config

type CompressionType = pb.CompressionType

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
	// 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
	// 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.
	//
	// As an example, assuming NodeHostConfig.RTTMillisecond is 100 millisecond,
	// to set the heartbeat interval to be every 200 milliseconds, then
	// HeartbeatRTT should be set to 2.
	HeartbeatRTT uint64
	// SnapshotEntries defines how often the state machine should be snapshotted
	// automcatically. It is defined in terms of the number of applied Raft log
	// entries. SnapshotEntries can be set to 0 to disable such automatic
	// snapshotting.
	//
	// When SnapshotEntries is set to N, it means a snapshot is created for
	// roughly every N applied Raft log entries (proposals). This also implies
	// that sending N log entries to a follower is more expensive than sending a
	// snapshot.
	//
	// Once a snapshot is generated, Raft log entries covered by the new snapshot
	// can be compacted. This involves two steps, redundant log entries are first
	// marked as deleted, then they are physically removed from the underlying
	// storage when a LogDB compaction is issued at a later stage. See the godoc
	// on CompactionOverhead for details on what log entries are actually removed
	// and compacted after generating a snapshot.
	//
	// Once automatic snapshotting is disabled by setting the SnapshotEntries
	// field to 0, users can still use NodeHost's RequestSnapshot or
	// SyncRequestSnapshot methods to manually request snapshots.
	SnapshotEntries uint64
	// CompactionOverhead defines the number of most recent entries to keep after
	// each Raft log compaction. Raft log compaction is performance automatically
	// every time when a snapshot is created.
	//
	// For example, when a snapshot is created at let's say index 10,000, then all
	// Raft log entries with index <= 10,000 can be removed from that node as they
	// have already been covered by the created snapshot image. This frees up the
	// maximum storage space but comes at the cost that the full snapshot will
	// have to be sent to the follower if the follower requires any Raft log entry
	// at index <= 10,000. When CompactionOverhead is set to say 500, Dragonboat
	// then compacts the Raft log up to index 9,500 and keeps Raft log entries
	// between index (9,500, 1,0000]. As a result, the node can still replicate
	// Raft log entries between index (9,500, 1,0000] to other peers and only fall
	// back to stream the full snapshot if any Raft log entry with index <= 9,500
	// is required to be replicated.
	CompactionOverhead uint64
	// OrderedConfigChange determines whether Raft membership change is enforced
	// with ordered config change ID.
	OrderedConfigChange bool
	// MaxInMemLogSize is the target size in bytes allowed for storing in memory
	// Raft logs on each Raft node. In memory Raft logs are the ones that have
	// not been applied yet.
	// MaxInMemLogSize is a target value implemented to prevent unbounded memory
	// growth, it is not for precisely limiting the exact memory usage.
	// When MaxInMemLogSize is 0, the target is set to math.MaxUint64. When
	// MaxInMemLogSize is set and the target is reached, error will be returned
	// when clients try to make new proposals.
	// MaxInMemLogSize is recommended to be significantly larger than the biggest
	// proposal you are going to use.
	MaxInMemLogSize uint64
	// SnapshotCompressionType is the compression type to use for compressing
	// generated snapshot data. No compression is used by default.
	SnapshotCompressionType CompressionType
	// EntryCompressionType is the compression type to use for compressing the
	// payload of user proposals. When Snappy is used, the maximum proposal
	// payload allowed is roughly limited to 3.42GBytes.
	EntryCompressionType CompressionType
	// DisableAutoCompactions disables auto compaction used for reclaiming Raft
	// entry storage spaces. By default, compaction is issued every time when
	// a snapshot is captured, this helps to reclaim disk spaces as soon as
	// possible at the cost of higher IO overhead. Users can disable such auto
	// compactions and use NodeHost.RequestCompaction to manually request such
	// compactions when necessary.
	DisableAutoCompactions bool
	// IsObserver indicates whether this is an observer Raft node without voting
	// power. Described as non-voting members in the section 4.2.1 of Diego
	// Ongaro's thesis, observer nodes are usually used to allow a new node to
	// join the cluster and catch up with other existing ndoes without impacting
	// the availability. Extra observer nodes can also be introduced to serve
	// read-only requests without affecting system write throughput.
	//
	// Observer support is currently experimental.
	IsObserver bool
	// IsWitness indicates whether this is a witness Raft node without actual log
	// replication and do not have state machine. It is mentioned in the section
	// 11.7.2 of Diego Ongaro's thesis.
	//
	// Witness support is currently experimental.
	IsWitness bool
	// Quiesce specifies whether to let the Raft cluster enter quiesce mode when
	// there is no cluster activity. Clusters in quiesce mode do not exchange
	// heartbeat messages to minimize bandwidth consumption.
	//
	// Quiesce support is currently experimental.
	Quiesce bool
}

