func (cli *EchoClient) Send(str string) (string, error) {
var args echoproto.Args
var reply echoproto.Reply
args.V = str
args.N = 1
werr := cli.rpcSvr.Call("Server.AppendLog", args, &reply)
if werr != nil {
fmt.Printf("Lost contact with server on write: %s\n", werr.Error())
return "", werr
}
fmt.Printf("echo client send replay %d %s\n", reply.Response, reply.Data[0])
return reply.Data[0], nil
}
// Initiate the Paxos protocol to append a new string to the log.
func (svr *Server) AppendLog(args *echoproto.Args, reply *echoproto.Reply) error {
var pargs echoproto.Args
var preply echoproto.Reply
var n_prepare, n_accept, n_error int
var err error
n_prepare = 0
n_accept = 0
log.Println("AppendLog(): Initiating Paxos protocol.")
for n_accept <= svr.F {
for n_prepare <= svr.F {
// initiate a commit to the log
svr.Lock.Lock()
// increment the Lamport timestamp and append the string to the log
svr.update()
pargs.N = svr.Time
svr.info("AppendLog()")
svr.Lock.Unlock()
n_prepare = 0
n_error = 0
for i := 0; i < len(svr.Peers); i++ {
err = svr.Peers[i].Call("Server.Prepare", pargs, &preply)
if err != nil {
log.Println("rpc.Call() error:", err)
n_error++
} else if preply.Response == echoproto.PREPARE_OK {
n_prepare++
}
}
if n_error > svr.F {
log.Fatalln("Too many failed nodes. No progress possible.")
}
if n_prepare <= svr.F {
log.Println("AppendLog(): Majority PREPARE_REJECT. Restarting Paxos.")
time.Sleep(1000 * time.Millisecond)
}
}
svr.Lock.Lock()
svr.info("AppendLog()")
log.Println("AppendLog(): Majority PREPARE_OK. Initiating accept phase.")
// n_prepare > svr.F
// continue with accept
if svr.V_accept == "" {
svr.V_accept = args.V
}
pargs.V = svr.V_accept
svr.Lock.Unlock()
n_accept = 0
n_error = 0
for i := 0; i < len(svr.Peers); i++ {
err = svr.Peers[i].Call("Server.Accept", pargs, &preply)
if err != nil {
log.Println("rpc.Call() error:", err)
n_error++
} else if preply.Response == echoproto.ACCEPT_OK {
n_accept++
}
}
if n_error > svr.F {
log.Fatalln("Too many failed nodes. No progress possible.")
}
if n_accept <= svr.F {
log.Println("AppendLog(): Majority ACCEPT_REJECT. Restarting Paxos.")
time.Sleep(1000 * time.Millisecond)
}
}
// n_accept > svr.F
// continue with commit
log.Println("AppendLog(): Majority ACCEPT_OK. Initiating commit phase.")
n_error = 0
for i := 0; i < len(svr.Peers); i++ {
err = svr.Peers[i].Call("Server.Commit", pargs, &preply)
if err != nil {
log.Println("rpc.Call() error:", err)
n_error++
}
}
if n_error > svr.F {
log.Fatalln("Too many failed nodes. No progress possible.")
}
svr.Commit(args, reply)
return nil
}
