config

type Config struct {
	// NodeID is a non-zero value used to identify a node within a Raft cluster.
	NodeID uint64
	// ClusterID is the unique value used to identify a Raft cluster.
	ClusterID uint64
	// IsObserver indicates whether this is an observer Raft node without voting
	// power.
	IsObserver bool
	// CheckQuorum specifies whether the leader node should periodically check
	// non-leader node status and step down to become a follower node when it no
	// longer has the quorum.
	CheckQuorum bool
	// Quiesce specifies whether to let the Raft cluster enter quiesce mode when
	// there is no cluster activity.
	Quiesce bool
	// ElectionRTT is the minimum number of message RTT between elections. Message
	// RTT is defined by NodeHostConfig.RTTMillisecond. The Raft paper suggests it
	// to be a magnitude greater than HeartbeatRTT, which is the interval between
	// two heartbeats. In Raft, the actual interval between elections is
	// randomized to be between ElectionRTT and 2 * ElectionRTT.
	//
	// As an example, assuming NodeHostConfig.RTTMillisecond is 100 millisecond,
	// to set the election interval to be 1 second, then ElectionRTT should be set
	// to 10.
	//
	// When CheckQuorum is enabled, ElectionRTT also defines the interval for
	// checking leader quorum.
	ElectionRTT uint64
	// HeartbeatRTT is the number of message RTT between heartbeats. Message
	// RTT is defined by NodeHostConfig.RTTMillisecond. The Raft paper suggest the
	// heartbeat interval to be close to the average RTT between nodes.
	HeartbeatRTT uint64
	// SnapshotEntries defines how often state machine should be snapshotted
	// defined in terms of number of applied entries. Set SnapshotEntries to 0 to
	// disable Raft snapshotting and log compaction.
	SnapshotEntries uint64
	// CompactionOverhead defines the number of most recent entries to keep after
	// Raft log compaction.
	CompactionOverhead uint64
	// OrderedConfigChange determines whether Raft membership change is enforced
	// with ordered config change ID.
	OrderedConfigChange bool
}

type LogDBFactoryFunc func(dirs []string,
	lowLatencyDirs []string) (raftio.ILogDB, error)

type NodeHostConfig struct {
	// DeploymentID is used to determine whether two NodeHost instances belong to
	// the same deployment and thus allowed to communicate with each other. This
	// helps to prvent accidentially misconfigured NodeHost instances to cause
	// data corruption errors by sending out of context messages to unrelated
	// Raft nodes.
	// For a particular dragonboat based application, you can set DeploymentID
	// to the same uint64 value on all production NodeHost instances, then use
	// different DeploymentID values on your staging and dev environment. It is
	// also recommended to use different DeploymentID values for different
	// dragonboat based applications.
	// When not set, the default value 0 will be used as the deployment ID and
	// thus allowing all NodeHost instances with deployment ID 0 to communicate
	// with each other.
	DeploymentID uint64
	// WALDir is the directory used for storing the WAL of Raft entries. It is
	// recommended to use low latency storage such as NVME SSD with power loss
	// protection to store such WAL data. Leave WALDir to have zero value will
	// have everything stored in NodeHostDir.
	WALDir string
	// NodeHostDir is where everything else is stored.
	NodeHostDir string
	// RTTMillisecond defines the average Rround Trip Time (RTT) in milliseconds
	// between two NodeHost instances. Such a RTT interval is internally used as
	// a logical clock tick, Raft heartbeat and election intervals are both
	// defined in term of how many such RTT intervals.
	// Note that RTTMillisecond is the combined delays between two NodeHost
	// instances including all delays caused by network transmission, delays
	// caused by NodeHost queuing and processing. As an example, when fully
	// loaded, the average Rround Trip Time between two of our NodeHost instances
	// used for benchmarking purposes is up to 500 microseconds when the ping time
	// between them is 100 microseconds.
	RTTMillisecond uint64
	// RaftAddress is a hostname:port address used by the Raft RPC module for
	// exchanging Raft messages. This is also the identifier value to identify
	// a NodeHost instance.
	RaftAddress string
	// APIAddress is the address used by the optional NodeHost RPC API. Empty
	// value means NodeHost API RPC server is not used. This optional field
	// only need to be set when using Master servers.
	APIAddress string
	// MasterServers is a list of Master server addresses to use. Master servers
	// are optional component. Empty or nil value means that there is no Master
	// server configured for this deployment.
	MasterServers []string
	// MutualTLS defines whether to use mutual TLS for authenticating servers
	// and clients. Insecure communication is used when MutualTLS is set to
	// False.
	// See https://github.com/lni/dragonboat/wiki/TLS-in-Dragonboat for more
	// details on how to use Mutual TLS.
	MutualTLS bool
	// CAFile is the path of the CA certificate file. This field is ignored when
	// MutualTLS is false.
	CAFile string
	// CertFile is the path of the node certificate file. This field is ignored
	// when MutualTLS is false.
	CertFile string
	// KeyFile is the path of the node key file. This field is ignored when
	// MutualTLS is false.
	KeyFile string
	// LogDBFactory is the factory function used for creating the Log DB instance
	// used by NodeHost. The default zero value causes the default built-in RocksDB
	// based Log DB implementation to be used.
	LogDBFactory LogDBFactoryFunc
	// RaftRPCFactory is the factory function used for creating the Raft RPC
	// instance for exchanging Raft message between NodeHost instances. The default
	// zero value causes the built-in TCP based RPC module to be used.
	RaftRPCFactory RaftRPCFactoryFunc
}

type RaftRPCFactoryFunc func(NodeHostConfig,
	raftio.RequestHandler, raftio.ChunkSinkFactory) raftio.IRaftRPC