License, version 1,
   *    as published by MongoDB, Inc.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    Server Side Public License for more details.
   *
   *    You should have received a copy of the Server Side Public License
   *    along with this program. If not, see
   *    <http://www.mongodb.com/licensing/server-side-public-license>.
   *
   *    As a special exception, the copyright holders give permission to link the
   *    code of portions of this program with the OpenSSL library under certain
   *    conditions as described in each individual source file and distribute
   *    linked combinations including the program with the OpenSSL library. You
   *    must comply with the Server Side Public License in all respects for
   *    all of the code used other than as permitted herein. If you modify file(s)
   *    with this exception, you may extend this exception to your version of the
   *    file(s), but you are not obligated to do so. If you do not wish to do so,
   *    delete this exception statement from your version. If you delete this
   *    exception statement from all source files in the program, then also delete
   *    it in the license file.
   */
  
  #pragma once
  
  #include "mongo/base/status.h"
  #include "mongo/db/concurrency/lock_manager_defs.h"
  #include "mongo/db/service_context.h"
  
  #include <memory>
  
  namespace mongo {
  
  class TicketHolder;
  
  class TicketHolders {
  public:
      static Status updateConcurrentWriteTransactions(const int& newWriteTransactions);
  
      static Status updateConcurrentReadTransactions(const int& newReadTransactions);
  
      static TicketHolders& get(ServiceContext* svcCtx);
      static TicketHolders& get(ServiceContext& svcCtx);
      /**
       * Sets the TicketHolder implementation to use to obtain tickets from 'reading' (for MODE_S and
       * MODE_IS), and from 'writing' (for MODE_IX) in order to throttle database access. There is no
       * throttling for MODE_X, as there can only ever be a single locker using this mode. The
       * throttling is intended to defend against large drops in throughput under high load due to too
       * much concurrency.
       */
      void setGlobalThrottling(std::unique_ptr<TicketHolder> reading,
                               std::unique_ptr<TicketHolder> writing);
  
      TicketHolder* getTicketHolder(LockMode mode);
  
  private:
      std::unique_ptr<TicketHolder> _openWriteTransaction;
      std::unique_ptr<TicketHolder> _openReadTransaction;
  };
  
  }  // namespace mongo
  