func subscriber(srv *clonesrv_t) (err error) {
// Get state snapshot if necessary
if !srv.kvmap_init {
srv.kvmap_init = true
snapshot, _ := zmq.NewSocket(zmq.DEALER)
snapshot.Connect(fmt.Sprint("tcp://localhost:", srv.peer))
fmt.Printf("I: asking for snapshot from: tcp://localhost:%v\n", srv.peer)
snapshot.SendMessage("ICANHAZ?", "") // blank subtree to get all
for {
kvmsg, e := kvmsg.RecvKvmsg(snapshot)
if e != nil {
err = e
break
}
if key, _ := kvmsg.GetKey(); key == "KTHXBAI" {
srv.sequence, _ = kvmsg.GetSequence()
break // Done
}
kvmsg.Store(srv.kvmap)
}
fmt.Println("I: received snapshot =", srv.sequence)
}
// Find and remove update off pending list
kvmsg, e := kvmsg.RecvKvmsg(srv.subscriber)
if e != nil {
err = e
return
}
if key, _ := kvmsg.GetKey(); key != "HUGZ" {
if !srv.was_pending(kvmsg) {
// If active update came before client update, flip it
// around, store active update (with sequence) on pending
// list and use to clear client update when it comes later
srv.pending = append(srv.pending, kvmsg)
}
// If update is more recent than our kvmap, apply it
if seq, _ := kvmsg.GetSequence(); seq > srv.sequence {
srv.sequence = seq
kvmsg.Store(srv.kvmap)
fmt.Println("I: received update =", srv.sequence)
}
}
return
}
func clone_agent(pipename string) {
pipe, _ := zmq.NewSocket(zmq.PAIR)
pipe.Connect(pipename)
agent := agent_new(pipe)
LOOP:
for {
poller := zmq.NewPoller()
poller.Add(pipe, zmq.POLLIN)
server := agent.server[agent.cur_server]
switch agent.state {
case state_INITIAL:
// In this state we ask the server for a snapshot,
// if we have a server to talk to...
if agent.nbr_servers > 0 {
fmt.Printf("I: waiting for server at %s:%d...\n", server.address, server.port)
if server.requests < 2 {
server.snapshot.SendMessage("ICANHAZ?", agent.subtree)
server.requests++
}
server.expiry = time.Now().Add(server_TTL)
agent.state = state_SYNCING
poller.Add(server.snapshot, zmq.POLLIN)
}
case state_SYNCING:
// In this state we read from snapshot and we expect
// the server to respond, else we fail over.
poller.Add(server.snapshot, zmq.POLLIN)
case state_ACTIVE:
// In this state we read from subscriber and we expect
// the server to give hugz, else we fail over.
poller.Add(server.subscriber, zmq.POLLIN)
break
}
poll_timer := time.Duration(-1)
if server != nil {
poll_timer = server.expiry.Sub(time.Now())
if poll_timer < 0 {
poll_timer = 0
}
}
// We're ready to process incoming messages; if nothing at all
// comes from our server within the timeout, that means the
// server is dead:
polled, err := poller.Poll(poll_timer)
if err != nil {
break
}
if len(polled) > 0 {
for _, item := range polled {
switch socket := item.Socket; socket {
case pipe:
err = agent.control_message()
if err != nil {
break LOOP
}
default:
kvmsg, e := kvmsg.RecvKvmsg(socket)
if e != nil {
err = e
break LOOP
}
// Anything from server resets its expiry time
server.expiry = time.Now().Add(server_TTL)
if agent.state == state_SYNCING {
// Store in snapshot until we're finished
server.requests = 0
if key, _ := kvmsg.GetKey(); key == "KTHXBAI" {
agent.sequence, _ = kvmsg.GetSequence()
agent.state = state_ACTIVE
fmt.Printf("I: received from %s:%d snapshot=%d\n", server.address, server.port, agent.sequence)
} else {
kvmsg.Store(agent.kvmap)
}
} else if agent.state == state_ACTIVE {
// Discard out-of-sequence updates, incl. hugz
if seq, _ := kvmsg.GetSequence(); seq > agent.sequence {
agent.sequence = seq
kvmsg.Store(agent.kvmap)
fmt.Printf("I: received from %s:%d update=%d\n", server.address, server.port, agent.sequence)
}
}
}
}
} else {
// Server has died, failover to next
fmt.Printf("I: server at %s:%d didn't give hugz\n", server.address, server.port)
agent.cur_server = (agent.cur_server + 1) % agent.nbr_servers
agent.state = state_INITIAL
}
}
}
func main() {
snapshot, _ := zmq.NewSocket(zmq.DEALER)
snapshot.Connect("tcp://localhost:5556")
subscriber, _ := zmq.NewSocket(zmq.SUB)
subscriber.SetSubscribe(SUBTREE)
subscriber.Connect("tcp://localhost:5557")
publisher, _ := zmq.NewSocket(zmq.PUSH)
publisher.Connect("tcp://localhost:5558")
kvmap := make(map[string]*kvmsg.Kvmsg)
rand.Seed(time.Now().UnixNano())
// We first request a state snapshot:
sequence := int64(0)
snapshot.SendMessage("ICANHAZ?", SUBTREE)
for {
kvmsg, err := kvmsg.RecvKvmsg(snapshot)
if err != nil {
break // Interrupted
}
if key, _ := kvmsg.GetKey(); key == "KTHXBAI" {
sequence, _ := kvmsg.GetSequence()
fmt.Println("I: received snapshot =", sequence)
break // Done
}
kvmsg.Store(kvmap)
}
snapshot.Close()
poller := zmq.NewPoller()
poller.Add(subscriber, zmq.POLLIN)
alarm := time.Now().Add(1000 * time.Millisecond)
for {
tickless := alarm.Sub(time.Now())
if tickless < 0 {
tickless = 0
}
polled, err := poller.Poll(tickless)
if err != nil {
break // Context has been shut down
}
if len(polled) == 1 {
kvmsg, err := kvmsg.RecvKvmsg(subscriber)
if err != nil {
break // Interrupted
}
// Discard out-of-sequence kvmsgs, incl. heartbeats
if seq, _ := kvmsg.GetSequence(); seq > sequence {
sequence = seq
kvmsg.Store(kvmap)
fmt.Println("I: received update =", sequence)
}
}
// If we timed-out, generate a random kvmsg
if time.Now().After(alarm) {
kvmsg := kvmsg.NewKvmsg(0)
kvmsg.SetKey(fmt.Sprintf("%s%d", SUBTREE, rand.Intn(10000)))
kvmsg.SetBody(fmt.Sprint(rand.Intn(1000000)))
kvmsg.SetProp("ttl", fmt.Sprintf("%d", rand.Intn((30)))) // seconds
kvmsg.Send(publisher)
alarm = time.Now().Add(1000 * time.Millisecond)
}
}
fmt.Printf("Interrupted\n%d messages in\n", sequence)
}