// Used to check for existence of server
func Exists(pid int, debug bool) bool {
if cluster.Exists(pid, debug) {
return true
} else {
return false
}
}
// The main server routine
func serverRoutine(pid int, rserver *rServer, config string, channelClose chan bool, debug bool) {
// Retrieve term,votedFor,start and commit Index for this server
err := retrieveData(rserver)
// Apply the commands in the log to the state machine
for index := rserver.StartIndex; index <= rserver.CommitIndex; index++ {
rserver.ReaderRequest <- &ReadRequest{Index: index}
// Wait for the logEntry to be read
select {
case serverLogEntry := <-rserver.ReaderData:
if debug {
log.Printf("Server %d read logEntry %v for index %v", rserver.Pid, serverLogEntry, index)
}
if serverLogEntry != nil {
if debug {
log.Printf("Applying %v to StateMachine of server %d", serverLogEntry.ServerLogData.Command, pid)
}
kvCommand := serverLogEntry.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 = index
}
}
}
// Check if server already exists
if cluster.Exists(pid, debug) {
if debug {
log.Printf("Server %d already exists", pid)
}
// If a server is already present, then return
return
}
// This will start a new server
cserver := cluster.New(pid, config, debug)
// A server starts of as a follower
rserver.State = FOLLOWER
if err != nil {
if debug {
log.Printf("Error in Server %d: %v", rserver.Pid, err)
}
}
// Print server timeout
if debug {
log.Printf("Timeout for server with pid %d is %d", pid, rserver.Timeout)
}
if err != nil {
if debug {
log.Printf("Error while reading persistant data for %d", pid)
}
// Set the term to the default value
rserver.CurrentTerm = DEFAULT_TERM
}
outer:
for {
// A server will be in one of the three states at any moment
switch rserver.State {
// Describes what the server will do when in the follower state
case FOLLOWER:
if debug {
log.Printf("Server %d with term %d is executing as follower", pid, rserver.CurrentTerm)
}
followerFunc(pid, rserver, channelClose, cserver.Inbox(), cserver.Outbox(), debug)
// Describes the behavior of a candidate
case CANDIDATE:
if debug {
log.Printf("Server %d with term %d is executing as candidate", pid, rserver.CurrentTerm)
}
candidateFunc(pid, rserver, channelClose, cserver.Inbox(), cserver.Outbox(), cserver.Peers(), debug)
// Describes the behavior of a leader
case LEADER:
if debug {
log.Printf("Server %d with term %d is executing as leader", pid, rserver.CurrentTerm)
}
leaderFunc(pid, rserver, channelClose, cserver.Inbox(), cserver.Outbox(), cserver.Peers(), debug)
case EXIT:
if debug {
log.Printf("Server %d with term %d is preparing to shutdown", pid, rserver.State)
}
// close the db writer
rserver.HandlerClose <- true
if debug {
log.Printf("Sending close signal to dbHandler")
}
break outer
}
}
err = persistData(rserver)
if err != nil {
log.Printf("Error in Server %d: %v", rserver.Pid, err)
}
rserver.RSLeader = false
cluster.Close(cserver, debug)
// time.Sleep(time.Millisecond)
if debug {
log.Printf("Shutting down server with id %d", pid)
}
}