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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 <memory>
namespace mongo {
class OperationContext;
/**
* The WriteUnitOfWork is an RAII type that begins a storage engine write unit of work on both the
* Locker and the RecoveryUnit of the OperationContext. Any writes that occur during the lifetime of
* this object will be committed when commit() is called, and rolled back (aborted) when the object
* is destructed without a call to commit() or release().
*
* A WriteUnitOfWork can be nested with others, but only the top level WriteUnitOfWork will commit
* the unit of work on the RecoveryUnit. If a low level WriteUnitOfWork aborts, any parents will
* also abort.
*
* The WriteUnitOfWork may be used in read only mode, where it allows callbacks to be registered
* with the RecoveryUnit and executes them on commit/abort without opening any unit of work on the
* RecoveryUnit. This can be used to unify code that performs in-memory writes using the callback
* functionality of the RecoveryUnit.
*/
class WriteUnitOfWork {
WriteUnitOfWork(const WriteUnitOfWork&) = delete;
WriteUnitOfWork& operator=(const WriteUnitOfWork&) = delete;
public:
/**
* The RecoveryUnitState is used to ensure valid state transitions.
*/
enum RecoveryUnitState {
kNotInUnitOfWork, // not in a unit of work, no writes allowed
kActiveUnitOfWork, // in a unit of work that still may either commit or abort
kFailedUnitOfWork // in a unit of work that has failed and must be aborted
};
WriteUnitOfWork(OperationContext* opCtx, bool groupOplogEntries = false);
~WriteUnitOfWork();
/**
* Creates a top-level WriteUnitOfWork without changing RecoveryUnit or Locker state. For use
* when the RecoveryUnit and Locker are in active or failed state.
*/
static std::unique_ptr<WriteUnitOfWork> createForSnapshotResume(OperationContext* opCtx,
RecoveryUnitState ruState);
/**
* Releases the OperationContext RecoveryUnit and Locker objects from management without
* changing state. Allows for use of these objects beyond the WriteUnitOfWork lifespan. Prepared
* units of work are not allowed be released. Returns the state of the RecoveryUnit.
*/
RecoveryUnitState release();
/**
* Transitions the WriteUnitOfWork to the "prepared" state. The RecoveryUnit state in the
* OperationContext must be active. The WriteUnitOfWork may not be nested and will invariant in
* that case. Will throw CommandNotSupported if the storage engine does not support prepared
* transactions. May throw WriteConflictException.
*
* No subsequent operations are allowed except for commit or abort (when the object is
* destructed).
*/
void prepare();
/**
* Commits the WriteUnitOfWork. If this is the top level unit of work, the RecoveryUnit's unit
* of work is committed. Commit can only be called once on an active unit of work, and may not
* be called on a released WriteUnitOfWork.
*/
void commit();
private:
WriteUnitOfWork() = default; // for createForSnapshotResume
OperationContext* _opCtx;
bool _toplevel;
bool _groupOplogEntries;
bool _committed = false;
bool _prepared = false;
bool _released = false;
};
std::ostream& operator<<(std::ostream& os, WriteUnitOfWork::RecoveryUnitState state);
} // namespace mongo
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