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/**
* Copyright (C) 2020-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 "mongo/client/sdam/sdam_datatypes.h"
#include "mongo/client/sdam/topology_listener.h"
#include "mongo/executor/task_executor.h"
#include "mongo/util/net/hostandport.h"
namespace mongo {
/**
* Manages server monitoring for a single server. Broadcasts the RTT (Round Trip Time) to a
* listener.
*/
class SingleServerPingMonitor : public std::enable_shared_from_this<SingleServerPingMonitor> {
public:
explicit SingleServerPingMonitor(sdam::ServerAddress hostAndPort,
sdam::TopologyListener* rttListener,
Milliseconds pingFrequency,
std::shared_ptr<executor::TaskExecutor> executor);
/**
* Starts the pinging loop.
*/
void init();
/**
* Signals that the SingleServerPingMonitor has been dropped and should cancel any outstanding
* pings scheduled to execute in the future. Contract: Once drop() is completed, the
* SingleServerPingMonitor will stop broadcasting results to the listener.
*/
void drop();
private:
Date_t now() const {
return _executor ? _executor->now() : Date_t::now();
}
/**
* Wraps the callback and schedules it to run at some time.
*
* The callback wrapper does the following:
* * Returns before running cb if isDropped is true.
* * Returns before running cb if the handle was canceled.
* * Locks before running cb and unlocks after.
*/
template <typename Callback>
auto _scheduleWorkAt(Date_t when, Callback&& cb) const;
/**
* Schedules the next ping request at _nextPingStartDate.
*/
void _scheduleServerPing();
/**
* Sends a ping to the server and processes the response. If the ping was successful, broadcasts
* the RTT (Round Trip Time) and schedules the next ping. Otherwise, broadcasts the error status
* and returns.
*/
void _doServerPing();
sdam::ServerAddress _hostAndPort;
/**
* Listens for when new RTT (Round Trip Time) values are published.
*/
sdam::TopologyListener* _rttListener;
/**
* The frequency at which ping requests should be sent to measure the round trip time.
*/
Milliseconds _pingFrequency;
std::shared_ptr<executor::TaskExecutor> _executor;
/**
* The time at which the next ping should be scheduled. Pings should be sent uniformly across
* time at _pingFrequency.
*/
Date_t _nextPingStartDate{};
static constexpr auto kLogLevel = 0;
/**
* Must be held to access any of the member variables below.
*/
mutable Mutex _mutex = MONGO_MAKE_LATCH("SingleServerPingMonitor::mutex");
/**
* Enables a scheduled or outgoing ping to be cancelled upon drop().
*/
executor::TaskExecutor::CallbackHandle _pingHandle;
/**
* Indicates if the server has been dropped and should no longer be monitored.
*/
bool _isDropped = false;
};
/**
* Monitors the RTT (Round Trip Time) for a set of servers.
*/
class ServerPingMonitor : public sdam::TopologyListener {
ServerPingMonitor(const ServerPingMonitor&) = delete;
ServerPingMonitor& operator=(const ServerPingMonitor&) = delete;
public:
ServerPingMonitor(sdam::TopologyListener* rttListener,
Milliseconds pingFrequency,
std::shared_ptr<executor::TaskExecutor> executor);
~ServerPingMonitor();
/**
* Drops all SingleServerMonitors and shuts down the task executor.
*/
void shutdown();
/**
* The first isMaster exchange for a connection to the server succeeded. Creates a new
* SingleServerPingMonitor to monitor the new replica set member.
*/
void onServerHandshakeCompleteEvent(sdam::IsMasterRTT durationMs,
const sdam::ServerAddress& address,
const BSONObj reply = BSONObj());
/**
* Drop corresponding SingleServerPingMonitors if the server is not included in the
* newDescritpion.
*/
void onTopologyDescriptionChangedEvent(UUID topologyId,
sdam::TopologyDescriptionPtr previousDescription,
sdam::TopologyDescriptionPtr newDescription);
private:
/**
* Listens for when new RTT (Round Trip Time) values are published.
*/
sdam::TopologyListener* _rttListener;
/**
* The interval at which ping requests should be sent to measure the RTT (Round Trip Time).
*/
Milliseconds _pingFrequency;
/**
* Executor for performing server monitoring pings for all of the replica set members.
*/
std::shared_ptr<executor::TaskExecutor> _executor;
static constexpr auto kLogLevel = 0;
mutable Mutex _mutex = MONGO_MAKE_LATCH("ServerPingMonitor::mutex");
/**
* Maps each server to a SingleServerPingMonitor.
* Note: SingleServerPingMonitor's drop() should always be called before removing it from the
* _serverPingMonitorMap.
*/
stdx::unordered_map<sdam::ServerAddress, std::shared_ptr<SingleServerPingMonitor>>
_serverPingMonitorMap;
bool _isShutdown{false};
};
} // namespace mongo
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