func leaderFunc(pid int, rserver *rServer, channelClose chan bool, inbox chan *cluster.Envelope, outbox chan *cluster.Envelope, peers []int, debug bool) {
// var nextIndex = make([]int, len(peers))
// var matchIndex = make([]int, len(peers))
innerl:
for {
select {
case <-time.After(time.Millisecond * heartbeatInterval):
// Add the PrevLogTerm in the appendEntries message
var PrevLogTerm int = DEFAULT_TERM
// Read Previous logEntry to get the PrevLogTerm
rserver.ReaderRequest <- &ReadRequest{Index: rserver.CommitIndex - 1}
// Wait for the logEntry to be read
select {
case serverLogEntry := <-rserver.ReaderData:
if debug {
log.Printf("Leader %d read logEntry %v", rserver.Pid, serverLogEntry)
}
if serverLogEntry != nil {
PrevLogTerm = serverLogEntry.ServerLogData.Term
}
}
appendEntries := AppendEntries{Term: rserver.CurrentTerm, LeaderId: pid, PrevLogIndex: rserver.CommitIndex - 1, PrevLogTerm: PrevLogTerm, Entries: nil, LeaderCommit: rserver.CommitIndex}
for peer := range peers {
peerId := peers[peer]
if debug {
log.Printf("Leader %d with term %d Sending alive message to server %d", pid, rserver.CurrentTerm, peerId)
}
outbox <- &cluster.Envelope{Pid: peerId, MsgId: int64(rserver.CurrentTerm), Msg: appendEntries}
}
case message := <-inbox:
switch msg := message.Msg.(type) {
// If a server with higher term comes up then step down as a follwer
case AppendEntries:
if msg.Term > rserver.CurrentTerm {
if debug {
log.Printf("Server %d with term %d is changing state from leader to follower", pid, rserver.CurrentTerm)
}
rserver.RSLeader = false
rserver.State = FOLLOWER
inbox <- message
break innerl
}
case AppendEntriesStatus:
if debug {
log.Printf("leader server %d with term %d Received status message from %d with term %d", pid, rserver.CurrentTerm, message.Pid, msg.Term)
}
if msg.Term >= rserver.CurrentTerm {
if debug {
log.Printf("Server %d with term %d is changing state from leader to follower", pid, rserver.CurrentTerm)
}
rserver.RSLeader = false
rserver.State = FOLLOWER
break innerl
}
case RequestVote:
if msg.Term >= rserver.CurrentTerm && msg.Term != rserver.VotedFor {
if debug {
log.Printf("Leader %d with term %d is changing state from leader to follower", pid, rserver.CurrentTerm)
}
if debug {
log.Printf("Leader %d with term %d is voting for server %d with term %d", pid, rserver.CurrentTerm, message.Pid, message.MsgId)
}
outbox <- &cluster.Envelope{Pid: message.Pid, MsgId: int64(rserver.CurrentTerm), Msg: ElectionStatusMessage{Term: rserver.CurrentTerm, Granted: true}}
rserver.RSLeader = false
rserver.State = FOLLOWER
rserver.VotedFor = msg.Term
break innerl
} else {
outbox <- &cluster.Envelope{Pid: message.Pid, MsgId: int64(rserver.CurrentTerm), Msg: ElectionStatusMessage{Term: rserver.CurrentTerm, Granted: false}}
}
}
// Received command from client
case message := <-rserver.Outer:
// Create a new Log Entry
if debug {
log.Printf("Received message %v", message)
}
logEntry := serverLogEntry{Index: rserver.CommitIndex + 1, ServerLogData: serverLogData{Term: rserver.CurrentTerm, Command: message}}
if debug {
log.Printf("CommitIndex of leader is %d", rserver.CommitIndex)
log.Printf("Created logEntry (%v) for message", logEntry)
}
rserver.Writer <- &logEntry
// Used to determine the success of follower commits
var count = 0
// Wait for the write to be successful
select {
case status := <-rserver.WriteSuccess:
if status {
count = count + 1
if debug {
log.Printf("Write succesful")
}
}
}
