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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/db/operation_context.h"
#include "mongo/db/resource_yielder.h"
namespace mongo {
/**
* Implementation of ResourceYielder that yields resources checked out in the course of running a
* distributed transaction.
*/
class TransactionRouterResourceYielder : public ResourceYielder {
public:
/**
* The next two methods return a newly allocated yielder for the given yielding scenario.
*
* Use makeForLocalHandoff() when the operation expected to check out the session next is in the
* same local process, e.g. a mongos command in a transaction is yielding so a command spawned
* by the transaction API can check out the same session.
*
* Use makeForRemoteCommand() when yielding waiting for a possibly remote response to be
* received. If the local process serves both a router and mongod role, the local process may
* need to check out the same session to produce the response.
*
* The only difference in behavior is that makeForLocalHandoff() always returns a yielder and
* makeForRemoteCommand() returns nullptr if the local process is a mongos because a mongos
* cannot target itself.
*/
static std::unique_ptr<TransactionRouterResourceYielder> makeForLocalHandoff();
static std::unique_ptr<TransactionRouterResourceYielder> makeForRemoteCommand();
/**
* If the opCtx has a checked out RouterOperationContextSession, yields it.
*/
void yield(OperationContext* opCtx) override;
/**
* If the opCtx had previously checked out RouterOperationContextSession, checks it back out.
* Note this may throw if the opCtx is interrupted at global shutdown. Otherwise it should never
* fail.
*/
void unyield(OperationContext* opCtx) override;
private:
bool _yielded{false};
};
} // namespace mongo
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