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/**
* Copyright (C) 2014 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 <string>
#include <vector>
#include "mongo/bson/timestamp.h"
#include "mongo/db/repl/last_vote.h"
#include "mongo/db/repl/member_heartbeat_data.h"
#include "mongo/db/repl/member_state.h"
#include "mongo/db/repl/optime.h"
#include "mongo/db/repl/repl_set_config.h"
#include "mongo/db/repl/replication_coordinator.h"
#include "mongo/db/repl/topology_coordinator.h"
#include "mongo/db/server_options.h"
#include "mongo/util/time_support.h"
namespace mongo {
class OperationContext;
namespace rpc {
class ReplSetMetadata;
} // namespace rpc
namespace repl {
static const Milliseconds UninitializedPing{-1};
/**
* Represents a latency measurement for each replica set member based on heartbeat requests.
* The measurement is an average weighted 80% to the old value, and 20% to the new value.
*
* Also stores information about heartbeat progress and retries.
*/
class PingStats {
public:
/**
* Records that a new heartbeat request started at "now".
*
* This resets the failure count used in determining whether the next request to a target
* should be a retry or a regularly scheduled heartbeat message.
*/
void start(Date_t now);
/**
* Records that a heartbeat request completed successfully, and that "millis" milliseconds
* were spent for a single network roundtrip plus remote processing time.
*/
void hit(Milliseconds millis);
/**
* Records that a heartbeat request failed.
*/
void miss();
/**
* Gets the number of hit() calls.
*/
unsigned int getCount() const {
return count;
}
/**
* Gets the weighted average round trip time for heartbeat messages to the target.
* Returns 0 if there have been no pings recorded yet.
*/
Milliseconds getMillis() const {
return value == UninitializedPing ? Milliseconds(0) : value;
}
/**
* Gets the date at which start() was last called, which is used to determine if
* a heartbeat should be retried or if the time limit has expired.
*/
Date_t getLastHeartbeatStartDate() const {
return _lastHeartbeatStartDate;
}
/**
* Gets the number of failures since start() was last called.
*
* This value is incremented by calls to miss(), cleared by calls to start() and
* set to the maximum possible value by calls to hit().
*/
int getNumFailuresSinceLastStart() const {
return _numFailuresSinceLastStart;
}
private:
unsigned int count = 0;
Milliseconds value = UninitializedPing;
Date_t _lastHeartbeatStartDate;
int _numFailuresSinceLastStart = std::numeric_limits<int>::max();
};
class TopologyCoordinatorImpl : public TopologyCoordinator {
public:
struct Options {
// A sync source is re-evaluated after it lags behind further than this amount.
Seconds maxSyncSourceLagSecs{0};
// Whether or not this node is running as a config server.
ClusterRole clusterRole{ClusterRole::None};
};
/**
* Constructs a Topology Coordinator object.
**/
TopologyCoordinatorImpl(Options options);
////////////////////////////////////////////////////////////
//
// Implementation of TopologyCoordinator interface
//
////////////////////////////////////////////////////////////
virtual Role getRole() const;
virtual MemberState getMemberState() const;
virtual HostAndPort getSyncSourceAddress() const;
virtual std::vector<HostAndPort> getMaybeUpHostAndPorts() const;
virtual int getMaintenanceCount() const;
virtual long long getTerm();
virtual UpdateTermResult updateTerm(long long term, Date_t now);
virtual void setForceSyncSourceIndex(int index);
virtual HostAndPort chooseNewSyncSource(Date_t now,
const OpTime& lastOpTimeFetched,
ChainingPreference chainingPreference) override;
virtual void blacklistSyncSource(const HostAndPort& host, Date_t until);
virtual void unblacklistSyncSource(const HostAndPort& host, Date_t now);
virtual void clearSyncSourceBlacklist();
virtual bool shouldChangeSyncSource(const HostAndPort& currentSource,
const OpTime& myLastOpTime,
const rpc::ReplSetMetadata& replMetadata,
boost::optional<rpc::OplogQueryMetadata> oqMetadata,
Date_t now) const;
virtual bool becomeCandidateIfStepdownPeriodOverAndSingleNodeSet(Date_t now);