type IFS = vfs.IFS

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. Set RTTMillisecond to 1 when it is less
	// than 1 million in your environment.
	RTTMillisecond uint64
	// RaftAddress is a hostname:port or IP:port address used by the Raft RPC
	// module for exchanging Raft messages and snapshots. This is also the
	// identifier for a NodeHost instance. RaftAddress should be set to the
	// public address that can be accessed from remote NodeHost instances.
	RaftAddress string
	// ListenAddress is a hostname:port or IP:port address used by the Raft RPC
	// module to listen on for Raft message and snapshots. When the ListenAddress
	// field is not set, The Raft RPC module listens on RaftAddress. If 0.0.0.0
	// is specified as the IP of the ListenAddress, Dragonboat listens to the
	// specified port on all interfaces. When hostname or domain name is
	// specified, it is locally resolved to IP addresses first and Dragonboat
	// listens to all resolved IP addresses.
	ListenAddress 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
	// MaxSendQueueSize is the maximum size in bytes of each send queue.
	// Once the maximum size is reached, further replication messages will be
	// dropped to restrict memory usage. When set to 0, it means the send queue
	// size is unlimited.
	MaxSendQueueSize uint64
	// MaxReceiveQueueSize is the maximum size in bytes of each receive queue.
	// Once the maximum size is reached, further replication messages will be
	// dropped to restrict memory usage. When set to 0, it means the queue size
	// is unlimited.
	MaxReceiveQueueSize uint64
	// 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
	// EnableMetrics determines whether health metrics in Prometheus format should
	// be enabled.
	EnableMetrics bool
	// RaftEventListener is the listener for Raft events, such as Raft leadership
	// change, exposed to user space. NodeHost uses a single dedicated goroutine
	// to invoke all RaftEventListener methods one by one, CPU intensive or IO
	// related procedures that can cause long delays should be offloaded to worker
	// goroutines managed by users. See the raftio.IRaftEventListener definition
	// for more details.
	RaftEventListener raftio.IRaftEventListener
	// MaxSnapshotSendBytesPerSecond defines how much snapshot data can be sent
	// every second for all Raft clusters managed by the NodeHost instance.
	// The default value 0 means there is no limit set for snapshot streaming.
	MaxSnapshotSendBytesPerSecond uint64
	// MaxSnapshotRecvBytesPerSecond defines how much snapshot data can be
	// received each second for all Raft clusters managed by the NodeHost instance.
	// The default value 0 means there is no limit for receiving snapshot data.
	MaxSnapshotRecvBytesPerSecond uint64
	// FS is the filesystem used by tests. Dragonboat applications are not
	// required to explicitly set this field.
	FS IFS
	// SystemEventsListener allows users to be notified for system events such
	// as snapshot creation, log compaction and snapshot streaming. It is usually
	// used for testing purposes or for other advanced usages, Dragonboat
	// applications are not required to explicitly set this field.
	SystemEventListener raftio.ISystemEventListener
	// SystemTickerPrecision is the precision of the system ticker. This value is
	// usually set in tests. Dragonboat applications are not required to
	// explicitly set this field.
	SystemTickerPrecision time.Duration
}

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