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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 <boost/optional.hpp>
#include <map>
#include "mongo/db/s/transaction_coordinator.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/util/concurrency/with_lock.h"
namespace mongo {
/**
* This class is a registry for all the active TransactionCoordinator objects, indexed by lsid and
* txnNumber. It supports holding several coordinator objects per session.
*/
class TransactionCoordinatorCatalog {
TransactionCoordinatorCatalog(const TransactionCoordinatorCatalog&) = delete;
TransactionCoordinatorCatalog& operator=(const TransactionCoordinatorCatalog&) = delete;
public:
TransactionCoordinatorCatalog();
~TransactionCoordinatorCatalog();
/**
* Marks that recovery of the catalog has completed and that operations can be run on it.
*/
void exitStepUp(Status status);
/**
* Cancels any outstanding idle transaction coordinators so that they will get unregistered.
*/
void onStepDown();
/**
* Inserts a coordinator to be tracked by the catalog.
*
* Duplicate lsid + txnNumber are not legal and will lead to invariant. The consumer of this
* class (TransactionCoordinatorService) guarantees this will not happen through the following
* means:
* - At step-up recovery time - the catalog starts empty and the coordinators inserted are read
* from the `config.coordinators` collection, which only contains unique entries
* - At regular run time - the session check-out mechanism guarantees that calls to get,
* followed by insert are atomic for the same lsid + txnNumber
*/
void insert(OperationContext* opCtx,
const LogicalSessionId& lsid,
TxnNumber txnNumber,
std::shared_ptr<TransactionCoordinator> coordinator,
bool forStepUp = false);
/**
* Returns the coordinator with the given session id and transaction number, if it exists. If it
* does not exist, return nullptr.
*/
std::shared_ptr<TransactionCoordinator> get(OperationContext* opCtx,
const LogicalSessionId& lsid,
TxnNumber txnNumber);
/**
* Returns the coordinator with the highest transaction number with the given session id, if it
* exists. If it does not exist, return boost::none.
*/
boost::optional<std::pair<TxnNumber, std::shared_ptr<TransactionCoordinator>>>
getLatestOnSession(OperationContext* opCtx, const LogicalSessionId& lsid);
/**
* Blocking method, which waits for all coordinators registered on the catalog to complete
* (after this returns, it is guaranteed that all onCompletion futures have been set)
*/
void join();
/**
* Returns a string representation of the map from LogicalSessionId to the list of TxnNumbers
* with TransactionCoordinators currently in the catalog.
*/
std::string toString() const;
using FilterPredicate =
std::function<bool(const LogicalSessionId lsid,
const TxnNumber txnNumber,
const std::shared_ptr<TransactionCoordinator> transactionCoordinator)>;
using FilterVisitor =
std::function<void(const LogicalSessionId lsid,
const TxnNumber txnNumber,
const std::shared_ptr<TransactionCoordinator> transactionCoordinator)>;
void filter(FilterPredicate predicate, FilterVisitor visitor);
private:
// Map of transaction coordinators, ordered in decreasing transaction number with the most
// recent transaction at the front
using TransactionCoordinatorMap =
std::map<TxnNumber, std::shared_ptr<TransactionCoordinator>, std::greater<TxnNumber>>;
/**
* Blocks in an interruptible wait until the catalog is not marked as having a stepup in
* progress.
*/
void _waitForStepUpToComplete(stdx::unique_lock<stdx::mutex>& lk, OperationContext* opCtx);
/**
* Removes the coordinator with the given session id and transaction number from the catalog, if
* one exists, and if this the last coordinator in the catalog, signals that there are no active
* coordinators.
*
* Note: The coordinator must be in a state suitable for removal (i.e. committed or aborted).
*/
void _remove(const LogicalSessionId& lsid, TxnNumber txnNumber);
/**
* Constructs a string representation of all the coordinators registered on the catalog.
*/
std::string _toString(WithLock wl) const;
// Protects the state below.
mutable stdx::mutex _mutex;
// Contains TransactionCoordinator objects by session id and transaction number. May contain
// more than one coordinator per session. All coordinators for a session that do not correspond
// to the latest transaction should either be in the process of committing or aborting.
LogicalSessionIdMap<TransactionCoordinatorMap> _coordinatorsBySession;
// Stores the result of the coordinator catalog's recovery attempt (the status passed to
// exitStepUp). This is what the values mean:
//
// stepUpCompletionStatus = none - brand new created object (exitStepUp has not been called
// yet). All calls will block.
// stepUpCompletionStatus = OK - recovery completed successfully, transactions can be
// coordinated
// stepUpCompletionStatus = error - recovery completed with an error, transactions cannot be
// coordinated (all methods will fail with this error)
boost::optional<Status> _stepUpCompletionStatus;
// Signaled when recovery of the catalog completes (when _stepUpCompletionStatus transitions
// from none to either OK or error)
stdx::condition_variable _stepUpCompleteCV;
// Notified when the last coordinator is removed from the catalog.
stdx::condition_variable _noActiveCoordinatorsCV;
};
} // namespace mongo
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