raft

type AppendEntriesArgs struct {
	// leader’s term
	Term uint64
	// so follower can redirect clients
	LeaderId RaftId

	// index of log entry immediately preceding new ones
	PrevLogIndex uint64
	// term of prevLogIndex entry
	PrevLogTerm uint64

	// log entries to store (empty for heartbeat;
	// may send more than one for efficiency)
	Entries []LogEntry

	// leader’s commitIndex
	LeaderCommit uint64
}

type AppendEntriesResults struct {
	// currentTerm
	Term uint64
	// for leader to update itself success true
	// if follower contained entry matching
	Success bool
}

type Apply func(commands Commands) (appliedCount int, err error)

type Command []byte

type Commands interface {
	// 获取命令序列
	Data() []Command
}

type Log interface {
	// Get 获取 raft log 中索引为 index 的 log entry term
	// 若无, 则返回 0, nil
	Get(index uint64) (term uint64, err error)
	// Match 是否有匹配上 term 与 index 的 log entry
	Match(index, term uint64) (bool, error)
	// Last 返回最后一个 log entry 的 term 与 index
	// 若无, 则返回 0 , 0
	Last() (index, term uint64, err error)
	// RangeGet 获取在 (i, j] 索引区间的 log entry
	// 若无, 则返回 nil, nil
	RangeGet(i, j uint64) ([]LogEntry, error)
	// AppendAfter 在afterIndex之后追加 log entry
	AppendAfter(afterIndex uint64, entries ...LogEntry) error
	// Append 追加log entry
	Append(entries ...LogEntry) error
	// AppendEntry 追加一个 log entry , 并返回索引
	AppendEntry(entry LogEntry) (index uint64, err error)
}

type LogEntry struct {
	Index      uint64
	Term       uint64
	Type       LogEntryType
	Command    Command
	AppendTime time.Time
}

type LogEntryType uint8

type Logger interface {
	Debug(format string, args ...interface{})
}

type OptFn func(*opts)

type RPC interface {
	Listen(addr string) error
	Serve() error
	Register(RPCService) error
	Close() error

	CallAppendEntries(addr RaftAddr, args AppendEntriesArgs) (AppendEntriesResults, error)
	CallRequestVote(addr RaftAddr, args RequestVoteArgs) (RequestVoteResults, error)
}

type RPCService interface {
	AppendEntries(args AppendEntriesArgs, results *AppendEntriesResults) error
	RequestVote(args RequestVoteArgs, results *RequestVoteResults) error
}

type Raft interface {
	// Id 获取 raft 一致性模型 id
	Id() RaftId
	// Addr 获取 raft 一致性模型 rpc addr
	Addr() RaftAddr

	// Run 启动 raft 一致性模型
	Run() error
	// Stop 停止 raft 一致性模型
	Stop()
	// Done 是否已经停止
	Done() <-chan struct{}

	// Handle 处理 cmd
	//
	// append log entry --> log replication --> apply to state matchine
	Handle(ctx context.Context, cmd ...Command) error
	// IsLeader 是否是 Leader
	IsLeader() bool

	// ChangeConfig add added and remove removed
	ChangeConfig(ctx context.Context, added []RaftPeer, removed []RaftId) error
}

type RaftAddr string

type RaftId string

type RaftPeer struct {
	Id   RaftId
	Addr RaftAddr
}

type RequestVoteArgs struct {
	// term candidate’s term
	Term uint64
	// candidateId candidate requesting vote
	CandidateId RaftId

	// lastLogIndex index of candidate’s last log entry (§5.4)
	LastLogIndex uint64
	// lastLogTerm term of candidate’s last log entry (§5.4)
	LastLogTerm uint64
}

type RequestVoteResults struct {
	// currentTerm, for candidate to update itself
	Term uint64
	// true means candidate received vote
	VoteGranted bool
}

type Store interface {
	Set(key []byte, val []byte) error
	// Get returns the value for key, or an empty byte slice if key was not found.
	Get(key []byte) ([]byte, error)

	SetUint64(key []byte, val uint64) error
	// GetUint64 returns the uint64 value for key, or 0 if key was not found.
	GetUint64(key []byte) (uint64, error)
}