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/**
 *    Copyright (C) 2018-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/platform/mutex.h"
#include "mongo/s/sessions_collection_sharded.h"

namespace mongo {

class OperationContext;

/**
 * Accesses the sessions collection for config servers.
 */
class SessionsCollectionConfigServer : public SessionsCollectionSharded {
public:
    /**
     * Ensures that the sessions collection has been set up for this cluster, sharded, and with the
     * proper indexes.
     *
     * This method may safely be called multiple times and if called concurrently the calls will get
     * serialised using the mutex below.
     *
     * If there are no shards in this cluster, this method will do nothing.
     */
    void setupSessionsCollection(OperationContext* opCtx) override;

private:
    void _shardCollectionIfNeeded(OperationContext* opCtx);
    void _generateIndexesIfNeeded(OperationContext* opCtx);

    // Serialises concurrent calls to setupSessionsCollection so that only one thread performs the
    // sharded operations
    Mutex _mutex = MONGO_MAKE_LATCH("SessionsCollectionConfigServer::_mutex");
};

}  // namespace mongo