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/**
* Copyright (C) 2014 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/disallow_copying.h"
#include "mongo/base/status.h"
#include "mongo/base/string_data.h"
#include "mongo/db/storage/recovery_unit.h"
#include "mongo/db/concurrency/locker.h"
#include "mongo/db/concurrency/d_concurrency.h"
namespace mongo {
class Client;
class CurOp;
class ProgressMeter;
/**
* This class encompasses the state required by an operation.
*
* TODO(HK): clarify what this means. There's one OperationContext for one user operation...
* but is this true for getmore? Also what about things like fsyncunlock / internal
* users / etc.?
*
* On construction, an OperationContext associates itself with the current client, and only on
* destruction it deassociates itself. At any time a client can be associated with at most one
* OperationContext.
*/
class OperationContext {
MONGO_DISALLOW_COPYING(OperationContext);
public:
virtual ~OperationContext() { }
/**
* Interface for durability. Caller DOES NOT own pointer.
*/
virtual RecoveryUnit* recoveryUnit() const = 0;
/**
* Returns the RecoveryUnit (same return value as recoveryUnit()) but the caller takes
* ownership of the returned RecoveryUnit, and the OperationContext instance relinquishes
* ownership. Sets the RecoveryUnit to NULL.
*
* Used to transfer ownership of storage engine state from OperationContext
* to ClientCursor for getMore-able queries.
*
* Note that we don't allow the top-level locks to be stored across getMore.
* We rely on active cursors being killed when collections or databases are dropped,
* or when collection metadata changes.
*/
virtual RecoveryUnit* releaseRecoveryUnit() = 0;
virtual void setRecoveryUnit(RecoveryUnit* unit) = 0;
/**
* Interface for locking. Caller DOES NOT own pointer.
*/
virtual Locker* lockState() const = 0;
// --- operation level info? ---
/**
* If the thread is not interrupted, returns Status::OK(), otherwise returns the cause
* for the interruption. The throw variant returns a user assertion corresponding to the
* interruption status.
*/
virtual void checkForInterrupt() const = 0;
virtual Status checkForInterruptNoAssert() const = 0;
/**
* Delegates to CurOp, but is included here to break dependencies.
* Caller does not own the pointer.
*/
virtual ProgressMeter* setMessage(const char* msg,
const std::string& name = "Progress",
unsigned long long progressMeterTotal = 0,
int secondsBetween = 3) = 0;
/**
* Delegates to CurOp, but is included here to break dependencies.
*
* TODO: We return a string because of hopefully transient CurOp thread-unsafe insanity.
*/
virtual string getNS() const = 0;
/**
* Returns true if this operation is under a GodScope. Only used by DBDirectClient.
* TODO(spencer): SERVER-10228 Remove this
*/
virtual bool isGod() const = 0;
/**
* Returns the client under which this context runs.
*/
virtual Client* getClient() const = 0;
/**
* Returns CurOp. Caller does not own pointer
*/
virtual CurOp* getCurOp() const = 0;
/**
* Returns the operation ID associated with this operation.
* WARNING: Due to SERVER-14995, this OpID is not guaranteed to stay the same for the
* lifetime of this OperationContext.
*/
virtual unsigned int getOpID() const = 0;
/**
* @return true if this instance is primary for this namespace
*/
virtual bool isPrimaryFor( const StringData& ns ) = 0;
protected:
OperationContext() { }
};
class WriteUnitOfWork {
MONGO_DISALLOW_COPYING(WriteUnitOfWork);
public:
WriteUnitOfWork(OperationContext* txn)
: _txn(txn),
_ended(false) {
if ( _txn->lockState() ) {
_txn->lockState()->beginWriteUnitOfWork();
}
_txn->recoveryUnit()->beginUnitOfWork();
}
~WriteUnitOfWork() {
_txn->recoveryUnit()->endUnitOfWork();
if (_txn->lockState() && !_ended) {
_txn->lockState()->endWriteUnitOfWork();
}
}
void commit() {
invariant(!_ended);
_txn->recoveryUnit()->commitUnitOfWork();
if (_txn->lockState()) {
_txn->lockState()->endWriteUnitOfWork();
_ended = true;
}
}
private:
OperationContext* const _txn;
bool _ended;
};
/**
* RAII-style class to mark the scope of a transaction. ScopedTransactions may be nested.
* An outermost ScopedTransaction calls commitAndRestart() on destruction, so that the storage
* engine can release resources, such as snapshots or locks, that it may have acquired during
* the transaction. Note that any writes are committed in nested WriteUnitOfWork scopes,
* so write conflicts cannot happen on completing a ScopedTransaction.
*
* TODO: The ScopedTransaction should hold the global lock
*/
class ScopedTransaction {
MONGO_DISALLOW_COPYING(ScopedTransaction);
public:
/**
* The mode for the transaction indicates whether the transaction will write (MODE_IX) or
* only read (MODE_IS), or needs to run without other writers (MODE_S) or any other
* operations (MODE_X) on the server.
*/
ScopedTransaction(OperationContext* txn, LockMode mode) : _txn(txn) { }
~ScopedTransaction() {
if (!_txn->lockState()->isLocked()) {
_txn->recoveryUnit()->commitAndRestart();
}
}
private:
OperationContext* _txn;
};
} // namespace mongo
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