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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 <string>
#include "mongo/db/catalog_raii.h"
#include "mongo/db/stats/top.h"
#include "mongo/util/timer.h"
namespace mongo {
/**
* RAII-style class which automatically tracks the operation namespace in CurrentOp and records the
* operation via Top upon destruction.
*/
class AutoStatsTracker {
MONGO_DISALLOW_COPYING(AutoStatsTracker);
public:
/**
* Sets the namespace of the CurOp object associated with 'opCtx' to be 'nss' and starts the
* CurOp timer. 'lockType' describes which type of lock is held by this operation, and will be
* used for reporting via Top. If 'dbProfilingLevel' is not given, this constructor will acquire
* and then drop a database lock in order to determine the database's profiling level.
*/
AutoStatsTracker(OperationContext* opCtx,
const NamespaceString& nss,
Top::LockType lockType,
boost::optional<int> dbProfilingLevel,
Date_t deadline = Date_t::max());
/**
* Records stats about the current operation via Top.
*/
~AutoStatsTracker();
private:
OperationContext* _opCtx;
Top::LockType _lockType;
};
/**
* Same as calling AutoGetCollection with MODE_IS, but in addition ensures that the read will be
* performed against an appropriately committed snapshot if the operation is using a readConcern of
* 'majority'.
*
* Use this when you want to read the contents of a collection, but you are not at the top-level of
* some command. This will ensure your reads obey any requested readConcern, but will not update the
* status of CurrentOp, or add a Top entry.
*
* NOTE: Must not be used with any locks held, because it needs to block waiting on the committed
* snapshot to become available.
*/
class AutoGetCollectionForRead {
MONGO_DISALLOW_COPYING(AutoGetCollectionForRead);
public:
AutoGetCollectionForRead(
OperationContext* opCtx,
const NamespaceStringOrUUID& nsOrUUID,
AutoGetCollection::ViewMode viewMode = AutoGetCollection::ViewMode::kViewsForbidden,
Date_t deadline = Date_t::max());
Database* getDb() const {
return _autoColl->getDb();
}
Collection* getCollection() const {
return _autoColl->getCollection();
}
ViewDefinition* getView() const {
return _autoColl->getView();
}
const NamespaceString& getNss() const {
return _autoColl->getNss();
}
private:
// If this field is set, the reader will not take the ParallelBatchWriterMode lock and conflict
// with secondary batch application. This stays in scope with the _autoColl so that locks are
// taken and released in the right order.
boost::optional<ShouldNotConflictWithSecondaryBatchApplicationBlock>
_shouldNotConflictWithSecondaryBatchApplicationBlock;
// This field is optional, because the code to wait for majority committed snapshot needs to
// release locks in order to block waiting
boost::optional<AutoGetCollection> _autoColl;
// Returns true if we should read at the last applied timestamp instead of at "no" timestamp
// (i.e. reading with the "latest" snapshot reflecting all writes). Reading at the last applied
// timestamp avoids reading in-flux data actively being written by the replication system.
bool _shouldReadAtLastAppliedTimestamp(OperationContext* opCtx,
const NamespaceString& nss,
repl::ReadConcernLevel readConcernLevel) const;
// Returns true if the minSnapshot causes conflicting catalog changes for either the provided
// lastAppliedTimestamp or the point-in-time snapshot of the RecoveryUnit on 'opCtx'.
bool _conflictingCatalogChanges(OperationContext* opCtx,
boost::optional<Timestamp> minSnapshot,
boost::optional<Timestamp> lastAppliedTimestamp) const;
};
/**
* Same as AutoGetCollectionForRead, but in addition will add a Top entry upon destruction and
* ensure the CurrentOp object has the right namespace and has started its timer.
*/
class AutoGetCollectionForReadCommand {
MONGO_DISALLOW_COPYING(AutoGetCollectionForReadCommand);
public:
AutoGetCollectionForReadCommand(
OperationContext* opCtx,
const NamespaceStringOrUUID& nsOrUUID,
AutoGetCollection::ViewMode viewMode = AutoGetCollection::ViewMode::kViewsForbidden,
Date_t deadline = Date_t::max());
Database* getDb() const {
return _autoCollForRead.getDb();
}
Collection* getCollection() const {
return _autoCollForRead.getCollection();
}
ViewDefinition* getView() const {
return _autoCollForRead.getView();
}
const NamespaceString& getNss() const {
return _autoCollForRead.getNss();
}
private:
AutoGetCollectionForRead _autoCollForRead;
AutoStatsTracker _statsTracker;
};
/**
* Opens the database that we want to use and sets the appropriate namespace on the
* current operation.
*/
class OldClientContext {
MONGO_DISALLOW_COPYING(OldClientContext);
public:
OldClientContext(OperationContext* opCtx, const std::string& ns, bool doVersion = true);
~OldClientContext();
Database* db() const {
return _db;
}
/** @return if the db was created by this OldClientContext */
bool justCreated() const {
return _justCreated;
}
private:
friend class CurOp;
const Timer _timer;
OperationContext* const _opCtx;
Database* _db;
bool _justCreated{false};
};
/**
* Returns a MODE_IX LockMode if a read is performed under readConcern level snapshot, or a MODE_IS
* lock otherwise. MODE_IX acquisition will allow a read to participate in two-phase locking.
*/
LockMode getLockModeForQuery(OperationContext* opCtx);
} // namespace mongo
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