// Add the PrevLogTerm in the appendEntries message
var PrevLogTerm int
// Read Previous logEntry to ensure that it is in sync with the leader
rserver.ReaderRequest <- &ReadRequest{Index: rserver.CommitIndex}
// Wait for the logEntry to be read
select {
case serverLogEntry := <-rserver.ReaderData:
if debug {
log.Printf("Leader %d read logEntry %v", rserver.Pid, serverLogEntry)
}
if serverLogEntry != nil {
PrevLogTerm = serverLogEntry.ServerLogData.Term
}
}
// Now replicate this logEntry on all the followers
for peer := range peers {
peerId := peers[peer]
entries := []serverLogEntry{logEntry}
if debug {
log.Printf("Leader %d with term %d is sending entries to follower %d", pid, rserver.CurrentTerm, peerId)
}
appendEntries := AppendEntries{Term: rserver.CurrentTerm, LeaderId: pid, PrevLogIndex: rserver.CommitIndex, PrevLogTerm: PrevLogTerm, Entries: entries, LeaderCommit: rserver.CommitIndex}
outbox <- &cluster.Envelope{Pid: peerId, MsgId: int64(rserver.CurrentTerm), Msg: appendEntries}
}
// Wait for write success on majority
checkCommit:
for {
select {
case message := <-inbox:
switch msg := message.Msg.(type) {
case AppendEntriesStatus:
if msg.Term > rserver.CurrentTerm {
if debug {
log.Printf("Server %d with term %d is changing state from leader to follower", pid, rserver.CurrentTerm)
}
} else {
if msg.Success {
if count < cluster.Count() {
count = count + 1
// Majority of followers were able to log
if count >= cluster.Count()/2 {
// The commit was successful on all the followers
// Tell the client that the command has been written to the log with the index given in logEntry
if debug {
log.Printf("Sending success of write to client")
}
// Create a Log Entry for the Client
clogEntry := LogEntry{Index: logEntry.Index, Command: logEntry.ServerLogData.Command}
rserver.Inner <- &clogEntry
break checkCommit
}
}
}
}
case RequestVote:
if msg.Term >= rserver.CurrentTerm && msg.Term != rserver.VotedFor {
if debug {
log.Printf("Leader %d with term %d is changing state from leader to follower", pid, rserver.CurrentTerm)
}
if debug {
log.Printf("Leader %d with term %d is voting for server %d with term %d", pid, rserver.CurrentTerm, message.Pid, message.MsgId)
}
outbox <- &cluster.Envelope{Pid: message.Pid, MsgId: int64(rserver.CurrentTerm), Msg: ElectionStatusMessage{Term: rserver.CurrentTerm, Granted: true}}
rserver.RSLeader = false
rserver.State = FOLLOWER
rserver.VotedFor = msg.Term
break innerl
} else {
outbox <- &cluster.Envelope{Pid: message.Pid, MsgId: int64(rserver.CurrentTerm), Msg: ElectionStatusMessage{Term: rserver.CurrentTerm, Granted: false}}
}
case AppendEntries:
if msg.Term > rserver.CurrentTerm {
if debug {
log.Printf("Leader %d with term %d is changing state from leader to follower", pid, rserver.CurrentTerm)
}
rserver.RSLeader = false
rserver.State = FOLLOWER
inbox <- message
break innerl
}
}
// Retry after waiting for sometime
// case time.After(time.Second):
// break checkCommit
}
}
// Increment the commitIndex
if debug {
log.Printf("Incrementing commitIndex to %d", rserver.CommitIndex+1)
}
rserver.CommitIndex = rserver.CommitIndex + 1
appendEntries := AppendEntries{Term: rserver.CurrentTerm, LeaderId: pid, PrevLogIndex: rserver.CommitIndex, PrevLogTerm: PrevLogTerm, Entries: nil, LeaderCommit: rserver.CommitIndex}
for peer := range peers {
peerId := peers[peer]
if debug {
log.Printf("Leader %d with term %d Sending alive message to server %d", pid, rserver.CurrentTerm, peerId)
}
