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/**
* Copyright (C) 2019-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 <functional>
#include <memory>
#include <vector>
#include "mongo/client/sdam/server_description.h"
#include "mongo/client/sdam/topology_description.h"
#include "mongo/platform/mutex.h"
namespace mongo::sdam {
// Actions that mutate the state of the topology description via events.
using TransitionAction = std::function<void(TopologyDescription&, const ServerDescriptionPtr&)>;
// indexed by ServerType
using StateTransitionTableRow = std::vector<TransitionAction>;
/**
* StateTransitionTable[t][s] returns the action to
* take given that the topology currently has type t, and we receive a ServerDescription
* with type s.
*/
using StateTransitionTable = std::vector<StateTransitionTableRow>;
class TopologyStateMachine {
public:
TopologyStateMachine(const SdamConfiguration& config);
/**
* Provides input to the state machine, and triggers the correct action based on the current
* TopologyDescription and the incoming ServerDescription. The topologyDescription instance may
* be modified as a result.
*/
void onServerDescription(TopologyDescription& topologyDescription,
const ServerDescriptionPtr& serverDescription);
private:
void initTransitionTable();
// State machine actions
// These are implemented, in an almost verbatim fashion, from the description
// here:
// https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#actions
void updateUnknownWithStandalone(TopologyDescription&, const ServerDescriptionPtr&);
void updateRSWithoutPrimary(TopologyDescription&, const ServerDescriptionPtr&);
void updateRSWithPrimaryFromMember(TopologyDescription&, const ServerDescriptionPtr&);
void updateRSFromPrimary(TopologyDescription&, const ServerDescriptionPtr&);
void removeAndStopMonitoring(TopologyDescription&, const ServerDescriptionPtr&);
void checkIfHasPrimary(TopologyDescription&, const ServerDescriptionPtr&);
void removeAndCheckIfHasPrimary(TopologyDescription&, const ServerDescriptionPtr&);
void setTopologyTypeAndUpdateRSWithoutPrimary(TopologyDescription&,
const ServerDescriptionPtr&);
TransitionAction setTopologyTypeAction(TopologyType type);
TransitionAction setTopologyTypeAndUpdateRSFromPrimary(TopologyType type);
void addUnknownServers(TopologyDescription& topologyDescription,
const ServerDescriptionPtr& serverDescription);
// The functions below mutate the state of the topology description
void installServerDescription(TopologyDescription& topologyDescription,
ServerDescriptionPtr newServerDescription,
bool newServer);
void removeServerDescription(TopologyDescription& topologyDescription,
HostAndPort serverAddress);
void modifyTopologyType(TopologyDescription& topologyDescription, TopologyType topologyType);
void modifySetName(TopologyDescription& topologyDescription,
const boost::optional<std::string>& setName);
void modifyMaxElectionId(TopologyDescription& topologyDescription, const OID& newMaxElectionId);
void modifyMaxSetVersion(TopologyDescription& topologyDescription, int& newMaxSetVersion);
StateTransitionTable _stt;
SdamConfiguration _config;
};
using TopologyStateMachinePtr = std::unique_ptr<TopologyStateMachine>;
} // namespace mongo::sdam
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