raft

Documentation

Index

• Constants
• func DPrintVerbose(format string, a ...interface{}) (n int, err error)
• func DPrintf(format string, a ...interface{}) (n int, err error)
• type AppendEntriesArgs
• type AppendEntriesReply
• type ApplyMsg
• type Entry
  • func (e *Entry) String() string
• type Log
  • func (l *Log) String() string
• type Persister
  • func MakePersister() *Persister
  • func (ps *Persister) Copy() *Persister
  • func (ps *Persister) RaftStateSize() int
  • func (ps *Persister) ReadRaftState() []byte
  • func (ps *Persister) ReadSnapshot() []byte
  • func (ps *Persister) SaveRaftState(state []byte)
  • func (ps *Persister) SaveStateAndSnapshot(state []byte, snapshot []byte)
  • func (ps *Persister) SnapshotSize() int
• type Raft
  • func Make(peers []*labrpc.ClientEnd, me int, persister *Persister, applyCh chan ApplyMsg) *Raft
  • func (rf *Raft) AppendEntries(args *AppendEntriesArgs, reply *AppendEntriesReply)
  • func (rf *Raft) CondInstallSnapshot(lastIncludedTerm int, lastIncludedIndex int, snapshot []byte) bool
  • func (rf *Raft) GetState() (int, bool)
  • func (rf *Raft) Kill()
  • func (rf *Raft) RequestVote(args *RequestVoteArgs, reply *RequestVoteReply)
  • func (rf *Raft) Snapshot(index int, snapshot []byte)
  • func (rf *Raft) Start(command interface{}) (int, int, bool)
• type RaftState
• type RequestVoteArgs
• type RequestVoteReply

Constants

const (
	Follower  RaftState = "Follower"
	Candidate           = "Candidate"
	Leader              = "Leader"
)

const Debug = false

Debugging

const SnapShotInterval = 10

Functions

func DPrintVerbose

func DPrintVerbose(format string, a ...interface{}) (n int, err error)

func DPrintf

func DPrintf(format string, a ...interface{}) (n int, err error)

Types

type AppendEntriesArgs

type AppendEntriesArgs struct {
	Term         int
	LeaderId     int
	PrevLogIndex int
	PrevLogTerm  int
	Entries      []Entry
	LeaderCommit int
}

type AppendEntriesReply

type AppendEntriesReply struct {
	Term     int
	Success  bool
	Conflict bool
	XTerm    int
	XIndex   int
	XLen     int
}

type ApplyMsg

type ApplyMsg struct {
	CommandValid bool
	Command      interface{}
	CommandIndex int

	// For 2D:
	SnapshotValid bool
	Snapshot      []byte
	SnapshotTerm  int
	SnapshotIndex int
}

as each Raft peer becomes aware that successive log entries are committed, the peer should send an ApplyMsg to the service (or tester) on the same server, via the applyCh passed to Make(). set CommandValid to true to indicate that the ApplyMsg contains a newly committed log entry.

in part 2D you'll want to send other kinds of messages (e.g., snapshots) on the applyCh, but set CommandValid to false for these other uses.

type Entry

type Entry struct {
	Command interface{}
	Term    int
	Index   int
}

func (*Entry) String

func (e *Entry) String() string

type Log

type Log struct {
	Entries []Entry
	Index0  int
}

func (*Log) String

func (l *Log) String() string

type Persister

type Persister struct {
	// contains filtered or unexported fields
}

func MakePersister

func MakePersister() *Persister

func (*Persister) Copy

func (ps *Persister) Copy() *Persister

func (*Persister) RaftStateSize

func (ps *Persister) RaftStateSize() int

func (*Persister) ReadRaftState

func (ps *Persister) ReadRaftState() []byte

func (*Persister) ReadSnapshot

func (ps *Persister) ReadSnapshot() []byte

func (*Persister) SaveRaftState

func (ps *Persister) SaveRaftState(state []byte)

func (*Persister) SaveStateAndSnapshot

func (ps *Persister) SaveStateAndSnapshot(state []byte, snapshot []byte)

Save both Raft state and K/V snapshot as a single atomic action, to help avoid them getting out of sync.

func (*Persister) SnapshotSize

func (ps *Persister) SnapshotSize() int

type Raft

type Raft struct {
	// contains filtered or unexported fields
}

A Go object implementing a single Raft peer.

func Make

func Make(peers []*labrpc.ClientEnd, me int,
	persister *Persister, applyCh chan ApplyMsg) *Raft

the service or tester wants to create a Raft server. the ports of all the Raft servers (including this one) are in peers[]. this server's port is peers[me]. all the servers' peers[] arrays have the same order. persister is a place for this server to save its persistent state, and also initially holds the most recent saved state, if any. applyCh is a channel on which the tester or service expects Raft to send ApplyMsg messages. Make() must return quickly, so it should start goroutines for any long-running work.

func (*Raft) AppendEntries

func (rf *Raft) AppendEntries(args *AppendEntriesArgs, reply *AppendEntriesReply)

func (*Raft) CondInstallSnapshot

func (rf *Raft) CondInstallSnapshot(lastIncludedTerm int, lastIncludedIndex int, snapshot []byte) bool

A service wants to switch to snapshot. Only do so if Raft hasn't have more recent info since it communicate the snapshot on applyCh.

func (*Raft) GetState

func (rf *Raft) GetState() (int, bool)

return currentTerm and whether this server believes it is the leader.

func (*Raft) Kill

func (rf *Raft) Kill()

the tester doesn't halt goroutines created by Raft after each test, but it does call the Kill() method. your code can use killed() to check whether Kill() has been called. the use of atomic avoids the need for a lock.

the issue is that long-running goroutines use memory and may chew up CPU time, perhaps causing later tests to fail and generating confusing debug output. any goroutine with a long-running loop should call killed() to check whether it should stop.

func (*Raft) RequestVote

func (rf *Raft) RequestVote(args *RequestVoteArgs, reply *RequestVoteReply)

example RequestVote RPC handler.

func (*Raft) Snapshot

func (rf *Raft) Snapshot(index int, snapshot []byte)

the service says it has created a snapshot that has all info up to and including index. this means the service no longer needs the log through (and including) that index. Raft should now trim its log as much as possible.

func (*Raft) Start

func (rf *Raft) Start(command interface{}) (int, int, bool)

the service using Raft (e.g. a k/v server) wants to start agreement on the next command to be appended to Raft's log. if this server isn't the leader, returns false. otherwise start the agreement and return immediately. there is no guarantee that this command will ever be committed to the Raft log, since the leader may fail or lose an election. even if the Raft instance has been killed, this function should return gracefully.

the first return value is the index that the command will appear at if it's ever committed. the second return value is the current term. the third return value is true if this server believes it is the leader.

type RaftState

type RaftState string

type RequestVoteArgs

type RequestVoteArgs struct {
	// Your data here (2A, 2B).
	Term         int
	CandidateId  int
	LastLogIndex int
	LastLogTerm  int
}

example RequestVote RPC arguments structure. field names must start with capital letters!

type RequestVoteReply

type RequestVoteReply struct {
	// Your data here (2A).
	Term        int
	VoteGranted bool
}

example RequestVote RPC reply structure. field names must start with capital letters!