A configuration defines the servers that are part of the cluster. More...

#include <RaftConsensus.h>

Classes
struct	SimpleConfiguration
	A list of servers in which a simple majority constitutes a quorum. More...
Public Types
enum	State { BLANK, STABLE, STAGING, TRANSITIONAL }
	See state. More...
typedef std::shared_ptr< Server >	ServerRef
typedef std::function< bool(Server &)>	Predicate
typedef std::function < uint64_t(Server &)>	GetValue
typedef std::function< void(Server &)>	SideEffect
Public Member Functions
	Configuration (uint64_t serverId, RaftConsensus &consensus)
	Constructor.
	~Configuration ()
	Destructor.
void	forEach (const SideEffect &sideEffect)
	Apply a function to every known server, including the local, old, new, and staging servers.
bool	hasVote (ServerRef server) const
	Return true if the given server may be part of a quorum, false otherwise.
std::string	lookupAddress (uint64_t serverId) const
	Lookup the network addresses for a particular server (comma-delimited).
bool	quorumAll (const Predicate &predicate) const
	Return true if there exists a quorum for which every server satisfies the predicate, false otherwise.
uint64_t	quorumMin (const GetValue &getValue) const
	Return the smallest value of any server in the quorum of servers that have the largest values.
void	resetStagingServers ()
	Remove the staging servers, if any.
void	reset ()
	Set the state of this object as if it had just been constructed.
void	setConfiguration (uint64_t newId, const Protocol::Raft::Configuration &newDescription)
	Set the configuration.
void	setStagingServers (const Protocol::Raft::SimpleConfiguration &stagingServers)
	Add servers that are to mirror the log but that may not have a vote (listeners).
bool	stagingAll (const Predicate &predicate) const
	Return true if every server in the staging set satisfies the predicate, false otherwise.
uint64_t	stagingMin (const GetValue &getValue) const
	Return the smallest value of any server in the staging set.
void	updateServerStats (Protocol::ServerStats &serverStats, Core::Time::SteadyTimeConverter &time) const
	Write the configuration servers' state into the given structure.
Public Attributes
std::shared_ptr< LocalServer >	localServer
	This server.
State	state
	Specifies the meaning of oldServers and newServers.
uint64_t	id
	The ID of the current configuration.
Protocol::Raft::Configuration	description
	A description of the current configuration.
Private Member Functions
ServerRef	getServer (uint64_t newServerId)
	If no server by the given ID is known, construct a new one.
Private Attributes
RaftConsensus &	consensus
	Used for constructing Server instances.
std::unordered_map< uint64_t, ServerRef >	knownServers
	A map from server ID to Server of every server, including the local, previous, new, and staging servers.
SimpleConfiguration	oldServers
	A majority of these servers are necessary for a quorum under STABLE, STAGING, and TRANSITIONAL configurations.
SimpleConfiguration	newServers
	A majority of these servers are necessary for a quorum under TRANSITIONAL configurations.
Friends
class	Invariants
std::ostream &	operator<< (std::ostream &os, State state)
	Print out a State for debugging purposes.
std::ostream &	operator<< (std::ostream &os, const Configuration &configuration)
	Print out a Configuration for debugging purposes.

Detailed Description

A configuration defines the servers that are part of the cluster.

This class does not do any internal locking; it should be accessed only while holding the RaftConsensus lock.

Definition at line 483 of file RaftConsensus.h.

Member Typedef Documentation

typedef std::shared_ptr<Server> LogCabin::Server::RaftConsensusInternal::Configuration::ServerRef

Definition at line 485 of file RaftConsensus.h.

typedef std::function<bool(Server&)> LogCabin::Server::RaftConsensusInternal::Configuration::Predicate

Definition at line 486 of file RaftConsensus.h.

typedef std::function<uint64_t(Server&)> LogCabin::Server::RaftConsensusInternal::Configuration::GetValue

Definition at line 487 of file RaftConsensus.h.

typedef std::function<void(Server&)> LogCabin::Server::RaftConsensusInternal::Configuration::SideEffect

Definition at line 488 of file RaftConsensus.h.

Member Enumeration Documentation

enum LogCabin::Server::RaftConsensusInternal::Configuration::State

See state.

