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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 <functional>
#include <memory>
#include <set>
#include <string>
#include "mongo/base/string_data.h"
#include "mongo/client/mongo_uri.h"
#include "mongo/client/replica_set_change_notifier.h"
#include "mongo/client/replica_set_monitor.h"
#include "mongo/executor/task_executor.h"
#include "mongo/util/concurrency/with_lock.h"
#include "mongo/util/duration.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/time_support.h"
namespace mongo {
class ScanningReplicaSetMonitor : public ReplicaSetMonitor {
ScanningReplicaSetMonitor(const ScanningReplicaSetMonitor&) = delete;
ScanningReplicaSetMonitor& operator=(const ScanningReplicaSetMonitor&) = delete;
public:
class Refresher;
/**
* Defaults to false, meaning that if multiple hosts meet a criteria we pick one at random.
* This is required by the replica set driver spec. Set this to true in tests that need host
* selection to be deterministic.
*
* NOTE: Used by unit-tests only.
*/
static bool useDeterministicHostSelection;
static constexpr auto kExpeditedRefreshPeriod = Milliseconds(500);
static constexpr auto kCheckTimeout = Seconds(5);
ScanningReplicaSetMonitor(const MongoURI& uri);
void init() override;
void drop() override;
SemiFuture<HostAndPort> getHostOrRefresh(
const ReadPreferenceSetting& readPref,
Milliseconds maxWait = kDefaultFindHostTimeout) override;
SemiFuture<std::vector<HostAndPort>> getHostsOrRefresh(
const ReadPreferenceSetting& readPref,
Milliseconds maxWait = kDefaultFindHostTimeout) override;
HostAndPort getPrimaryOrUassert() override;
/*
* For the ScanningReplicaSetMonitor, all the failedHost methods are equivalent.
*/
void failedHost(const HostAndPort& host, const Status& status) override;
void failedHostPreHandshake(const HostAndPort& host,
const Status& status,
BSONObj bson) override;
void failedHostPostHandshake(const HostAndPort& host,
const Status& status,
BSONObj bson) override;
bool isPrimary(const HostAndPort& host) const override;
bool isHostUp(const HostAndPort& host) const override;
int getMinWireVersion() const override;
int getMaxWireVersion() const override;
std::string getName() const override;
std::string getServerAddress() const override;
const MongoURI& getOriginalUri() const override;
bool contains(const HostAndPort& server) const override;
void appendInfo(BSONObjBuilder& b, bool forFTDC = false) const override;
bool isKnownToHaveGoodPrimary() const override;
/**
* Returns the refresh period that is given to all new SetStates.
*/
static Seconds getDefaultRefreshPeriod();
//
// internal types (defined in scanning_replica_set_monitor_internal.h)
//
struct IsMasterReply;
struct ScanState;
struct SetState;
typedef std::shared_ptr<ScanState> ScanStatePtr;
typedef std::shared_ptr<SetState> SetStatePtr;
/**
* Allows tests to set initial conditions and introspect the current state.
*/
explicit ScanningReplicaSetMonitor(const SetStatePtr& initialState);
~ScanningReplicaSetMonitor();
/**
* This is for use in tests using MockReplicaSet to ensure that a full scan completes before
* continuing.
*/
void runScanForMockReplicaSet();
static void disableRefreshRetries_forTest();
static bool areRefreshRetriesDisabledForTest();
private:
Future<std::vector<HostAndPort>> _getHostsOrRefresh(const ReadPreferenceSetting& readPref,
Milliseconds maxWait);
/**
* If no scan is in-progress, this function is responsible for setting up a new scan. Otherwise,
* does nothing.
*/
static void _ensureScanInProgress(const SetStatePtr&);
const SetStatePtr _state;
};
/**
* Refreshes the local view of a replica set.
*
* All logic related to choosing the hosts to contact and updating the SetState based on replies
* lives in this class. Use of this class should always be guarded by SetState::mutex unless in
* single-threaded use by ScanningReplicaSetMonitorTest.
*/
class ScanningReplicaSetMonitor::Refresher {
public:
explicit Refresher(const SetStatePtr& setState);
struct NextStep {
enum StepKind {
CONTACT_HOST, /// Contact the returned host
WAIT, /// Wait on condition variable and try again.
DONE, /// No more hosts to contact in this Refresh round
};
explicit NextStep(StepKind step, const HostAndPort& host = HostAndPort())
: step(step), host(host) {}
StepKind step;
HostAndPort host;
};
/**
* Returns the next step to take.
*
* By calling this, you promise to call receivedIsMaster or failedHost if the NextStep is
* CONTACT_HOST.
*/
NextStep getNextStep();
/**
* Call this if a host returned from getNextStep successfully replied to an isMaster call.
* Negative latencyMicros are ignored.
*/
void receivedIsMaster(const HostAndPort& from, int64_t latencyMicros, const BSONObj& reply);
/**
* Call this if a host returned from getNextStep failed to reply to an isMaster call.
*/
void failedHost(const HostAndPort& host, const Status& status);
/**
* Starts a new scan over the hosts in set.
*/
void startNewScan();
/**
* First, checks that the "reply" is not from a stale primary by comparing the electionId of
* "reply" to the maxElectionId recorded by the SetState and returns OK status if "reply"
* belongs to a non-stale primary. Otherwise returns a failed status.
*
* The 'from' parameter specifies the node from which the response is received.
*
* Updates _set and _scan based on set-membership information from a master.
* Applies _scan->unconfirmedReplies to confirmed nodes.
* Does not update this host's node in _set->nodes.
*/
Status receivedIsMasterFromMaster(const HostAndPort& from, const IsMasterReply& reply);
/**
* Schedules isMaster requests to all hosts that currently need to be contacted.
* Does nothing if requests have already been sent to all known hosts.
*/
void scheduleNetworkRequests();
void scheduleIsMaster(const HostAndPort& host);
private:
// Both pointers are never NULL
SetStatePtr _set;
ScanStatePtr _scan; // May differ from _set->currentScan if a new scan has started.
};
} // namespace mongo
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