outbox <- &cluster.Envelope{Pid: peerId, MsgId: int64(rserver.CurrentTerm), Msg: appendEntries}
}
kvCommand := logEntry.ServerLogData.Command
switch cmd := kvCommand.(type) {
case KVCommand:
switch cmd.Command {
case PUT:
rserver.StateMachine[cmd.Key] = cmd.Value
case DEL:
delete(rserver.StateMachine, cmd.Key)
case GET:
// No action needs to be performed for GET
}
}
rserver.LastApplied = rserver.CommitIndex
case <-channelClose:
rserver.State = EXIT
break innerl
}
}
}
func candidateFunc(pid int, rserver *rServer, channelClose chan bool, inbox chan *cluster.Envelope, outbox chan *cluster.Envelope, peers []int, debug bool) {
var LastLogTerm int
// Read Previous logEntry to ensure that it is in sync with the leader
rserver.ReaderRequest <- &ReadRequest{Index: rserver.CommitIndex}
// Wait for the logEntry to be read
select {
case serverLogEntry := <-rserver.ReaderData:
if debug {
log.Printf("Candidate %d read logEntry %v", rserver.Pid, serverLogEntry)
}
if serverLogEntry != nil {
LastLogTerm = serverLogEntry.ServerLogData.Term
} else {
LastLogTerm = DEFAULT_TERM
}
}
requestVote := RequestVote{Term: rserver.CurrentTerm, CandidateId: pid, LastLogIndex: rserver.CommitIndex, LastLogTerm: LastLogTerm}
// Send request to become a leader to all the peers
for peer := range peers {
peerId := peers[peer]
if debug {
log.Printf("Server %d with term %d is sending request message to server %d", pid, rserver.CurrentTerm, peerId)
}
outbox <- &cluster.Envelope{Pid: peerId, MsgId: int64(rserver.CurrentTerm), Msg: requestVote}
}
// It will now wait for response from all the peers
var count int = 1 // Assume server votes for itself
innerc:
for {
select {
case message := <-inbox:
switch msg := message.Msg.(type) {
case ElectionStatusMessage:
if msg.Granted {
if debug {
log.Printf("server %d with term %d got vote from server %d with term %d", pid, rserver.CurrentTerm, message.Pid, message.MsgId)
}
count++
if count > cluster.Count()/2 {
// The candidate has won the election
// It should now act a leader and send alive messages to everyone
if debug {
log.Printf("server %d with term %d has now become a leader", pid, rserver.CurrentTerm)
}
rserver.CurrentTerm++
rserver.State = LEADER
rserver.RSLeader = true
break innerc
}
}
case AppendEntries:
// A new leader was elected
if msg.Term >= rserver.CurrentTerm {
// Change state to follower
if debug {
log.Printf("Server %d with term %d is changing state from candidate to follower", pid, rserver.CurrentTerm)
}
rserver.State = FOLLOWER
inbox <- message
break innerc
}
case RequestVote:
if msg.Term >= rserver.CurrentTerm && msg.Term > rserver.VotedFor {
if debug {
log.Printf("Server %d with term %d is changing state from candidate to follower", pid, rserver.CurrentTerm)
}
if debug {
log.Printf("server %d with term %d is voting for server %d with term %d", pid, rserver.CurrentTerm, message.Pid, message.MsgId)
}
outbox <- &cluster.Envelope{Pid: message.Pid, MsgId: int64(rserver.CurrentTerm), Msg: ElectionStatusMessage{Term: rserver.CurrentTerm, Granted: true}}
rserver.State = FOLLOWER
rserver.VotedFor = msg.Term
break innerc
} else {
outbox <- &cluster.Envelope{Pid: message.Pid, MsgId: int64(rserver.CurrentTerm), Msg: ElectionStatusMessage{Term: rserver.CurrentTerm, Granted: false}}
}
case LogEntry:
// This message is ignored by candidates at the moment
}
case <-time.After(time.Duration(int(time.Millisecond) * rserver.Timeout)):
rserver.State = CANDIDATE
rserver.CurrentTerm++
case <-channelClose:
rserver.State = EXIT
break innerc
}
}
}