virtual void setElectionSleepUntil(Date_t newTime);
virtual void setFollowerMode(MemberState::MS newMode);
virtual void adjustMaintenanceCountBy(int inc);
virtual void prepareSyncFromResponse(const HostAndPort& target,
const OpTime& lastOpApplied,
BSONObjBuilder* response,
Status* result);
virtual void prepareFreshResponse(const ReplicationCoordinator::ReplSetFreshArgs& args,
Date_t now,
const OpTime& lastOpApplied,
BSONObjBuilder* response,
Status* result);
virtual void prepareElectResponse(const ReplicationCoordinator::ReplSetElectArgs& args,
Date_t now,
const OpTime& lastOpApplied,
BSONObjBuilder* response,
Status* result);
virtual Status prepareHeartbeatResponse(Date_t now,
const ReplSetHeartbeatArgs& args,
const std::string& ourSetName,
const OpTime& lastOpApplied,
const OpTime& lastOpDurable,
ReplSetHeartbeatResponse* response);
virtual Status prepareHeartbeatResponseV1(Date_t now,
const ReplSetHeartbeatArgsV1& args,
const std::string& ourSetName,
const OpTime& lastOpApplied,
const OpTime& lastOpDurable,
ReplSetHeartbeatResponse* response);
virtual void prepareStatusResponse(const ReplSetStatusArgs& rsStatusArgs,
BSONObjBuilder* response,
Status* result);
virtual void fillIsMasterForReplSet(IsMasterResponse* response);
virtual StatusWith<PrepareFreezeResponseResult> prepareFreezeResponse(Date_t now,
int secs,
BSONObjBuilder* response);
virtual void updateConfig(const ReplSetConfig& newConfig,
int selfIndex,
Date_t now,
const OpTime& lastOpApplied);
virtual std::pair<ReplSetHeartbeatArgs, Milliseconds> prepareHeartbeatRequest(
Date_t now, const std::string& ourSetName, const HostAndPort& target);
virtual std::pair<ReplSetHeartbeatArgsV1, Milliseconds> prepareHeartbeatRequestV1(
Date_t now, const std::string& ourSetName, const HostAndPort& target);
virtual HeartbeatResponseAction processHeartbeatResponse(
Date_t now,
Milliseconds networkRoundTripTime,
const HostAndPort& target,
const StatusWith<ReplSetHeartbeatResponse>& hbResponse,
const OpTime& myLastOpApplied);
virtual bool voteForMyself(Date_t now);
virtual void setElectionInfo(OID electionId, Timestamp electionOpTime);
virtual void processWinElection(OID electionId, Timestamp electionOpTime);
virtual void processLoseElection();
virtual Status checkShouldStandForElection(Date_t now, const OpTime& lastOpApplied) const;
virtual void setMyHeartbeatMessage(const Date_t now, const std::string& message);
virtual bool stepDown(Date_t until,
bool force,
const OpTime& lastOpApplied,
const OpTime& lastOpCommitted);
virtual bool stepDownIfPending();
virtual bool isStepDownPending() const;
virtual Date_t getStepDownTime() const;
virtual rpc::ReplSetMetadata prepareReplSetMetadata(const OpTime& lastVisibleOpTime,
const OpTime& lastCommitttedOpTime) const;
virtual rpc::OplogQueryMetadata prepareOplogQueryMetadata(const OpTime& lastCommittedOpTime,
const OpTime& lastAppliedOpTime,
int rbid) const;
virtual void processReplSetRequestVotes(const ReplSetRequestVotesArgs& args,
ReplSetRequestVotesResponse* response,
const OpTime& lastAppliedOpTime);
virtual void summarizeAsHtml(ReplSetHtmlSummary* output);
virtual void loadLastVote(const LastVote& lastVote);
virtual void voteForMyselfV1();
virtual void prepareForStepDown();
virtual void setPrimaryIndex(long long primaryIndex);
virtual HeartbeatResponseAction setMemberAsDown(Date_t now,
const int memberIndex,
const OpTime& myLastOpApplied);
virtual Status becomeCandidateIfElectable(const Date_t now,
const OpTime& lastOpApplied,
bool isPriorityTakeover);
virtual void setStorageEngineSupportsReadCommitted(bool supported);
////////////////////////////////////////////////////////////
//
// Test support methods
//
////////////////////////////////////////////////////////////
// Changes _memberState to newMemberState. Only for testing.
void changeMemberState_forTest(const MemberState& newMemberState,
const Timestamp& electionTime = Timestamp(0, 0));
// Sets "_electionTime" to "newElectionTime". Only for testing.
void _setElectionTime(const Timestamp& newElectionTime);
// Sets _currentPrimaryIndex to the given index. Should only be used in unit tests!