Enumerator:

BLANK	The configuration specifies no servers. Servers that are new to the cluster and have empty logs start in this state.
STABLE	The configuration specifies a single list of servers: a quorum requires any majority of this list.
STAGING	The configuration specifies two lists of servers: a quorum requires any majority of the first list, but the servers in the second list also receive log entries.
TRANSITIONAL	The configuration specifies two lists of servers: a quorum requires any majority of the first list and any majority of the second.

Definition at line 510 of file RaftConsensus.h.

Constructor & Destructor Documentation

LogCabin::Server::RaftConsensusInternal::Configuration::Configuration	(	uint64_t	serverId,
		RaftConsensus &	consensus
	)

Constructor.

Definition at line 480 of file RaftConsensus.cc.

LogCabin::Server::RaftConsensusInternal::Configuration::~Configuration ( )

Destructor.

Definition at line 494 of file RaftConsensus.cc.

Member Function Documentation

void LogCabin::Server::RaftConsensusInternal::Configuration::forEach ( const SideEffect & sideEffect )

Apply a function to every known server, including the local, old, new, and staging servers.

The function will only be called once for each server, even if a server exists in more than one of these categories.

Definition at line 499 of file RaftConsensus.cc.

bool LogCabin::Server::RaftConsensusInternal::Configuration::hasVote ( ServerRef server ) const

Return true if the given server may be part of a quorum, false otherwise.

Definition at line 506 of file RaftConsensus.cc.

std::string LogCabin::Server::RaftConsensusInternal::Configuration::lookupAddress ( uint64_t serverId ) const

Lookup the network addresses for a particular server (comma-delimited).

Returns empty string if not found.

Definition at line 517 of file RaftConsensus.cc.

bool LogCabin::Server::RaftConsensusInternal::Configuration::quorumAll ( const Predicate & predicate ) const

Return true if there exists a quorum for which every server satisfies the predicate, false otherwise.

Definition at line 526 of file RaftConsensus.cc.

uint64_t LogCabin::Server::RaftConsensusInternal::Configuration::quorumMin ( const GetValue & getValue ) const

Return the smallest value of any server in the quorum of servers that have the largest values.

Returns:: Largest value for which every server in a quorum has a value greater than or equal to this one. 0 if the configuration is BLANK.

Definition at line 537 of file RaftConsensus.cc.

void LogCabin::Server::RaftConsensusInternal::Configuration::resetStagingServers ( )

Remove the staging servers, if any.

Return to the configuration state prior to a preceding call to setStagingServers.

Definition at line 548 of file RaftConsensus.cc.

void LogCabin::Server::RaftConsensusInternal::Configuration::reset ( )

Set the state of this object as if it had just been constructed.

Definition at line 565 of file RaftConsensus.cc.

void LogCabin::Server::RaftConsensusInternal::Configuration::setConfiguration	(	uint64_t	newId,
		const Protocol::Raft::Configuration &	newDescription
	)

Set the configuration.

Any existing staging servers are dropped.

Parameters:

newId	The log entry ID of the configuration.
newDescription	The IDs and addresses of the servers in the configuration. If any newServers are listed in the description, it is considered TRANSITIONAL; otherwise, it is STABLE.

Definition at line 580 of file RaftConsensus.cc.

void LogCabin::Server::RaftConsensusInternal::Configuration::setStagingServers ( const Protocol::Raft::SimpleConfiguration & stagingServers )

Add servers that are to mirror the log but that may not have a vote (listeners).

This can only be called on a STABLE configuration and makes it STAGING. TODO(ongaro): that might be a sign of a poor interface. descriptions should probably have three sets, as john said.

Definition at line 632 of file RaftConsensus.cc.

bool LogCabin::Server::RaftConsensusInternal::Configuration::stagingAll ( const Predicate & predicate ) const

Return true if every server in the staging set satisfies the predicate, false otherwise.

Definition at line 647 of file RaftConsensus.cc.

uint64_t LogCabin::Server::RaftConsensusInternal::Configuration::stagingMin ( const GetValue & getValue ) const

Return the smallest value of any server in the staging set.

Returns:: Minimum value on any server in the staging set, or 0 if the staging set is empty.

Definition at line 656 of file RaftConsensus.cc.

void LogCabin::Server::RaftConsensusInternal::Configuration::updateServerStats	(	Protocol::ServerStats &	serverStats,
		Core::Time::SteadyTimeConverter &	time
	)		const