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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 <list>
#include "mongo/db/catalog/collection.h"
#include "mongo/db/concurrency/locker.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/repl/read_concern_args.h"
#include "mongo/db/s/scoped_collection_metadata.h"
#include "mongo/db/views/view.h"
#include "mongo/s/shard_version.h"
#include "mongo/util/uuid.h"
namespace mongo {
struct PlacementConcern {
boost::optional<DatabaseVersion> dbVersion;
boost::optional<ShardVersion> shardVersion;
};
struct AcquisitionPrerequisites {
enum PlacementConcernPlaceholder {
/**
* Special PlacementConcern which mimics direct connection to a shard, causing the
* acquisition to bypass any sharding checks and acquire just the local catalog portion. Any
* sharding service values, such as the description or the filter are not allowed to be used
* (will invariant).
*
* Note the *with potential data loss* in the name, which indicates that it allows the
* caller to operate on a collection which is not even on the local shard, thus if used
* incorrectly can lead to data loss.
*/
kLocalCatalogOnlyWithPotentialDataLoss,
};
using PlacementConcernVariant = stdx::variant<PlacementConcern, PlacementConcernPlaceholder>;
enum ViewMode { kMustBeCollection, kCanBeView };
enum OperationType { kRead, kWrite };
AcquisitionPrerequisites(NamespaceString nss,
boost::optional<UUID> uuid,
PlacementConcernVariant placementConcern,
OperationType operationType,
ViewMode viewMode)
: nss(std::move(nss)),
uuid(std::move(uuid)),
placementConcern(std::move(placementConcern)),
operationType(operationType),
viewMode(viewMode) {}
NamespaceString nss;
boost::optional<UUID> uuid;
PlacementConcernVariant placementConcern;
OperationType operationType;
ViewMode viewMode;
};
namespace shard_role_details {
struct AcquiredCollection {
AcquisitionPrerequisites prerequisites;
std::shared_ptr<Lock::DBLock> dbLock;
boost::optional<Lock::CollectionLock> collectionLock;
boost::optional<ScopedCollectionDescription> collectionDescription;
boost::optional<ScopedCollectionFilter> ownershipFilter;
CollectionPtr collectionPtr;
};
struct AcquiredView {
AcquisitionPrerequisites prerequisites;
std::shared_ptr<Lock::DBLock> dbLock;
boost::optional<Lock::CollectionLock> collectionLock;
std::shared_ptr<const ViewDefinition> viewDefinition;
};
/**
* This class is a container for all the collection resources which are currently acquired by a
* given operation. Operations consist of one or more transactions, which "acquire" and "release"
* collections within their lifetime.
*
* Transactions start either explicitly (through the construction of a WUOW) or implicitly, from the
* moment the first collection is acquired. They last until the last collection snapshot is released
* or the WriteUnitOfWork commits (whichever is longer).
*
* Because of the above definition, within a transaction, acquisitions are always 2-phase, meaning
* that acquiring a collection and then releasing it will defer the release until the transaction
* actually commits. The boundaries of the transaction are considered to be the WUOW. If there is no
* WUOW, the transaction ends when the snapshot is released.
*
* There are three steps associated with each acquisition:
*
* - Locking: Acquiring the necessary lock manager locks in order to ensure stability of the
* snapshot for the duration of the acquisition.
* - Snapshotting: Taking a consistent snapshot across all the "services" associated with the
* collection (shard filter, storage catalog, data snapshot).
* - Resource reservation: This is service-specific and indicates setting the necessary state so
* that the snapshot is consistent for the duration of the acquisition. Example of resource
* acquisition is the RangePreserver, which blocks orphan cleanups.
*
* Acquiring a collection performs all three steps: locking, resource reservation and snapshotting.
*
* Releasing a collection performs the inverse of acquisition, freeing locks, reservations and the
* snapshot, such that a new acquire may see newer state (if the readConcern of the transaction
* permits it).
*
* Yielding *all* transaction resources only frees locks and the snapshot, but it keeps the resource
* reservations.
*
* Restoring *all* transaction resources only performs locking and snapshotting (in accordance with
* the read concern of the operation).
*/
struct TransactionResources {
TransactionResources(repl::ReadConcernArgs readConcern);
TransactionResources(TransactionResources&&) = delete;
TransactionResources& operator=(TransactionResources&&) = delete;
TransactionResources(TransactionResources&) = delete;
TransactionResources& operator=(TransactionResources&) = delete;
~TransactionResources();
AcquiredCollection& addAcquiredCollection(AcquiredCollection&& acquiredCollection) {
return acquiredCollections.emplace_back(std::move(acquiredCollection));
}
void releaseCollection(UUID uuid);
const AcquiredView& addAcquiredView(AcquiredView&& acquiredView) {
return acquiredViews.emplace_back(std::move(acquiredView));
}
void releaseAllResourcesOnCommitOrAbort() noexcept;
/**
* Asserts that this transaction context is not holding any collection acquisitions (i.e., it is
* pristine). Used for invarianting in places where we do not expect an existing snapshot to
* have been acquired because the caller expects to operate on latest.
*/
void assertNoAcquiredCollections() const;
// The read concern with which the whole operation started. Remains the same for the duration of
// the entire operation.
repl::ReadConcernArgs readConcern;
// Indicates whether yield has been performed on these resources
bool yielded{false};
////////////////////////////////////////////////////////////////////////////////////////
// Global resources (cover all collections for the operation)
// Set of locks acquired by the operation or nullptr if yielded.
std::unique_ptr<Locker> locker;
// If '_locker' has been yielded, contains a snapshot of the locks which have been yielded.
// Otherwise boost::none.
boost::optional<Locker::LockSnapshot> lockSnapshot;
// The storage engine snapshot associated with this transaction (when yielded).
struct YieldedRecoveryUnit {
std::unique_ptr<RecoveryUnit> recoveryUnit;
WriteUnitOfWork::RecoveryUnitState recoveryUnitState;
};
boost::optional<YieldedRecoveryUnit> yieldRecoveryUnit;
////////////////////////////////////////////////////////////////////////////////////////
// Per-collection resources
// Set of all collections which are currently acquired
std::list<AcquiredCollection> acquiredCollections;
std::list<AcquiredView> acquiredViews;
};
} // namespace shard_role_details
} // namespace mongo
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