// TODO(spencer): Remove this once we can easily call for an election in unit tests to
// set the current primary.
void _setCurrentPrimaryForTest(int primaryIndex);
// Returns _electionTime. Only used in unittests.
Timestamp getElectionTime() const;
// Returns _electionId. Only used in unittests.
OID getElectionId() const;
// Returns _currentPrimaryIndex. Only used in unittests.
int getCurrentPrimaryIndex() const;
private:
enum UnelectableReason {
None = 0,
CannotSeeMajority = 1 << 0,
NotCloseEnoughToLatestOptime = 1 << 1,
ArbiterIAm = 1 << 2,
NotSecondary = 1 << 3,
NoPriority = 1 << 4,
StepDownPeriodActive = 1 << 5,
NoData = 1 << 6,
NotInitialized = 1 << 7,
VotedTooRecently = 1 << 8,
RefusesToStand = 1 << 9,
NotCloseEnoughToLatestForPriorityTakeover = 1 << 10,
};
typedef int UnelectableReasonMask;
// Returns the number of heartbeat pings which have occurred.
int _getTotalPings();
// Returns the current "ping" value for the given member by their address
Milliseconds _getPing(const HostAndPort& host);
// Determines if we will veto the member specified by "args.id", given that the last op
// we have applied locally is "lastOpApplied".
// If we veto, the errmsg will be filled in with a reason
bool _shouldVetoMember(const ReplicationCoordinator::ReplSetFreshArgs& args,
const Date_t& now,
const OpTime& lastOpApplied,
std::string* errmsg) const;
// Returns the index of the member with the matching id, or -1 if none match.
int _getMemberIndex(int id) const;
// Sees if a majority number of votes are held by members who are currently "up"
bool _aMajoritySeemsToBeUp() const;
// Returns true if the node can see a healthy primary of equal or greater priority to the
// candidate.
bool _canSeeHealthyPrimaryOfEqualOrGreaterPriority(const int candidateIndex) const;
// Is otherOpTime close enough (within 10 seconds) to the latest known optime to qualify
// for an election
bool _isOpTimeCloseEnoughToLatestToElect(const OpTime& otherOpTime,
const OpTime& ourLastOpApplied) const;
// Is our optime close enough to the latest known optime to call for a priority takeover.
bool _amIFreshEnoughForPriorityTakeover(const OpTime& ourLastOpApplied) const;
// Returns reason why "self" member is unelectable
UnelectableReasonMask _getMyUnelectableReason(const Date_t now,
const OpTime& lastOpApplied,
bool isPriorityTakeover) const;
// Returns reason why memberIndex is unelectable
UnelectableReasonMask _getUnelectableReason(int memberIndex, const OpTime& lastOpApplied) const;
// Returns the nice text of why the node is unelectable
std::string _getUnelectableReasonString(UnelectableReasonMask ur) const;
// Return true if we are currently primary
bool _iAmPrimary() const;
// Scans through all members that are 'up' and return the latest known optime.
OpTime _latestKnownOpTime(const OpTime& ourLastOpApplied) const;
// Scans the electable set and returns the highest priority member index
int _getHighestPriorityElectableIndex(Date_t now, const OpTime& lastOpApplied) const;
// Returns true if "one" member is higher priority than "two" member
bool _isMemberHigherPriority(int memberOneIndex, int memberTwoIndex) const;
// Helper shortcut to self config
const MemberConfig& _selfConfig() const;
// Returns NULL if there is no primary, or the MemberConfig* for the current primary
const MemberConfig* _currentPrimaryMember() const;
/**
* Performs updating "_currentPrimaryIndex" for processHeartbeatResponse(), and determines if an
* election or stepdown should commence.
* _updatePrimaryFromHBDataV1() is a simplified version of _updatePrimaryFromHBData() to be used
* when in ProtocolVersion1.
