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/**
* 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 "mongo/db/storage/ticketholder_monitor.h"
#include "mongo/util/concurrency/ticketholder.h"
namespace mongo {
class TicketHolder;
/**
* A ticket mechanism is required for global lock acquisition to reduce contention on storage engine
* resources.
*
* Each TicketHolder maintains a pool of n available tickets. The TicketHolderManager is responsible
* for sizing each ticket pool and determining which ticket pool a caller should use for ticket
* acquisition.
*
*/
class TicketHolderManager {
public:
TicketHolderManager(ServiceContext* svcCtx,
std::unique_ptr<TicketHolder> readTicketHolder,
std::unique_ptr<TicketHolder> writeTicketHolder);
~TicketHolderManager(){};
static Status updateConcurrentWriteTransactions(const int32_t& newWriteTransactions);
static Status updateConcurrentReadTransactions(const int32_t& newReadTransactions);
// The 'lowPriorityAdmissionBypassThreshold' is only applicable when ticket admission is
// controlled via PriorityTicketHolders.
//
// Returns Status::OK() and updates the 'lowPriorityAdmissionBypassThreshold' provided all
// TicketHolders are initialized and of type PriorityTicketHolders. Otherwise, returns an error.
static Status updateLowPriorityAdmissionBypassThreshold(const int32_t& newBypassThreshold);
static TicketHolderManager* get(ServiceContext* svcCtx);
static void use(ServiceContext* svcCtx,
std::unique_ptr<TicketHolderManager> newTicketHolderManager);
/**
* Validates whether whether the given name is a valid concurrency adjustment algorithm name.
*/
static Status validateConcurrencyAdjustmentAlgorithm(const std::string& name,
const boost::optional<TenantId>&);
/**
* Given the 'mode' a user requests for a GlobalLock, returns the corresponding TicketHolder.
*/
TicketHolder* getTicketHolder(LockMode mode);
void appendStats(BSONObjBuilder& b);
private:
/**
* Holds tickets for MODE_S/MODE_IS global locks requests.
*/
std::unique_ptr<TicketHolder> _readTicketHolder;
/**
* Holds tickets for MODE_X/MODE_IX global lock requests.
*/
std::unique_ptr<TicketHolder> _writeTicketHolder;
/**
* Task which adjusts the number of concurrent read/write transactions.
*/
std::unique_ptr<TicketHolderMonitor> _monitor;
};
} // namespace mongo
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