*/
HeartbeatResponseAction _updatePrimaryFromHBData(int updatedConfigIndex,
const MemberState& originalState,
Date_t now,
const OpTime& lastOpApplied);
HeartbeatResponseAction _updatePrimaryFromHBDataV1(int updatedConfigIndex,
const MemberState& originalState,
Date_t now,
const OpTime& lastOpApplied);
/**
* Updates _hbdata based on the newConfig, ensuring that every member in the newConfig
* has an entry in _hbdata. If any nodes in the newConfig are also present in
* _currentConfig, copies their heartbeat info into the corresponding entry in the updated
* _hbdata vector.
*/
void _updateHeartbeatDataForReconfig(const ReplSetConfig& newConfig, int selfIndex, Date_t now);
void _stepDownSelfAndReplaceWith(int newPrimary);
/**
* Looks up the provided member in the blacklist and returns true if the member's blacklist
* expire time is after 'now'. If the member is found but the expire time is before 'now',
* the function returns false. If the member is not found in the blacklist, the function
* returns false.
**/
bool _memberIsBlacklisted(const MemberConfig& memberConfig, Date_t now) const;
// This node's role in the replication protocol.
Role _role;
// This is a unique id that is generated and set each time we transition to PRIMARY, as the
// result of an election.
OID _electionId;
// The time at which the current PRIMARY was elected.
Timestamp _electionTime;
// This node's election term. The term is used as part of the consensus algorithm to elect
// and maintain one primary (leader) node in the cluster.
long long _term;
// the index of the member we currently believe is primary, if one exists, otherwise -1
int _currentPrimaryIndex;
// the hostandport we are currently syncing from
// empty if no sync source (we are primary, or we cannot connect to anyone yet)
HostAndPort _syncSource;
// These members are not chosen as sync sources for a period of time, due to connection
// issues with them
std::map<HostAndPort, Date_t> _syncSourceBlacklist;
// The next sync source to be chosen, requested via a replSetSyncFrom command
int _forceSyncSourceIndex;
// Options for this TopologyCoordinator
Options _options;
// "heartbeat message"
// sent in requestHeartbeat respond in field "hbm"
std::string _hbmsg;
Date_t _hbmsgTime; // when it was logged
// heartbeat msg to send to others; descriptive diagnostic info
std::string _getHbmsg(Date_t now) const;
int _selfIndex; // this node's index in _members and _currentConfig
ReplSetConfig _rsConfig; // The current config, including a vector of MemberConfigs
// heartbeat data for each member. It is guaranteed that this vector will be maintained
// in the same order as the MemberConfigs in _currentConfig, therefore the member config
// index can be used to index into this vector as well.
std::vector<MemberHeartbeatData> _hbdata;
// Indicates that we've received a request to stepdown from PRIMARY (likely via a heartbeat)
bool _stepDownPending;
// Time when stepDown command expires
Date_t _stepDownUntil;
// A time before which this node will not stand for election.
// In protocol version 1, this is used to prevent running for election after seeing
// a new term.
Date_t _electionSleepUntil;
// The number of calls we have had to enter maintenance mode
int _maintenanceModeCalls;
// The sub-mode of follower that we are in. Legal values are RS_SECONDARY, RS_RECOVERING,
// RS_STARTUP2 (initial sync) and RS_ROLLBACK. Only meaningful if _role == Role::follower.
// Configured via setFollowerMode(). If the sub-mode is RS_SECONDARY, then the effective
// sub-mode is either RS_SECONDARY or RS_RECOVERING, depending on _maintenanceModeCalls.
// Rather than accesing this variable direclty, one should use the getMemberState() method,
// which computes the replica set node state on the fly.
MemberState::MS _followerMode;
typedef std::map<HostAndPort, PingStats> PingMap;
// Ping stats for each member by HostAndPort;
PingMap _pings;
// Last vote info from the election
struct VoteLease {
static const Seconds leaseTime;
Date_t when;
int whoId = -1;
HostAndPort whoHostAndPort;
} _voteLease;
// V1 last vote info for elections
LastVote _lastVote{OpTime::kInitialTerm, -1};
enum class ReadCommittedSupport {
kUnknown,
kNo,
kYes,
};
// Whether or not the storage engine supports read committed.
ReadCommittedSupport _storageEngineSupportsReadCommitted{ReadCommittedSupport::kUnknown};
};
} // namespace repl
} // namespace mongo
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